5
This document describes the Bazaar internals and the development process.
6
It's meant for people interested in developing Bazaar, and some parts will
7
also be useful to people developing Bazaar plugins.
9
If you have any questions or something seems to be incorrect, unclear or
10
missing, please talk to us in ``irc://irc.freenode.net/#bzr``, or write to
11
the Bazaar mailing list. To propose a correction or addition to this
12
document, send a merge request or new text to the mailing list.
14
The current version of this document is available in the file
15
``doc/developers/HACKING.txt`` in the source tree, or at
16
http://doc.bazaar-vcs.org/bzr.dev/en/developer-guide/HACKING.html
19
`Bazaar Developer Documentation Catalog <../../developers/index.html>`_.
27
Exploring the Bazaar Platform
28
=============================
30
Before making changes, it's a good idea to explore the work already
31
done by others. Perhaps the new feature or improvement you're looking
32
for is available in another plug-in already? If you find a bug,
33
perhaps someone else has already fixed it?
35
To answer these questions and more, take a moment to explore the
36
overall Bazaar Platform. Here are some links to browse:
38
* The Plugins page on the Wiki - http://bazaar-vcs.org/BzrPlugins
40
* The Bazaar product family on Launchpad - https://launchpad.net/bazaar
42
* Bug Tracker for the core product - https://bugs.launchpad.net/bzr/
44
* Blueprint Tracker for the core product - https://blueprints.launchpad.net/bzr/
46
If nothing else, perhaps you'll find inspiration in how other developers
47
have solved their challenges.
50
Planning and Discussing Changes
51
===============================
53
There is a very active community around Bazaar. Mostly we meet on IRC
54
(#bzr on irc.freenode.net) and on the mailing list. To join the Bazaar
55
community, see http://bazaar-vcs.org/BzrSupport.
57
If you are planning to make a change, it's a very good idea to mention it
58
on the IRC channel and/or on the mailing list. There are many advantages
59
to involving the community before you spend much time on a change.
62
* you get to build on the wisdom on others, saving time
64
* if others can direct you to similar code, it minimises the work to be done
66
* it assists everyone in coordinating direction, priorities and effort.
68
In summary, maximising the input from others typically minimises the
69
total effort required to get your changes merged. The community is
70
friendly, helpful and always keen to welcome newcomers.
73
Bazaar Development in a Nutshell
74
================================
76
Looking for a 10 minute introduction to submitting a change?
77
See http://bazaar-vcs.org/BzrGivingBack.
79
TODO: Merge that Wiki page into this document.
82
Understanding the Development Process
83
=====================================
85
The development team follows many best-practices including:
87
* a public roadmap and planning process in which anyone can participate
89
* time based milestones everyone can work towards and plan around
91
* extensive code review and feedback to contributors
93
* complete and rigorous test coverage on any code contributed
95
* automated validation that all tests still pass before code is merged
96
into the main code branch.
98
The key tools we use to enable these practices are:
100
* Launchpad - https://launchpad.net/
102
* Bazaar - http://bazaar-vcs.org/
104
* Bundle Buggy - http://bundlebuggy.aaronbentley.com/
106
* Patch Queue Manager - https://launchpad.net/pqm/
108
For further information, see http://bazaar-vcs.org/BzrDevelopment.
111
A Closer Look at the Merge & Review Process
112
===========================================
114
If you'd like to propose a change, please post to the
115
bazaar@lists.canonical.com list with a bundle, patch, or link to a
116
branch. Put '[PATCH]' or '[MERGE]' in the subject so Bundle Buggy
117
can pick it out, and explain the change in the email message text.
118
Remember to update the NEWS file as part of your change if it makes any
119
changes visible to users or plugin developers. Please include a diff
120
against mainline if you're giving a link to a branch.
122
You can generate a bundle like this::
124
bzr bundle > mybundle.patch
126
A .patch extension is recommended instead of .bundle as many mail clients
127
will send the latter as a binary file. If a bundle would be too long or your
128
mailer mangles whitespace (e.g. implicitly converts Unix newlines to DOS
129
newlines), use the merge-directive command instead like this::
131
bzr merge-directive http://bazaar-vcs.org http://example.org/my_branch > my_directive.patch
133
See the help for details on the arguments to merge-directive.
135
Please do **NOT** put [PATCH] or [MERGE] in the subject line if you don't
136
want it to be merged. If you want comments from developers rather than
137
to be merged, you can put '[RFC]' in the subject line.
139
Anyone is welcome to review code. There are broadly three gates for
142
* Doesn't reduce test coverage: if it adds new methods or commands,
143
there should be tests for them. There is a good test framework
144
and plenty of examples to crib from, but if you are having trouble
145
working out how to test something feel free to post a draft patch
148
* Doesn't reduce design clarity, such as by entangling objects
149
we're trying to separate. This is mostly something the more
150
experienced reviewers need to help check.
152
* Improves bugs, features, speed, or code simplicity.
154
Code that goes in should pass all three. The core developers take care
155
to keep the code quality high and understandable while recognising that
156
perfect is sometimes the enemy of good. (It is easy for reviews to make
157
people notice other things which should be fixed but those things should
158
not hold up the original fix being accepted. New things can easily be
159
recorded in the Bug Tracker instead.)
161
Anyone can "vote" on the mailing list. Core developers can also vote using
162
Bundle Buggy. Here are the voting codes and their explanations.
164
:approve: Reviewer wants this submission merged.
165
:tweak: Reviewer wants this submission merged with small changes. (No
167
:abstain: Reviewer does not intend to vote on this patch.
168
:resubmit: Please make changes and resubmit for review.
169
:reject: Reviewer doesn't want this kind of change merged.
170
:comment: Not really a vote. Reviewer just wants to comment, for now.
172
If a change gets two approvals from core reviewers, and no rejections,
173
then it's OK to come in. Any of the core developers can bring it into the
174
bzr.dev trunk and backport it to maintenance branches if required. The
175
Release Manager will merge the change into the branch for a pending
176
release, if any. As a guideline, core developers usually merge their own
177
changes and volunteer to merge other contributions if they were the second
178
reviewer to agree to a change.
180
To track the progress of proposed changes, use Bundle Buggy. See
181
http://bundlebuggy.aaronbentley.com/help for a link to all the
182
outstanding merge requests together with an explanation of the columns.
183
Bundle Buggy will also mail you a link to track just your change.
186
Preparing a Sandbox for Making Changes to Bazaar
187
================================================
189
Bazaar supports many ways of organising your work. See
190
http://bazaar-vcs.org/SharedRepositoryLayouts for a summary of the
191
popular alternatives.
193
Of course, the best choice for you will depend on numerous factors:
194
the number of changes you may be making, the complexity of the changes, etc.
195
As a starting suggestion though:
197
* create a local copy of the main development branch (bzr.dev) by using
200
bzr branch http://bazaar-vcs.org/bzr/bzr.dev/ bzr.dev
202
* keep your copy of bzr.dev prestine (by not developing in it) and keep
203
it up to date (by using bzr pull)
205
* create a new branch off your local bzr.dev copy for each issue
206
(bug or feature) you are working on.
208
This approach makes it easy to go back and make any required changes
209
after a code review. Resubmitting the change is then simple with no
210
risk of accidentially including edits related to other issues you may
211
be working on. After the changes for an issue are accepted and merged,
212
the associated branch can be deleted or archived as you wish.
215
Navigating the Code Base
216
========================
218
.. Was at <http://bazaar-vcs.org/NewDeveloperIntroduction>
220
Some of the key files in this directory are:
223
The command you run to start Bazaar itself. This script is pretty
224
short and just does some checks then jumps into bzrlib.
227
This file covers a brief introduction to Bazaar and lists some of its
231
Summary of changes in each Bazaar release that can affect users or
235
Installs Bazaar system-wide or to your home directory. To perform
236
development work on Bazaar it is not required to run this file - you
237
can simply run the bzr command from the top level directory of your
238
development copy. Note: That if you run setup.py this will create a
239
'build' directory in your development branch. There's nothing wrong
240
with this but don't be confused by it. The build process puts a copy
241
of the main code base into this build directory, along with some other
242
files. You don't need to go in here for anything discussed in this
246
Possibly the most exciting folder of all, bzrlib holds the main code
247
base. This is where you will go to edit python files and contribute to
251
Holds documentation on a whole range of things on Bazaar from the
252
origination of ideas within the project to information on Bazaar
253
features and use cases. Within this directory there is a subdirectory
254
for each translation into a human language. All the documentation
255
is in the ReStructuredText markup language.
258
Documentation specifically targetted at Bazaar and plugin developers.
259
(Including this document.)
263
Automatically-generated API reference information is available at
264
<http://starship.python.net/crew/mwh/bzrlibapi/>.
265
(There is an experimental editable version at
266
<http://starship.python.net/crew/mwh/bzrlibapi-oe/>.)
267
See also the `Essential Domain Classes`_
268
section of this guide.
274
The Importance of Testing
275
=========================
277
Reliability is a critical success factor for any Version Control System.
278
We want Bazaar to be highly reliable across multiple platforms while
279
evolving over time to meet the needs of its community.
281
In a nutshell, this is want we expect and encourage:
283
* New functionality should have test cases. Preferably write the
284
test before writing the code.
286
In general, you can test at either the command-line level or the
287
internal API level. See Writing tests below for more detail.
289
* Try to practice Test-Driven Development: before fixing a bug, write a
290
test case so that it does not regress. Similarly for adding a new
291
feature: write a test case for a small version of the new feature before
292
starting on the code itself. Check the test fails on the old code, then
293
add the feature or fix and check it passes.
295
By doing these things, the Bazaar team gets increased confidence that
296
changes do what they claim to do, whether provided by the core team or
297
by community members. Equally importantly, we can be surer that changes
298
down the track do not break new features or bug fixes that you are
301
As of May 2008, Bazaar ships with a test suite containing over 12000 tests
302
and growing. We are proud of it and want to remain so. As community
303
members, we all benefit from it. Would you trust version control on
304
your project to a product *without* a test suite like Bazaar has?
307
Running the Test Suite
308
======================
310
Currently, bzr selftest is used to invoke tests.
311
You can provide a pattern argument to run a subset. For example,
312
to run just the blackbox tests, run::
314
./bzr selftest -v blackbox
316
To skip a particular test (or set of tests), use the --exclude option
317
(shorthand -x) like so::
319
./bzr selftest -v -x blackbox
321
To ensure that all tests are being run and succeeding, you can use the
322
--strict option which will fail if there are any missing features or known
325
./bzr selftest --strict
327
To list tests without running them, use the --list-only option like so::
329
./bzr selftest --list-only
331
This option can be combined with other selftest options (like -x) and
332
filter patterns to understand their effect.
334
Once you understand how to create a list of tests, you can use the --load-list
335
option to run only a restricted set of tests that you kept in a file, one test
336
id by line. Keep in mind that this will never be sufficient to validate your
337
modifications, you still need to run the full test suite for that, but using it
338
can help in some cases (like running only the failed tests for some time)::
340
./bzr selftest -- load-list my_failing_tests
342
This option can also be combined with other selftest options, including
343
patterns. It has some drawbacks though, the list can become out of date pretty
344
quick when doing Test Driven Development.
346
To address this concern, there is another way to run a restricted set of tests:
347
the --starting-with option will run only the tests whose name starts with the
348
specified string. It will also avoid loading the other tests and as a
349
consequence starts running your tests quicker::
351
./bzr selftest --starting-with bzrlib.blackbox
353
This option can be combined with all the other selftest options including
354
--load-list. The later is rarely used but allows to run a subset of a list of
355
failing tests for example.
357
Test suite debug flags
358
----------------------
360
Similar to the global ``-Dfoo`` debug options, bzr selftest accepts
361
``-E=foo`` debug flags. These flags are:
363
:allow_debug: do *not* clear the global debug flags when running a test.
364
This can provide useful logging to help debug test failures when used
365
with e.g. ``bzr -Dhpss selftest -E=allow_debug``
371
In general tests should be placed in a file named test_FOO.py where
372
FOO is the logical thing under test. That file should be placed in the
373
tests subdirectory under the package being tested.
375
For example, tests for merge3 in bzrlib belong in bzrlib/tests/test_merge3.py.
376
See bzrlib/tests/test_sampler.py for a template test script.
378
Tests can be written for the UI or for individual areas of the library.
379
Choose whichever is appropriate: if adding a new command, or a new command
380
option, then you should be writing a UI test. If you are both adding UI
381
functionality and library functionality, you will want to write tests for
382
both the UI and the core behaviours. We call UI tests 'blackbox' tests
383
and they are found in ``bzrlib/tests/blackbox/*.py``.
385
When writing blackbox tests please honour the following conventions:
387
1. Place the tests for the command 'name' in
388
bzrlib/tests/blackbox/test_name.py. This makes it easy for developers
389
to locate the test script for a faulty command.
391
2. Use the 'self.run_bzr("name")' utility function to invoke the command
392
rather than running bzr in a subprocess or invoking the
393
cmd_object.run() method directly. This is a lot faster than
394
subprocesses and generates the same logging output as running it in a
395
subprocess (which invoking the method directly does not).
397
3. Only test the one command in a single test script. Use the bzrlib
398
library when setting up tests and when evaluating the side-effects of
399
the command. We do this so that the library api has continual pressure
400
on it to be as functional as the command line in a simple manner, and
401
to isolate knock-on effects throughout the blackbox test suite when a
402
command changes its name or signature. Ideally only the tests for a
403
given command are affected when a given command is changed.
405
4. If you have a test which does actually require running bzr in a
406
subprocess you can use ``run_bzr_subprocess``. By default the spawned
407
process will not load plugins unless ``--allow-plugins`` is supplied.
413
We make selective use of doctests__. In general they should provide
414
*examples* within the API documentation which can incidentally be tested. We
415
don't try to test every important case using doctests -- regular Python
416
tests are generally a better solution.
418
Most of these are in ``bzrlib/doc/api``. More additions are welcome.
420
__ http://docs.python.org/lib/module-doctest.html
423
Skipping tests and test requirements
424
------------------------------------
426
In our enhancements to unittest we allow for some addition results beyond
427
just success or failure.
429
If a test can't be run, it can say that it's skipped. This is typically
430
used in parameterized tests - for example if a transport doesn't support
431
setting permissions, we'll skip the tests that relating to that. ::
434
return self.branch_format.initialize(repo.bzrdir)
435
except errors.UninitializableFormat:
436
raise tests.TestSkipped('Uninitializable branch format')
438
Raising TestSkipped is a good idea when you want to make it clear that the
439
test was not run, rather than just returning which makes it look as if it
442
Several different cases are distinguished:
445
Generic skip; the only type that was present up to bzr 0.18.
448
The test doesn't apply to the parameters with which it was run.
449
This is typically used when the test is being applied to all
450
implementations of an interface, but some aspects of the interface
451
are optional and not present in particular concrete
452
implementations. (Some tests that should raise this currently
453
either silently return or raise TestSkipped.) Another option is
454
to use more precise parameterization to avoid generating the test
458
**(Not implemented yet)**
459
The test can't be run because of an inherent limitation of the
460
environment, such as not having symlinks or not supporting
464
The test can't be run because a dependency (typically a Python
465
library) is not available in the test environment. These
466
are in general things that the person running the test could fix
467
by installing the library. It's OK if some of these occur when
468
an end user runs the tests or if we're specifically testing in a
469
limited environment, but a full test should never see them.
472
The test exists but is known to fail, for example because the
473
code to fix it hasn't been run yet. Raising this allows
474
you to distinguish these failures from the ones that are not
475
expected to fail. This could be conditionally raised if something
476
is broken on some platforms but not on others.
478
If the test would fail because of something we don't expect or
479
intend to fix, KnownFailure is not appropriate, and
480
TestNotApplicable might be better.
482
We plan to support three modes for running the test suite to control the
483
interpretation of these results. Strict mode is for use in situations
484
like merges to the mainline and releases where we want to make sure that
485
everything that can be tested has been tested. Lax mode is for use by
486
developers who want to temporarily tolerate some known failures. The
487
default behaviour is obtained by ``bzr selftest`` with no options, and
488
also (if possible) by running under another unittest harness.
490
======================= ======= ======= ========
491
result strict default lax
492
======================= ======= ======= ========
493
TestSkipped pass pass pass
494
TestNotApplicable pass pass pass
495
TestPlatformLimit pass pass pass
496
TestDependencyMissing fail pass pass
497
KnownFailure fail pass pass
498
======================= ======= ======= ========
501
Test feature dependencies
502
-------------------------
504
Rather than manually checking the environment in each test, a test class
505
can declare its dependence on some test features. The feature objects are
506
checked only once for each run of the whole test suite.
508
For historical reasons, as of May 2007 many cases that should depend on
509
features currently raise TestSkipped.)
513
class TestStrace(TestCaseWithTransport):
515
_test_needs_features = [StraceFeature]
517
This means all tests in this class need the feature. The feature itself
518
should provide a ``_probe`` method which is called once to determine if
521
These should generally be equivalent to either TestDependencyMissing or
522
sometimes TestPlatformLimit.
528
Known failures are when a test exists but we know it currently doesn't
529
work, allowing the test suite to still pass. These should be used with
530
care, we don't want a proliferation of quietly broken tests. It might be
531
appropriate to use them if you've committed a test for a bug but not the
532
fix for it, or if something works on Unix but not on Windows.
535
Testing exceptions and errors
536
-----------------------------
538
It's important to test handling of errors and exceptions. Because this
539
code is often not hit in ad-hoc testing it can often have hidden bugs --
540
it's particularly common to get NameError because the exception code
541
references a variable that has since been renamed.
543
.. TODO: Something about how to provoke errors in the right way?
545
In general we want to test errors at two levels:
547
1. A test in ``test_errors.py`` checking that when the exception object is
548
constructed with known parameters it produces an expected string form.
549
This guards against mistakes in writing the format string, or in the
550
``str`` representations of its parameters. There should be one for
551
each exception class.
553
2. Tests that when an api is called in a particular situation, it raises
554
an error of the expected class. You should typically use
555
``assertRaises``, which in the Bazaar test suite returns the exception
556
object to allow you to examine its parameters.
558
In some cases blackbox tests will also want to check error reporting. But
559
it can be difficult to provoke every error through the commandline
560
interface, so those tests are only done as needed -- eg in response to a
561
particular bug or if the error is reported in an unusual way(?) Blackbox
562
tests should mostly be testing how the command-line interface works, so
563
should only test errors if there is something particular to the cli in how
564
they're displayed or handled.
570
The Python ``warnings`` module is used to indicate a non-fatal code
571
problem. Code that's expected to raise a warning can be tested through
574
The test suite can be run with ``-Werror`` to check no unexpected errors
577
However, warnings should be used with discretion. It's not an appropriate
578
way to give messages to the user, because the warning is normally shown
579
only once per source line that causes the problem. You should also think
580
about whether the warning is serious enought that it should be visible to
581
users who may not be able to fix it.
584
Interface implementation testing and test scenarios
585
---------------------------------------------------
587
There are several cases in Bazaar of multiple implementations of a common
588
conceptual interface. ("Conceptual" because
589
it's not necessary for all the implementations to share a base class,
590
though they often do.) Examples include transports and the working tree,
591
branch and repository classes.
593
In these cases we want to make sure that every implementation correctly
594
fulfils the interface requirements. For example, every Transport should
595
support the ``has()`` and ``get()`` and ``clone()`` methods. We have a
596
sub-suite of tests in ``test_transport_implementations``. (Most
597
per-implementation tests are in submodules of ``bzrlib.tests``, but not
598
the transport tests at the moment.)
600
These tests are repeated for each registered Transport, by generating a
601
new TestCase instance for the cross product of test methods and transport
602
implementations. As each test runs, it has ``transport_class`` and
603
``transport_server`` set to the class it should test. Most tests don't
604
access these directly, but rather use ``self.get_transport`` which returns
605
a transport of the appropriate type.
607
The goal is to run per-implementation only tests that relate to that
608
particular interface. Sometimes we discover a bug elsewhere that happens
609
with only one particular transport. Once it's isolated, we can consider
610
whether a test should be added for that particular implementation,
611
or for all implementations of the interface.
613
The multiplication of tests for different implementations is normally
614
accomplished by overriding the ``test_suite`` function used to load
615
tests from a module. This function typically loads all the tests,
616
then applies a TestProviderAdapter to them, which generates a longer
617
suite containing all the test variations.
623
Some utilities are provided for generating variations of tests. This can
624
be used for per-implementation tests, or other cases where the same test
625
code needs to run several times on different scenarios.
627
The general approach is to define a class that provides test methods,
628
which depend on attributes of the test object being pre-set with the
629
values to which the test should be applied. The test suite should then
630
also provide a list of scenarios in which to run the tests.
632
Typically ``multiply_tests_from_modules`` should be called from the test
633
module's ``test_suite`` function.
636
Essential Domain Classes
637
########################
639
Introducing the Object Model
640
============================
642
The core domain objects within the bazaar model are:
652
Transports are explained below. See http://bazaar-vcs.org/Classes/
653
for an introduction to the other key classes.
658
The ``Transport`` layer handles access to local or remote directories.
659
Each Transport object acts like a logical connection to a particular
660
directory, and it allows various operations on files within it. You can
661
*clone* a transport to get a new Transport connected to a subdirectory or
664
Transports are not used for access to the working tree. At present
665
working trees are always local and they are accessed through the regular
666
Python file io mechanisms.
671
Transports work in URLs. Take note that URLs are by definition only
672
ASCII - the decision of how to encode a Unicode string into a URL must be
673
taken at a higher level, typically in the Store. (Note that Stores also
674
escape filenames which cannot be safely stored on all filesystems, but
675
this is a different level.)
677
The main reason for this is that it's not possible to safely roundtrip a
678
URL into Unicode and then back into the same URL. The URL standard
679
gives a way to represent non-ASCII bytes in ASCII (as %-escapes), but
680
doesn't say how those bytes represent non-ASCII characters. (They're not
681
guaranteed to be UTF-8 -- that is common but doesn't happen everywhere.)
683
For example if the user enters the url ``http://example/%e0`` there's no
684
way to tell whether that character represents "latin small letter a with
685
grave" in iso-8859-1, or "latin small letter r with acute" in iso-8859-2
686
or malformed UTF-8. So we can't convert their URL to Unicode reliably.
688
Equally problematic if we're given a url-like string containing non-ascii
689
characters (such as the accented a) we can't be sure how to convert that
690
to the correct URL, because we don't know what encoding the server expects
691
for those characters. (Although this is not totally reliable we might still
692
accept these and assume they should be put into UTF-8.)
694
A similar edge case is that the url ``http://foo/sweet%2Fsour`` contains
695
one directory component whose name is "sweet/sour". The escaped slash is
696
not a directory separator. If we try to convert URLs to regular Unicode
697
paths this information will be lost.
699
This implies that Transports must natively deal with URLs; for simplicity
700
they *only* deal with URLs and conversion of other strings to URLs is done
701
elsewhere. Information they return, such as from ``list_dir``, is also in
702
the form of URL components.
705
Coding Style Guidelines
706
#######################
711
``hasattr`` should not be used because it swallows exceptions including
712
``KeyboardInterrupt``. Instead, say something like ::
714
if getattr(thing, 'name', None) is None
720
Please write PEP-8__ compliant code.
722
__ http://www.python.org/peps/pep-0008.html
724
One often-missed requirement is that the first line of docstrings
725
should be a self-contained one-sentence summary.
727
We use 4 space indents for blocks, and never use tab characters. (In vim,
730
Lines should be no more than 79 characters if at all possible.
731
Lines that continue a long statement may be indented in either of
734
within the parenthesis or other character that opens the block, e.g.::
740
or indented by four spaces::
746
The first is considered clearer by some people; however it can be a bit
747
harder to maintain (e.g. when the method name changes), and it does not
748
work well if the relevant parenthesis is already far to the right. Avoid
751
self.legbone.kneebone.shinbone.toebone.shake_it(one,
757
self.legbone.kneebone.shinbone.toebone.shake_it(one,
763
self.legbone.kneebone.shinbone.toebone.shake_it(
766
For long lists, we like to add a trailing comma and put the closing
767
character on the following line. This makes it easier to add new items in
770
from bzrlib.goo import (
776
There should be spaces between function paramaters, but not between the
777
keyword name and the value::
779
call(1, 3, cheese=quark)
783
;(defface my-invalid-face
784
; '((t (:background "Red" :underline t)))
785
; "Face used to highlight invalid constructs or other uglyties"
788
(defun my-python-mode-hook ()
789
;; setup preferred indentation style.
790
(setq fill-column 79)
791
(setq indent-tabs-mode nil) ; no tabs, never, I will not repeat
792
; (font-lock-add-keywords 'python-mode
793
; '(("^\\s *\t" . 'my-invalid-face) ; Leading tabs
794
; ("[ \t]+$" . 'my-invalid-face) ; Trailing spaces
795
; ("^[ \t]+$" . 'my-invalid-face)); Spaces only
799
(add-hook 'python-mode-hook 'my-python-mode-hook)
801
The lines beginning with ';' are comments. They can be activated
802
if one want to have a strong notice of some tab/space usage
809
* Imports should be done at the top-level of the file, unless there is
810
a strong reason to have them lazily loaded when a particular
811
function runs. Import statements have a cost, so try to make sure
812
they don't run inside hot functions.
814
* Module names should always be given fully-qualified,
815
i.e. ``bzrlib.hashcache`` not just ``hashcache``.
821
Functions, methods or members that are "private" to bzrlib are given
822
a leading underscore prefix. Names without a leading underscore are
823
public not just across modules but to programmers using bzrlib as an
824
API. As a consequence, a leading underscore is appropriate for names
825
exposed across modules but that are not to be exposed to bzrlib API
828
We prefer class names to be concatenated capital words (``TestCase``)
829
and variables, methods and functions to be lowercase words joined by
830
underscores (``revision_id``, ``get_revision``).
832
For the purposes of naming some names are treated as single compound
833
words: "filename", "revno".
835
Consider naming classes as nouns and functions/methods as verbs.
837
Try to avoid using abbreviations in names, because there can be
838
inconsistency if other people use the full name.
844
``revision_id`` not ``rev_id`` or ``revid``
846
Functions that transform one thing to another should be named ``x_to_y``
847
(not ``x2y`` as occurs in some old code.)
853
Python destructors (``__del__``) work differently to those of other
854
languages. In particular, bear in mind that destructors may be called
855
immediately when the object apparently becomes unreferenced, or at some
856
later time, or possibly never at all. Therefore we have restrictions on
857
what can be done inside them.
859
0. If you think you need to use a ``__del__`` method ask another
860
developer for alternatives. If you do need to use one, explain
863
1. Never rely on a ``__del__`` method running. If there is code that
864
must run, do it from a ``finally`` block instead.
866
2. Never ``import`` from inside a ``__del__`` method, or you may crash the
869
3. In some places we raise a warning from the destructor if the object
870
has not been cleaned up or closed. This is considered OK: the warning
871
may not catch every case but it's still useful sometimes.
877
In some places we have variables which point to callables that construct
878
new instances. That is to say, they can be used a lot like class objects,
879
but they shouldn't be *named* like classes:
881
> I think that things named FooBar should create instances of FooBar when
882
> called. Its plain confusing for them to do otherwise. When we have
883
> something that is going to be used as a class - that is, checked for via
884
> isinstance or other such idioms, them I would call it foo_class, so that
885
> it is clear that a callable is not sufficient. If it is only used as a
886
> factory, then yes, foo_factory is what I would use.
892
Several places in Bazaar use (or will use) a registry, which is a
893
mapping from names to objects or classes. The registry allows for
894
loading in registered code only when it's needed, and keeping
895
associated information such as a help string or description.
898
InterObject and multiple dispatch
899
=================================
901
The ``InterObject`` provides for two-way `multiple dispatch`__: matching
902
up for example a source and destination repository to find the right way
903
to transfer data between them.
905
.. __: http://en.wikipedia.org/wiki/Multiple_dispatch
907
There is a subclass ``InterObject`` classes for each type of object that is
908
dispatched this way, e.g. ``InterRepository``. Calling ``.get()`` on this
909
class will return an ``InterObject`` instance providing the best match for
910
those parameters, and this instance then has methods for operations
913
inter = InterRepository.get(source_repo, target_repo)
914
inter.fetch(revision_id)
916
``InterRepository`` also acts as a registry-like object for its
917
subclasses, and they can be added through ``.register_optimizer``. The
918
right one to run is selected by asking each class, in reverse order of
919
registration, whether it ``.is_compatible`` with the relevant objects.
924
To make startup time faster, we use the ``bzrlib.lazy_import`` module to
925
delay importing modules until they are actually used. ``lazy_import`` uses
926
the same syntax as regular python imports. So to import a few modules in a
929
from bzrlib.lazy_import import lazy_import
930
lazy_import(globals(), """
939
revision as _mod_revision,
941
import bzrlib.transport
945
At this point, all of these exist as a ``ImportReplacer`` object, ready to
946
be imported once a member is accessed. Also, when importing a module into
947
the local namespace, which is likely to clash with variable names, it is
948
recommended to prefix it as ``_mod_<module>``. This makes it clearer that
949
the variable is a module, and these object should be hidden anyway, since
950
they shouldn't be imported into other namespaces.
952
While it is possible for ``lazy_import()`` to import members of a module
953
when using the ``from module import member`` syntax, it is recommended to
954
only use that syntax to load sub modules ``from module import submodule``.
955
This is because variables and classes can frequently be used without
956
needing a sub-member for example::
958
lazy_import(globals(), """
959
from module import MyClass
963
return isinstance(x, MyClass)
965
This will incorrectly fail, because ``MyClass`` is a ``ImportReplacer``
966
object, rather than the real class.
968
It also is incorrect to assign ``ImportReplacer`` objects to other variables.
969
Because the replacer only knows about the original name, it is unable to
970
replace other variables. The ``ImportReplacer`` class will raise an
971
``IllegalUseOfScopeReplacer`` exception if it can figure out that this
972
happened. But it requires accessing a member more than once from the new
973
variable, so some bugs are not detected right away.
979
The null revision is the ancestor of all revisions. Its revno is 0, its
980
revision-id is ``null:``, and its tree is the empty tree. When referring
981
to the null revision, please use ``bzrlib.revision.NULL_REVISION``. Old
982
code sometimes uses ``None`` for the null revision, but this practice is
986
Object string representations
987
=============================
989
Python prints objects using their ``__repr__`` method when they are
990
written to logs, exception tracebacks, or the debugger. We want
991
objects to have useful representations to help in determining what went
994
If you add a new class you should generally add a ``__repr__`` method
995
unless there is an adequate method in a parent class. There should be a
998
Representations should typically look like Python constructor syntax, but
999
they don't need to include every value in the object and they don't need
1000
to be able to actually execute. They're to be read by humans, not
1001
machines. Don't hardcode the classname in the format, so that we get the
1002
correct value if the method is inherited by a subclass. If you're
1003
printing attributes of the object, including strings, you should normally
1004
use ``%r`` syntax (to call their repr in turn).
1006
Try to avoid the representation becoming more than one or two lines long.
1007
(But balance this against including useful information, and simplicity of
1010
Because repr methods are often called when something has already gone
1011
wrong, they should be written somewhat more defensively than most code.
1012
The object may be half-initialized or in some other way in an illegal
1013
state. The repr method shouldn't raise an exception, or it may hide the
1014
(probably more useful) underlying exception.
1019
return '%s(%r)' % (self.__class__.__name__,
1026
A bare ``except`` statement will catch all exceptions, including ones that
1027
really should terminate the program such as ``MemoryError`` and
1028
``KeyboardInterrupt``. They should rarely be used unless the exception is
1029
later re-raised. Even then, think about whether catching just
1030
``Exception`` (which excludes system errors in Python2.5 and later) would
1041
We have a commitment to 6 months API stability - any supported symbol in a
1042
release of bzr MUST NOT be altered in any way that would result in
1043
breaking existing code that uses it. That means that method names,
1044
parameter ordering, parameter names, variable and attribute names etc must
1045
not be changed without leaving a 'deprecated forwarder' behind. This even
1046
applies to modules and classes.
1048
If you wish to change the behaviour of a supported API in an incompatible
1049
way, you need to change its name as well. For instance, if I add an optional keyword
1050
parameter to branch.commit - that's fine. On the other hand, if I add a
1051
keyword parameter to branch.commit which is a *required* transaction
1052
object, I should rename the API - i.e. to 'branch.commit_transaction'.
1054
When renaming such supported API's, be sure to leave a deprecated_method (or
1055
_function or ...) behind which forwards to the new API. See the
1056
bzrlib.symbol_versioning module for decorators that take care of the
1057
details for you - such as updating the docstring, and issuing a warning
1058
when the old api is used.
1060
For unsupported API's, it does not hurt to follow this discipline, but it's
1061
not required. Minimally though, please try to rename things so that
1062
callers will at least get an AttributeError rather than weird results.
1065
Deprecation decorators
1066
----------------------
1068
``bzrlib.symbol_versioning`` provides decorators that can be attached to
1069
methods, functions, and other interfaces to indicate that they should no
1070
longer be used. For example::
1072
@deprecated_method(deprecated_in((0, 1, 4)))
1074
return self._new_foo()
1076
To deprecate a static method you must call ``deprecated_function``
1077
(**not** method), after the staticmethod call::
1080
@deprecated_function(deprecated_in((0, 1, 4)))
1081
def create_repository(base, shared=False, format=None):
1083
When you deprecate an API, you should not just delete its tests, because
1084
then we might introduce bugs in them. If the API is still present at all,
1085
it should still work. The basic approach is to use
1086
``TestCase.applyDeprecated`` which in one step checks that the API gives
1087
the expected deprecation message, and also returns the real result from
1088
the method, so that tests can keep running.
1090
Deprecation warnings will be suppressed for final releases, but not for
1091
development versions or release candidates, or when running ``bzr
1092
selftest``. This gives developers information about whether their code is
1093
using deprecated functions, but avoids confusing users about things they
1100
Processing Command Lines
1101
------------------------
1103
bzrlib has a standard framework for parsing command lines and calling
1104
processing routines associated with various commands. See builtins.py
1105
for numerous examples.
1108
Standard Parameter Types
1109
------------------------
1111
There are some common requirements in the library: some parameters need to be
1112
unicode safe, some need byte strings, and so on. At the moment we have
1113
only codified one specific pattern: Parameters that need to be unicode
1114
should be checked via ``bzrlib.osutils.safe_unicode``. This will coerce the
1115
input into unicode in a consistent fashion, allowing trivial strings to be
1116
used for programmer convenience, but not performing unpredictably in the
1117
presence of different locales.
1123
(The strategy described here is what we want to get to, but it's not
1124
consistently followed in the code at the moment.)
1126
bzrlib is intended to be a generically reusable library. It shouldn't
1127
write messages to stdout or stderr, because some programs that use it
1128
might want to display that information through a GUI or some other
1131
We can distinguish two types of output from the library:
1133
1. Structured data representing the progress or result of an
1134
operation. For example, for a commit command this will be a list
1135
of the modified files and the finally committed revision number
1138
These should be exposed either through the return code or by calls
1139
to a callback parameter.
1141
A special case of this is progress indicators for long-lived
1142
operations, where the caller should pass a ProgressBar object.
1144
2. Unstructured log/debug messages, mostly for the benefit of the
1145
developers or users trying to debug problems. This should always
1146
be sent through ``bzrlib.trace`` and Python ``logging``, so that
1147
it can be redirected by the client.
1149
The distinction between the two is a bit subjective, but in general if
1150
there is any chance that a library would want to see something as
1151
structured data, we should make it so.
1153
The policy about how output is presented in the text-mode client
1154
should be only in the command-line tool.
1161
Bazaar has online help for various topics through ``bzr help COMMAND`` or
1162
equivalently ``bzr command -h``. We also have help on command options,
1163
and on other help topics. (See ``help_topics.py``.)
1165
As for python docstrings, the first paragraph should be a single-sentence
1166
synopsis of the command.
1168
The help for options should be one or more proper sentences, starting with
1169
a capital letter and finishing with a full stop (period).
1171
All help messages and documentation should have two spaces between
1178
In general tests should be placed in a file named test_FOO.py where
1179
FOO is the logical thing under test. That file should be placed in the
1180
tests subdirectory under the package being tested.
1182
For example, tests for merge3 in bzrlib belong in bzrlib/tests/test_merge3.py.
1183
See bzrlib/tests/test_sampler.py for a template test script.
1185
Tests can be written for the UI or for individual areas of the library.
1186
Choose whichever is appropriate: if adding a new command, or a new command
1187
option, then you should be writing a UI test. If you are both adding UI
1188
functionality and library functionality, you will want to write tests for
1189
both the UI and the core behaviours. We call UI tests 'blackbox' tests
1190
and they are found in ``bzrlib/tests/blackbox/*.py``.
1192
When writing blackbox tests please honour the following conventions:
1194
1. Place the tests for the command 'name' in
1195
bzrlib/tests/blackbox/test_name.py. This makes it easy for developers
1196
to locate the test script for a faulty command.
1198
2. Use the 'self.run_bzr("name")' utility function to invoke the command
1199
rather than running bzr in a subprocess or invoking the
1200
cmd_object.run() method directly. This is a lot faster than
1201
subprocesses and generates the same logging output as running it in a
1202
subprocess (which invoking the method directly does not).
1204
3. Only test the one command in a single test script. Use the bzrlib
1205
library when setting up tests and when evaluating the side-effects of
1206
the command. We do this so that the library api has continual pressure
1207
on it to be as functional as the command line in a simple manner, and
1208
to isolate knock-on effects throughout the blackbox test suite when a
1209
command changes its name or signature. Ideally only the tests for a
1210
given command are affected when a given command is changed.
1212
4. If you have a test which does actually require running bzr in a
1213
subprocess you can use ``run_bzr_subprocess``. By default the spawned
1214
process will not load plugins unless ``--allow-plugins`` is supplied.
1220
We have a rich collection of tools to support writing tests. Please use
1221
them in preference to ad-hoc solutions as they provide portability and
1222
performance benefits.
1227
The ``TreeBuilder`` interface allows the construction of arbitrary trees
1228
with a declarative interface. A sample session might look like::
1230
tree = self.make_branch_and_tree('path')
1231
builder = TreeBuilder()
1232
builder.start_tree(tree)
1233
builder.build(['foo', "bar/", "bar/file"])
1234
tree.commit('commit the tree')
1235
builder.finish_tree()
1237
Please see bzrlib.treebuilder for more details.
1242
The ``BranchBuilder`` interface allows the creation of test branches in a
1243
quick and easy manner. A sample session::
1245
builder = BranchBuilder(self.get_transport().clone('relpath'))
1246
builder.build_commit()
1247
builder.build_commit()
1248
builder.build_commit()
1249
branch = builder.get_branch()
1251
Please see bzrlib.branchbuilder for more details.
1256
We make selective use of doctests__. In general they should provide
1257
*examples* within the API documentation which can incidentally be tested. We
1258
don't try to test every important case using doctests -- regular Python
1259
tests are generally a better solution.
1261
Most of these are in ``bzrlib/doc/api``. More additions are welcome.
1263
__ http://docs.python.org/lib/module-doctest.html
1268
Currently, bzr selftest is used to invoke tests.
1269
You can provide a pattern argument to run a subset. For example,
1270
to run just the blackbox tests, run::
1272
./bzr selftest -v blackbox
1274
To skip a particular test (or set of tests), use the --exclude option
1275
(shorthand -x) like so::
1277
./bzr selftest -v -x blackbox
1279
To list tests without running them, use the --list-only option like so::
1281
./bzr selftest --list-only
1283
This option can be combined with other selftest options (like -x) and
1284
filter patterns to understand their effect.
1287
Handling Errors and Exceptions
1288
==============================
1290
Commands should return non-zero when they encounter circumstances that
1291
the user should really pay attention to - which includes trivial shell
1294
Recommended values are:
1297
1. Conflicts in merge-like operations, or changes are present in
1298
diff-like operations.
1299
2. Unrepresentable diff changes (i.e. binary files that we cannot show
1301
3. An error or exception has occurred.
1302
4. An internal error occurred (one that shows a traceback.)
1304
Errors are handled through Python exceptions. Exceptions should be defined
1305
inside bzrlib.errors, so that we can see the whole tree at a glance.
1307
We broadly classify errors as either being either internal or not,
1308
depending on whether ``internal_error`` is set or not. If we think it's our
1309
fault, we show a backtrace, an invitation to report the bug, and possibly
1310
other details. This is the default for errors that aren't specifically
1311
recognized as being caused by a user error. Otherwise we show a briefer
1312
message, unless -Derror was given.
1314
Many errors originate as "environmental errors" which are raised by Python
1315
or builtin libraries -- for example IOError. These are treated as being
1316
our fault, unless they're caught in a particular tight scope where we know
1317
that they indicate a user errors. For example if the repository format
1318
is not found, the user probably gave the wrong path or URL. But if one of
1319
the files inside the repository is not found, then it's our fault --
1320
either there's a bug in bzr, or something complicated has gone wrong in
1321
the environment that means one internal file was deleted.
1323
Many errors are defined in ``bzrlib/errors.py`` but it's OK for new errors
1324
to be added near the place where they are used.
1326
Exceptions are formatted for the user by conversion to a string
1327
(eventually calling their ``__str__`` method.) As a convenience the
1328
``._fmt`` member can be used as a template which will be mapped to the
1329
error's instance dict.
1331
New exception classes should be defined when callers might want to catch
1332
that exception specifically, or when it needs a substantially different
1335
Exception strings should start with a capital letter and should not have a
1336
final fullstop. If long, they may contain newlines to break the text.
1342
Do not use the Python ``assert`` statement, either in tests or elsewhere.
1343
A source test checks that it is not used. It is ok to explicitly raise
1348
* It makes the behaviour vary depending on whether bzr is run with -O
1349
or not, therefore giving a chance for bugs that occur in one case or
1350
the other, several of which have already occurred: assertions with
1351
side effects, code which can't continue unless the assertion passes,
1352
cases where we should give the user a proper message rather than an
1354
* It's not that much shorter than an explicit if/raise.
1355
* It tends to lead to fuzzy thinking about whether the check is
1356
actually needed or not, and whether it's an internal error or not
1357
* It tends to cause look-before-you-leap patterns.
1358
* It's unsafe if the check is needed to protect the integrity of the
1360
* It tends to give poor messages since the developer can get by with
1361
no explanatory text at all.
1362
* We can't rely on people always running with -O in normal use, so we
1363
can't use it for tests that are actually expensive.
1364
* Expensive checks that help developers are better turned on from the
1365
test suite or a -D flag.
1366
* If used instead of ``self.assert*()`` in tests it makes them falsely pass with -O.
1372
When you change bzrlib, please update the relevant documentation for the
1373
change you made: Changes to commands should update their help, and
1374
possibly end user tutorials; changes to the core library should be
1375
reflected in API documentation.
1380
If you make a user-visible change, please add a note to the NEWS file.
1381
The description should be written to make sense to someone who's just
1382
a user of bzr, not a developer: new functions or classes shouldn't be
1383
mentioned, but new commands, changes in behaviour or fixed nontrivial
1384
bugs should be listed. See the existing entries for an idea of what
1387
Within each release, entries in the news file should have the most
1388
user-visible changes first. So the order should be approximately:
1390
* changes to existing behaviour - the highest priority because the
1391
user's existing knowledge is incorrect
1392
* new features - should be brought to their attention
1393
* bug fixes - may be of interest if the bug was affecting them, and
1394
should include the bug number if any
1395
* major documentation changes
1396
* changes to internal interfaces
1398
People who made significant contributions to each change are listed in
1399
parenthesis. This can include reporting bugs (particularly with good
1400
details or reproduction recipes), submitting patches, etc.
1405
The docstring of a command is used by ``bzr help`` to generate help output
1406
for the command. The list 'takes_options' attribute on a command is used by
1407
``bzr help`` to document the options for the command - the command
1408
docstring does not need to document them. Finally, the '_see_also'
1409
attribute on a command can be used to reference other related help topics.
1414
Functions, methods, classes and modules should have docstrings
1415
describing how they are used.
1417
The first line of the docstring should be a self-contained sentence.
1419
For the special case of Command classes, this acts as the user-visible
1420
documentation shown by the help command.
1422
The docstrings should be formatted as reStructuredText_ (like this
1423
document), suitable for processing using the epydoc_ tool into HTML
1426
.. _reStructuredText: http://docutils.sourceforge.net/rst.html
1427
.. _epydoc: http://epydoc.sourceforge.net/
1436
The copyright policy for bzr was recently made clear in this email (edited
1437
for grammatical correctness)::
1439
The attached patch cleans up the copyright and license statements in
1440
the bzr source. It also adds tests to help us remember to add them
1441
with the correct text.
1443
We had the problem that lots of our files were "Copyright Canonical
1444
Development Ltd" which is not a real company, and some other variations
1445
on this theme. Also, some files were missing the GPL statements.
1447
I want to be clear about the intent of this patch, since copyright can
1448
be a little controversial.
1450
1) The big motivation for this is not to shut out the community, but
1451
just to clean up all of the invalid copyright statements.
1453
2) It has been the general policy for bzr that we want a single
1454
copyright holder for all of the core code. This is following the model
1455
set by the FSF, which makes it easier to update the code to a new
1456
license in case problems are encountered. (For example, if we want to
1457
upgrade the project universally to GPL v3 it is much simpler if there is
1458
a single copyright holder). It also makes it clearer if copyright is
1459
ever debated, there is a single holder, which makes it easier to defend
1460
in court, etc. (I think the FSF position is that if you assign them
1461
copyright, they can defend it in court rather than you needing to, and
1462
I'm sure Canonical would do the same).
1463
As such, Canonical has requested copyright assignments from all of the
1466
3) If someone wants to add code and not attribute it to Canonical, there
1467
is a specific list of files that are excluded from this check. And the
1468
test failure indicates where that is, and how to update it.
1470
4) If anyone feels that I changed a copyright statement incorrectly, just
1471
let me know, and I'll be happy to correct it. Whenever you have large
1472
mechanical changes like this, it is possible to make some mistakes.
1474
Just to reiterate, this is a community project, and it is meant to stay
1475
that way. Core bzr code is copyright Canonical for legal reasons, and
1476
the tests are just there to help us maintain that.
1479
Miscellaneous Topics
1480
####################
1485
Bazaar has a few facilities to help debug problems by going into pdb_, the
1488
.. _pdb: http://docs.python.org/lib/debugger-commands.html
1490
If the ``BZR_PDB`` environment variable is set
1491
then bzr will go into pdb post-mortem mode when an unhandled exception
1494
If you send a SIGQUIT signal to bzr, which can be done by pressing
1495
Ctrl-\\ on Unix, bzr will go into the debugger immediately. You can
1496
continue execution by typing ``c``. This can be disabled if necessary
1497
by setting the environment variable ``BZR_SIGQUIT_PDB=0``.
1504
Integer identifier for a revision on the main line of a branch.
1505
Revision 0 is always the null revision; others are 1-based
1506
indexes into the branch's revision history.
1509
Unicode and Encoding Support
1510
============================
1512
This section discusses various techniques that Bazaar uses to handle
1513
characters that are outside the ASCII set.
1518
When a ``Command`` object is created, it is given a member variable
1519
accessible by ``self.outf``. This is a file-like object, which is bound to
1520
``sys.stdout``, and should be used to write information to the screen,
1521
rather than directly writing to ``sys.stdout`` or calling ``print``.
1522
This file has the ability to translate Unicode objects into the correct
1523
representation, based on the console encoding. Also, the class attribute
1524
``encoding_type`` will effect how unprintable characters will be
1525
handled. This parameter can take one of 3 values:
1528
Unprintable characters will be represented with a suitable replacement
1529
marker (typically '?'), and no exception will be raised. This is for
1530
any command which generates text for the user to review, rather than
1531
for automated processing.
1532
For example: ``bzr log`` should not fail if one of the entries has text
1533
that cannot be displayed.
1536
Attempting to print an unprintable character will cause a UnicodeError.
1537
This is for commands that are intended more as scripting support, rather
1538
than plain user review.
1539
For exampl: ``bzr ls`` is designed to be used with shell scripting. One
1540
use would be ``bzr ls --null --unknows | xargs -0 rm``. If ``bzr``
1541
printed a filename with a '?', the wrong file could be deleted. (At the
1542
very least, the correct file would not be deleted). An error is used to
1543
indicate that the requested action could not be performed.
1546
Do not attempt to automatically convert Unicode strings. This is used
1547
for commands that must handle conversion themselves.
1548
For example: ``bzr diff`` needs to translate Unicode paths, but should
1549
not change the exact text of the contents of the files.
1552
``bzrlib.urlutils.unescape_for_display``
1553
----------------------------------------
1555
Because Transports work in URLs (as defined earlier), printing the raw URL
1556
to the user is usually less than optimal. Characters outside the standard
1557
set are printed as escapes, rather than the real character, and local
1558
paths would be printed as ``file://`` urls. The function
1559
``unescape_for_display`` attempts to unescape a URL, such that anything
1560
that cannot be printed in the current encoding stays an escaped URL, but
1561
valid characters are generated where possible.
1567
The ``bzrlib.osutils`` module has many useful helper functions, including
1568
some more portable variants of functions in the standard library.
1570
In particular, don't use ``shutil.rmtree`` unless it's acceptable for it
1571
to fail on Windows if some files are readonly or still open elsewhere.
1572
Use ``bzrlib.osutils.rmtree`` instead.
1578
We write some extensions in C using pyrex. We design these to work in
1581
* User with no C compiler
1582
* User with C compiler
1585
The recommended way to install bzr is to have a C compiler so that the
1586
extensions can be built, but if no C compiler is present, the pure python
1587
versions we supply will work, though more slowly.
1589
For developers we recommend that pyrex be installed, so that the C
1590
extensions can be changed if needed.
1592
For the C extensions, the extension module should always match the
1593
original python one in all respects (modulo speed). This should be
1594
maintained over time.
1596
To create an extension, add rules to setup.py for building it with pyrex,
1597
and with distutils. Now start with an empty .pyx file. At the top add
1598
"include 'yourmodule.py'". This will import the contents of foo.py into this
1599
file at build time - remember that only one module will be loaded at
1600
runtime. Now you can subclass classes, or replace functions, and only your
1601
changes need to be present in the .pyx file.
1603
Note that pyrex does not support all 2.4 programming idioms, so some
1604
syntax changes may be required. I.e.
1606
- 'from foo import (bar, gam)' needs to change to not use the brackets.
1607
- 'import foo.bar as bar' needs to be 'import foo.bar; bar = foo.bar'
1609
If the changes are too dramatic, consider
1610
maintaining the python code twice - once in the .pyx, and once in the .py,
1611
and no longer including the .py file.
1614
Making Installers for OS Windows
1615
================================
1616
To build a win32 installer, see the instructions on the wiki page:
1617
http://bazaar-vcs.org/BzrWin32Installer
1620
Core Developer Tasks
1621
####################
1626
What is a Core Developer?
1627
-------------------------
1629
While everyone in the Bazaar community is welcome and encouraged to
1630
propose and submit changes, a smaller team is reponsible for pulling those
1631
changes together into a cohesive whole. In addition to the general developer
1632
stuff covered above, "core" developers have responsibility for:
1635
* reviewing blueprints
1637
* managing releases (see the `Releasing Bazaar <../../developers/releasing.html>`_)
1640
Removing barriers to community participation is a key reason for adopting
1641
distributed VCS technology. While DVCS removes many technical barriers,
1642
a small number of social barriers are often necessary instead.
1643
By documenting how the above things are done, we hope to
1644
encourage more people to participate in these activities, keeping the
1645
differences between core and non-core contributors to a minimum.
1648
Communicating and Coordinating
1649
------------------------------
1651
While it has many advantages, one of the challenges of distributed
1652
development is keeping everyone else aware of what you're working on.
1653
There are numerous ways to do this:
1655
#. Assign bugs to yourself in Launchpad
1656
#. Mention it on the mailing list
1657
#. Mention it on IRC
1659
As well as the email notifcations that occur when merge requests are sent
1660
and reviewed, you can keep others informed of where you're spending your
1661
energy by emailing the **bazaar-commits** list implicitly. To do this,
1662
install and configure the Email plugin. One way to do this is add these
1663
configuration settings to your central configuration file (e.g.
1664
``~/.bazaar/bazaar.conf`` on Linux)::
1667
email = Joe Smith <joe.smith@internode.on.net>
1668
smtp_server = mail.internode.on.net:25
1670
Then add these lines for the relevant branches in ``locations.conf``::
1672
post_commit_to = bazaar-commits@lists.canonical.com
1673
post_commit_mailer = smtplib
1675
While attending a sprint, RobertCollins' Dbus plugin is useful for the
1676
same reason. See the documentation within the plugin for information on
1677
how to set it up and configure it.
1683
Setting Up Your Workspace for Reviews
1684
-------------------------------------
1686
TODO: Incorporate John Arbash Meinel's detailed email to Ian C on the
1687
numerous ways of setting up integration branches.
1690
The Review Checklist
1691
--------------------
1693
See `A Closer Look at the Merge & Review Process`_
1694
for information on the gates used to decide whether code can be merged
1695
or not and details on how review results are recorded and communicated.
1698
The Importance of Timely Reviews
1699
--------------------------------
1701
Good reviews do take time. They also regularly require a solid
1702
understanding of the overall code base. In practice, this means a small
1703
number of people often have a large review burden - with knowledge comes
1704
responsibility. No one like their merge requests sitting in a queue going
1705
nowhere, so reviewing sooner rather than later is strongly encouraged.
1714
Of the many workflows supported by Bazaar, the one adopted for Bazaar
1715
development itself is known as "Decentralized with automatic gatekeeper".
1716
To repeat the explanation of this given on
1717
http://bazaar-vcs.org/Workflows:
1720
In this workflow, each developer has their own branch or
1721
branches, plus read-only access to the mainline. A software gatekeeper
1722
(e.g. PQM) has commit rights to the main branch. When a developer wants
1723
their work merged, they request the gatekeeper to merge it. The gatekeeper
1724
does a merge, a compile, and runs the test suite. If the code passes, it
1725
is merged into the mainline.
1727
In a nutshell, here's the overall submission process:
1729
#. get your work ready (including review except for trivial changes)
1730
#. push to a public location
1731
#. ask PQM to merge from that location
1734
At present, PQM always takes the changes to merge from a branch
1735
at a URL that can be read by it. For Bazaar, that means a public,
1736
typically http, URL.
1738
As a result, the following things are needed to use PQM for submissions:
1740
#. A publicly available web server
1741
#. Your OpenPGP key registered with PQM (contact RobertCollins for this)
1742
#. The PQM plugin installed and configured (not strictly required but
1743
highly recommended).
1746
Selecting a Public Branch Location
1747
----------------------------------
1749
If you don't have your own web server running, branches can always be
1750
pushed to Launchpad. Here's the process for doing that:
1752
Depending on your location throughout the world and the size of your
1753
repository though, it is often quicker to use an alternative public
1754
location to Launchpad, particularly if you can set up your own repo and
1755
push into that. By using an existing repo, push only needs to send the
1756
changes, instead of the complete repository every time. Note that it is
1757
easy to register branches in other locations with Launchpad so no benefits
1758
are lost by going this way.
1761
For Canonical staff, http://people.ubuntu.com/~<user>/ is one
1762
suggestion for public http branches. Contact your manager for information
1763
on accessing this system if required.
1765
It should also be noted that best practice in this area is subject to
1766
change as things evolve. For example, once the Bazaar smart server on
1767
Launchpad supports server-side branching, the performance situation will
1768
be very different to what it is now (Jun 2007).
1771
Configuring the PQM Plug-In
1772
---------------------------
1774
While not strictly required, the PQM plugin automates a few things and
1775
reduces the chance of error. Before looking at the plugin, it helps to
1776
understand a little more how PQM operates. Basically, PQM requires an
1777
email indicating what you want it to do. The email typically looks like
1780
star-merge source-branch target-branch
1784
star-merge http://bzr.arbash-meinel.com/branches/bzr/jam-integration http://bazaar-vcs.org/bzr/bzr.dev
1786
Note that the command needs to be on one line. The subject of the email
1787
will be used for the commit message. The email also needs to be ``gpg``
1788
signed with a key that PQM accepts.
1790
The advantages of using the PQM plugin are:
1792
#. You can use the config policies to make it easy to set up public
1793
branches, so you don't have to ever type the full paths you want to merge
1796
#. It checks to make sure the public branch last revision matches the
1797
local last revision so you are submitting what you think you are.
1799
#. It uses the same public_branch and smtp sending settings as bzr-email,
1800
so if you have one set up, you have the other mostly set up.
1802
#. Thunderbird refuses to not wrap lines, and request lines are usually
1803
pretty long (you have 2 long URLs in there).
1805
Here are sample configuration settings for the PQM plugin. Here are the
1806
lines in bazaar.conf::
1809
email = Joe Smith <joe.smith@internode.on.net>
1810
smtp_server=mail.internode.on.net:25
1812
And here are the lines in ``locations.conf`` (or ``branch.conf`` for
1813
dirstate-tags branches)::
1815
[/home/joe/bzr/my-integration]
1816
push_location = sftp://joe-smith@bazaar.launchpad.net/%7Ejoe-smith/bzr/my-integration/
1817
push_location:policy = norecurse
1818
public_branch = http://bazaar.launchpad.net/~joe-smith/bzr/my-integration/
1819
public_branch:policy = appendpath
1820
pqm_email = Bazaar PQM <pqm@bazaar-vcs.org>
1821
pqm_branch = http://bazaar-vcs.org/bzr/bzr.dev
1823
Note that the push settings will be added by the first ``push`` on
1824
a branch. Indeed the preferred way to generate the lines above is to use
1825
``push`` with an argument, then copy-and-paste the other lines into
1832
Here is one possible recipe once the above environment is set up:
1834
#. pull bzr.dev => my-integration
1835
#. merge patch => my-integration
1836
#. fix up any final merge conflicts (NEWS being the big killer here).
1842
The ``push`` step is not required if ``my-integration`` is a checkout of
1845
Because of defaults, you can type a single message into commit and
1846
pqm-commit will reuse that.
1849
Tracking Change Acceptance
1850
--------------------------
1852
The web interface to PQM is https://pqm.bazaar-vcs.org/. After submitting
1853
a change, you can visit this URL to confirm it was received and placed in
1856
When PQM completes processing a change, an email is sent to you with the
1860
Reviewing Blueprints
1861
====================
1863
Blueprint Tracking Using Launchpad
1864
----------------------------------
1866
New features typically require a fair amount of discussion, design and
1867
debate. For Bazaar, that information is often captured in a so-called
1868
"blueprint" on our Wiki. Overall tracking of blueprints and their status
1869
is done using Launchpad's relevant tracker,
1870
https://blueprints.launchpad.net/bzr/. Once a blueprint for ready for
1871
review, please announce it on the mailing list.
1873
Alternatively, send an email begining with [RFC] with the proposal to the
1874
list. In some cases, you may wish to attach proposed code or a proposed
1875
developer document if that best communicates the idea. Debate can then
1876
proceed using the normal merge review processes.
1879
Recording Blueprint Review Feedback
1880
-----------------------------------
1882
Unlike its Bug Tracker, Launchpad's Blueprint Tracker doesn't currently
1883
(Jun 2007) support a chronological list of comment responses. Review
1884
feedback can either be recorded on the Wiki hosting the blueprints or by
1885
using Launchpad's whiteboard feature.
1894
As the two senior developers, Martin Pool and Robert Collins coordinate
1895
the overall Bazaar product development roadmap. Core developers provide
1896
input and review into this, particularly during sprints. It's totally
1897
expected that community members ought to be working on things that
1898
interest them the most. The roadmap is valuable though because it provides
1899
context for understanding where the product is going as a whole and why.
1902
Using Releases and Milestones in Launchpad
1903
------------------------------------------
1905
TODO ... (Exact policies still under discussion)
1911
Keeping on top of bugs reported is an important part of ongoing release
1912
planning. Everyone in the community is welcome and encouraged to raise
1913
bugs, confirm bugs raised by others, and nominate a priority. Practically
1914
though, a good percentage of bug triage is often done by the core
1915
developers, partially because of their depth of product knowledge.
1917
With respect to bug triage, core developers are encouraged to play an
1918
active role with particular attention to the following tasks:
1920
* keeping the number of unconfirmed bugs low
1921
* ensuring the priorities are generally right (everything as critical - or
1922
medium - is meaningless)
1923
* looking out for regressions and turning those around sooner rather than later.
1926
As well as prioritizing bugs and nominating them against a
1927
target milestone, Launchpad lets core developers offer to mentor others in
1932
vim: ft=rst tw=74 ai
added
removed
doc/developers/HACKING.txt
