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 latest developer documentation can be found online at
15
http://doc.bazaar.canonical.com/developers/.
20
Exploring the Bazaar Platform
21
=============================
23
Before making changes, it's a good idea to explore the work already
24
done by others. Perhaps the new feature or improvement you're looking
25
for is available in another plug-in already? If you find a bug,
26
perhaps someone else has already fixed it?
28
To answer these questions and more, take a moment to explore the
29
overall Bazaar Platform. Here are some links to browse:
31
* The Plugins page on the Wiki - http://wiki.bazaar.canonical.com/BzrPlugins
33
* The Bazaar product family on Launchpad - https://launchpad.net/bazaar
35
* Bug Tracker for the core product - https://bugs.launchpad.net/bzr/
37
If nothing else, perhaps you'll find inspiration in how other developers
38
have solved their challenges.
40
Finding Something To Do
41
=======================
43
Ad-hoc performance work can also be done. One useful tool is the 'evil' debug
44
flag. For instance running ``bzr -Devil commit -m "test"`` will log a backtrace
45
to the bzr log file for every method call which triggers a slow or non-scalable
46
part of the bzr library. So checking that a given command with ``-Devil`` has
47
no backtraces logged to the log file is a good way to find problem function
48
calls that might be nested deep in the code base.
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://wiki.bazaar.canonical.com/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 of 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
.. was from bazaar-vcs.org/BzrGivingBack
78
One of the fun things about working on a version control system like Bazaar is
79
that the users have a high level of proficiency in contributing back into
80
the tool. Consider the following very brief introduction to contributing back
81
to Bazaar. More detailed instructions are in the following sections.
86
First, get a local copy of the development mainline (See `Why make a local
92
$ bzr branch http://bazaar-vcs.org/bzr/bzr.dev/ bzr.dev
94
Now make your own branch::
96
$ bzr branch bzr.dev 123456-my-bugfix
98
This will give you a branch called "123456-my-bugfix" that you can work on
99
and commit in. Here, you can study the code, make a fix or a new feature.
100
Feel free to commit early and often (after all, it's your branch!).
102
Documentation improvements are an easy place to get started giving back to the
103
Bazaar project. The documentation is in the `doc/` subdirectory of the Bazaar
106
When you are done, make sure that you commit your last set of changes as well!
107
Once you are happy with your changes, ask for them to be merged, as described
110
Making a Merge Proposal
111
-----------------------
113
The Bazaar developers use Launchpad to further enable a truly distributed
114
style of development. Anyone can propose a branch for merging into the Bazaar
115
trunk. To start this process, you need to push your branch to Launchpad. To
116
do this, you will need a Launchpad account and user name, e.g.
117
`your_lp_username`. You can push your branch to Launchpad directly from
120
$ bzr push lp:~your_lp_username/bzr/meaningful_name_here
122
After you have pushed your branch, you will need to propose it for merging to
123
the Bazaar trunk. Go to
124
<https://launchpad.net/your_lp_username/bzr/meaningful_name_here> and choose
125
"Propose for merging into another branch". Select "~bzr/bzr/trunk" to hand
126
your changes off to the Bazaar developers for review and merging.
128
Alternatively, after pushing you can use the ``lp-propose`` command to
129
create the merge proposal.
131
Using a meaningful name for your branch will help you and the reviewer(s)
132
better track the submission. Use a very succint description of your submission
133
and prefix it with bug number if needed (lp:~mbp/bzr/484558-merge-directory
134
for example). Alternatively, you can suffix with the bug number
135
(lp:~jameinel/bzr/export-file-511987).
141
Please put a "cover letter" on your merge request explaining:
143
* the reason **why** you're making this change
145
* **how** this change achieves this purpose
147
* anything else you may have fixed in passing
149
* anything significant that you thought of doing, such as a more
150
extensive fix or a different approach, but didn't or couldn't do now
152
A good cover letter makes reviewers' lives easier because they can decide
153
from the letter whether they agree with the purpose and approach, and then
154
assess whether the patch actually does what the cover letter says.
155
Explaining any "drive-by fixes" or roads not taken may also avoid queries
156
from the reviewer. All in all this should give faster and better reviews.
157
Sometimes writing the cover letter helps the submitter realize something
158
else they need to do. The size of the cover letter should be proportional
159
to the size and complexity of the patch.
162
Why make a local copy of bzr.dev?
163
---------------------------------
165
Making a local mirror of bzr.dev is not strictly necessary, but it means
167
- You can use that copy of bzr.dev as your main bzr executable, and keep it
168
up-to-date using ``bzr pull``.
169
- Certain operations are faster, and can be done when offline. For example:
172
- ``bzr diff -r ancestor:...``
175
- When it's time to create your next branch, it's more convenient. When you
176
have further contributions to make, you should do them in their own branch::
179
$ bzr branch bzr.dev additional_fixes
180
$ cd additional_fixes # hack, hack, hack
184
Understanding the Development Process
185
=====================================
187
The development team follows many practices including:
189
* a public roadmap and planning process in which anyone can participate
191
* time based milestones everyone can work towards and plan around
193
* extensive code review and feedback to contributors
195
* complete and rigorous test coverage on any code contributed
197
* automated validation that all tests still pass before code is merged
198
into the main code branch.
200
The key tools we use to enable these practices are:
202
* Launchpad - https://launchpad.net/
204
* Bazaar - http://bazaar.canonical.com/
206
* Patch Queue Manager - https://launchpad.net/pqm/
208
For further information, see <http://wiki.bazaar.canonical.com/BzrDevelopment>.
213
Preparing a Sandbox for Making Changes to Bazaar
214
================================================
216
Bazaar supports many ways of organising your work. See
217
http://wiki.bazaar.canonical.com/SharedRepositoryLayouts for a summary of the
218
popular alternatives.
220
Of course, the best choice for you will depend on numerous factors:
221
the number of changes you may be making, the complexity of the changes, etc.
222
As a starting suggestion though:
224
* create a local copy of the main development branch (bzr.dev) by using
227
bzr branch http://bazaar-vcs.org/bzr/bzr.dev/ bzr.dev
229
* keep your copy of bzr.dev pristine (by not developing in it) and keep
230
it up to date (by using bzr pull)
232
* create a new branch off your local bzr.dev copy for each issue
233
(bug or feature) you are working on.
235
This approach makes it easy to go back and make any required changes
236
after a code review. Resubmitting the change is then simple with no
237
risk of accidentally including edits related to other issues you may
238
be working on. After the changes for an issue are accepted and merged,
239
the associated branch can be deleted or archived as you wish.
242
Navigating the Code Base
243
========================
245
.. Was at <http://bazaar-vcs.org/NewDeveloperIntroduction>
247
Some of the key files in this directory are:
250
The command you run to start Bazaar itself. This script is pretty
251
short and just does some checks then jumps into bzrlib.
254
This file covers a brief introduction to Bazaar and lists some of its
258
Summary of changes in each Bazaar release that can affect users or
262
Installs Bazaar system-wide or to your home directory. To perform
263
development work on Bazaar it is not required to run this file - you
264
can simply run the bzr command from the top level directory of your
265
development copy. Note: That if you run setup.py this will create a
266
'build' directory in your development branch. There's nothing wrong
267
with this but don't be confused by it. The build process puts a copy
268
of the main code base into this build directory, along with some other
269
files. You don't need to go in here for anything discussed in this
273
Possibly the most exciting folder of all, bzrlib holds the main code
274
base. This is where you will go to edit python files and contribute to
278
Holds documentation on a whole range of things on Bazaar from the
279
origination of ideas within the project to information on Bazaar
280
features and use cases. Within this directory there is a subdirectory
281
for each translation into a human language. All the documentation
282
is in the ReStructuredText markup language.
285
Documentation specifically targeted at Bazaar and plugin developers.
286
(Including this document.)
290
Automatically-generated API reference information is available at
291
<http://starship.python.net/crew/mwh/bzrlibapi/>.
293
See also the `Bazaar Architectural Overview
294
<http://doc.bazaar.canonical.com/developers/overview.html>`_.
303
We don't change APIs in stable branches: any supported symbol in a stable
304
release of bzr must not be altered in any way that would result in
1
============================
2
Guidelines for modifying bzr
3
============================
7
(The current version of this document is available in the file ``HACKING``
8
in the source tree, or at http://doc.bazaar-vcs.org/current/hacking.html)
13
* New functionality should have test cases. Preferably write the
14
test before writing the code.
16
In general, you can test at either the command-line level or the
17
internal API level. See Writing Tests below for more detail.
19
* Try to practice Test-Driven Development. before fixing a bug, write a
20
test case so that it does not regress. Similarly for adding a new
21
feature: write a test case for a small version of the new feature before
22
starting on the code itself. Check the test fails on the old code, then
23
add the feature or fix and check it passes.
25
* Exceptions should be defined inside bzrlib.errors, so that we can
26
see the whole tree at a glance.
28
* Imports should be done at the top-level of the file, unless there is
29
a strong reason to have them lazily loaded when a particular
30
function runs. Import statements have a cost, so try to make sure
31
they don't run inside hot functions.
33
* Module names should always be given fully-qualified,
34
i.e. ``bzrlib.hashcache`` not just ``hashcache``.
36
* Commands should return non-zero when they encounter circumstances that
37
the user should really pay attention to - which includes trivial shell
40
Recommended values are
42
1. Conflicts in merge-like operations, or changes are present in
44
2. Unrepresentable diff changes (i.e. binary files that we cannot show
46
3. An error or exception has occurred.
51
We have a commitment to 6 months API stability - any supported symbol in a
52
release of bzr MUST NOT be altered in any way that would result in
305
53
breaking existing code that uses it. That means that method names,
306
54
parameter ordering, parameter names, variable and attribute names etc must
307
55
not be changed without leaving a 'deprecated forwarder' behind. This even
311
59
way, you need to change its name as well. For instance, if I add an optional keyword
312
60
parameter to branch.commit - that's fine. On the other hand, if I add a
313
61
keyword parameter to branch.commit which is a *required* transaction
314
object, I should rename the API - i.e. to 'branch.commit_transaction'.
316
(Actually, that may break code that provides a new implementation of
317
``commit`` and doesn't expect to receive the parameter.)
62
object, I should rename the API - i.e. to 'branch.commit_transaction'.
319
64
When renaming such supported API's, be sure to leave a deprecated_method (or
320
65
_function or ...) behind which forwards to the new API. See the
321
66
bzrlib.symbol_versioning module for decorators that take care of the
322
67
details for you - such as updating the docstring, and issuing a warning
323
when the old API is used.
68
when the old api is used.
325
70
For unsupported API's, it does not hurt to follow this discipline, but it's
326
71
not required. Minimally though, please try to rename things so that
327
72
callers will at least get an AttributeError rather than weird results.
330
Deprecation decorators
331
----------------------
333
``bzrlib.symbol_versioning`` provides decorators that can be attached to
334
methods, functions, and other interfaces to indicate that they should no
335
longer be used. For example::
337
@deprecated_method(deprecated_in((0, 1, 4)))
339
return self._new_foo()
341
To deprecate a static method you must call ``deprecated_function``
342
(**not** method), after the staticmethod call::
345
@deprecated_function(deprecated_in((0, 1, 4)))
346
def create_repository(base, shared=False, format=None):
348
When you deprecate an API, you should not just delete its tests, because
349
then we might introduce bugs in them. If the API is still present at all,
350
it should still work. The basic approach is to use
351
``TestCase.applyDeprecated`` which in one step checks that the API gives
352
the expected deprecation message, and also returns the real result from
353
the method, so that tests can keep running.
355
Deprecation warnings will be suppressed for final releases, but not for
356
development versions or release candidates, or when running ``bzr
357
selftest``. This gives developers information about whether their code is
358
using deprecated functions, but avoids confusing users about things they
365
Processing Command Lines
366
------------------------
368
bzrlib has a standard framework for parsing command lines and calling
369
processing routines associated with various commands. See builtins.py
370
for numerous examples.
373
Standard Parameter Types
75
Standard parameter types
374
76
------------------------
376
78
There are some common requirements in the library: some parameters need to be
382
84
presence of different locales.
90
The copyright policy for bzr was recently made clear in this email (edited
91
for grammatical correctness)::
93
The attached patch cleans up the copyright and license statements in
94
the bzr source. It also adds tests to help us remember to add them
95
with the correct text.
97
We had the problem that lots of our files were "Copyright Canonical
98
Development Ltd" which is not a real company, and some other variations
99
on this theme. Also, some files were missing the GPL statements.
101
I want to be clear about the intent of this patch, since copyright can
102
be a little controversial.
104
1) The big motivation for this is not to shut out the community, but
105
just to clean up all of the invalid copyright statements.
107
2) It has been the general policy for bzr that we want a single
108
copyright holder for all of the core code. This is following the model
109
set by the FSF, which makes it easier to update the code to a new
110
license in case problems are encountered. (For example, if we want to
111
upgrade the project universally to GPL v3 it is much simpler if there is
112
a single copyright holder). It also makes it clearer if copyright is
113
ever debated, there is a single holder, which makes it easier to defend
114
in court, etc. (I think the FSF position is that if you assign them
115
copyright, they can defend it in court rather than you needing to, and
116
I'm sure Canonical would do the same).
117
As such, Canonical has requested copyright assignments from all of the
120
3) If someone wants to add code and not attribute it to Canonical, there
121
is a specific list of files that are excluded from this check. And the
122
test failure indicates where that is, and how to update it.
124
4) If anyone feels that I changed a copyright statement incorrectly, just
125
let me know, and I'll be happy to correct it. Whenever you have large
126
mechanical changes like this, it is possible to make some mistakes.
128
Just to reiterate, this is a community project, and it is meant to stay
129
that way. Core bzr code is copyright Canonical for legal reasons, and
130
the tests are just there to help us maintain that.
136
If you change the behaviour of a command, please update its docstring
137
in bzrlib/commands.py. This is displayed by the 'bzr help' command.
142
If you make a user-visible change, please add a note to the NEWS file.
143
The description should be written to make sense to someone who's just
144
a user of bzr, not a developer: new functions or classes shouldn't be
145
mentioned, but new commands, changes in behaviour or fixed nontrivial
146
bugs should be listed. See the existing entries for an idea of what
149
Within each release, entries in the news file should have the most
150
user-visible changes first. So the order should be approximately:
152
* changes to existing behaviour - the highest priority because the
153
user's existing knowledge is incorrect
154
* new features - should be brought to their attention
155
* bug fixes - may be of interest if the bug was affecting them, and
156
should include the bug number if any
157
* major documentation changes
158
* changes to internal interfaces
160
People who made significant contributions to each change are listed in
161
parenthesis. This can include reporting bugs (particularly with good
162
details or reproduction recipes), submitting patches, etc.
167
Functions, methods, classes and modules should have docstrings
168
describing how they are used.
170
The first line of the docstring should be a self-contained sentence.
172
For the special case of Command classes, this acts as the user-visible
173
documentation shown by the help command.
175
The docstrings should be formatted as reStructuredText_ (like this
176
document), suitable for processing using the epydoc_ tool into HTML
179
.. _reStructuredText: http://docutils.sourceforge.net/rst.html
180
.. _epydoc: http://epydoc.sourceforge.net/
187
Please write PEP-8__ compliant code.
189
One often-missed requirement is that the first line of docstrings
190
should be a self-contained one-sentence summary.
192
__ http://www.python.org/peps/pep-0008.html
199
Functions, methods or members that are in some sense "private" are given
200
a leading underscore prefix. This is just a hint that code outside the
201
implementation should probably not use that interface.
203
We prefer class names to be concatenated capital words (``TestCase``)
204
and variables, methods and functions to be lowercase words joined by
205
underscores (``revision_id``, ``get_revision``).
207
For the purposes of naming some names are treated as single compound
208
words: "filename", "revno".
210
Consider naming classes as nouns and functions/methods as verbs.
212
Try to avoid using abbreviations in names, because there can be
213
inconsistency if other people use the full name.
219
``revision_id`` not ``rev_id`` or ``revid``
221
Functions that transform one thing to another should be named ``x_to_y``
222
(not ``x2y`` as occurs in some old code.)
228
Python destructors (``__del__``) work differently to those of other
229
languages. In particular, bear in mind that destructors may be called
230
immediately when the object apparently becomes unreferenced, or at some
231
later time, or possibly never at all. Therefore we have restrictions on
232
what can be done inside them.
234
0. Never use a __del__ method without asking Martin/Robert first.
236
1. Never rely on a ``__del__`` method running. If there is code that
237
must run, do it from a ``finally`` block instead.
239
2. Never ``import`` from inside a ``__del__`` method, or you may crash the
242
3. In some places we raise a warning from the destructor if the object
243
has not been cleaned up or closed. This is considered OK: the warning
244
may not catch every case but it's still useful sometimes.
250
In some places we have variables which point to callables that construct
251
new instances. That is to say, they can be used a lot like class objects,
252
but they shouldn't be *named* like classes:
254
> I think that things named FooBar should create instances of FooBar when
255
> called. Its plain confusing for them to do otherwise. When we have
256
> something that is going to be used as a class - that is, checked for via
257
> isinstance or other such idioms, them I would call it foo_class, so that
258
> it is clear that a callable is not sufficient. If it is only used as a
259
> factory, then yes, foo_factory is what I would use.
265
Several places in Bazaar use (or will use) a registry, which is a
266
mapping from names to objects or classes. The registry allows for
267
loading in registered code only when it's needed, and keeping
268
associated information such as a help string or description.
274
To make startup time faster, we use the ``bzrlib.lazy_import`` module to
275
delay importing modules until they are actually used. ``lazy_import`` uses
276
the same syntax as regular python imports. So to import a few modules in a
279
from bzrlib.lazy_import import lazy_import
280
lazy_import(globals(), """
289
revision as _mod_revision,
291
import bzrlib.transport
295
At this point, all of these exist as a ``ImportReplacer`` object, ready to
296
be imported once a member is accessed. Also, when importing a module into
297
the local namespace, which is likely to clash with variable names, it is
298
recommended to prefix it as ``_mod_<module>``. This makes it clean that
299
the variable is a module, and these object should be hidden anyway, since
300
they shouldn't be imported into other namespaces.
303
Modules versus Members
304
~~~~~~~~~~~~~~~~~~~~~~
306
While it is possible for ``lazy_import()`` to import members of a module
307
when using the ``from module import member`` syntax, it is recommended to
308
only use that syntax to load sub modules ``from module import submodule``.
309
This is because variables and classes can frequently be used without
310
needing a sub-member for example::
312
lazy_import(globals(), """
313
from module import MyClass
317
return isinstance(x, MyClass)
319
This will incorrectly fail, because ``MyClass`` is a ``ImportReplacer``
320
object, rather than the real class.
323
Passing to other variables
324
~~~~~~~~~~~~~~~~~~~~~~~~~~
326
It also is incorrect to assign ``ImportReplacer`` objects to other variables.
327
Because the replacer only knows about the original name, it is unable to
328
replace other variables. The ``ImportReplacer`` class will raise an
329
``IllegalUseOfScopeReplacer`` exception if it can figure out that this
330
happened. But it requires accessing a member more than once from the new
331
variable, so some bugs are not detected right away.
388
337
(The strategy described here is what we want to get to, but it's not
419
368
should be only in the command-line tool.
422
Progress and Activity Indications
423
---------------------------------
425
bzrlib has a way for code to display to the user that stuff is happening
426
during a long operation. There are two particular types: *activity* which
427
means that IO is happening on a Transport, and *progress* which means that
428
higher-level application work is occurring. Both are drawn together by
431
Transport objects are responsible for calling `report_transport_activity`
434
Progress uses a model/view pattern: application code acts on a
435
`ProgressTask` object, which notifies the UI when it needs to be
436
displayed. Progress tasks form a stack. To create a new progress task on
437
top of the stack, call `bzrlib.ui.ui_factory.nested_progress_bar()`, then
438
call `update()` on the returned ProgressTask. It can be updated with just
439
a text description, with a numeric count, or with a numeric count and
440
expected total count. If an expected total count is provided the view
441
can show the progress moving along towards the expected total.
443
The user should call `finish` on the `ProgressTask` when the logical
444
operation has finished, so it can be removed from the stack.
446
Progress tasks have a complex relationship with generators: it's a very
447
good place to use them, but because python2.4 does not allow ``finally``
448
blocks in generators it's hard to clean them up properly. In this case
449
it's probably better to have the code calling the generator allocate a
450
progress task for its use and then call `finalize` when it's done, which
451
will close it if it was not already closed. The generator should also
452
finish the progress task when it exits, because it may otherwise be a long
453
time until the finally block runs.
459
When filenames or similar variables are presented inline within a message,
460
they should be enclosed in double quotes (ascii 0x22, not chiral unicode
463
bzr: ERROR: No such file "asdf"
465
When we print just a list of filenames there should not be any quoting:
468
.. _bug 544297: https://bugs.launchpad.net/bugs/544297
470
https://wiki.ubuntu.com/UnitsPolicy provides a good explanation about
471
which unit should be used when. Roughly speaking, IEC standard applies
472
for base-2 units and SI standard applies for base-10 units:
474
* for network bandwidth and disk sizes, use base-10 (Mbits/s, kB/s, GB)
476
* for RAM sizes, use base-2 (GiB, TiB)
483
Bazaar has online help for various topics through ``bzr help COMMAND`` or
484
equivalently ``bzr command -h``. We also have help on command options,
485
and on other help topics. (See ``help_topics.py``.)
487
As for python docstrings, the first paragraph should be a single-sentence
488
synopsis of the command. These are user-visible and should be prefixed with
489
``__doc__ =`` so help works under ``python -OO`` with docstrings stripped.
491
The help for options should be one or more proper sentences, starting with
492
a capital letter and finishing with a full stop (period).
494
All help messages and documentation should have two spaces between
498
Handling Errors and Exceptions
499
==============================
501
Commands should return non-zero when they encounter circumstances that
502
the user should really pay attention to - which includes trivial shell
505
Recommended values are:
508
1. Conflicts in merge-like operations, or changes are present in
509
diff-like operations.
510
2. Unrepresentable diff changes (i.e. binary files that we cannot show
512
3. An error or exception has occurred.
513
4. An internal error occurred (one that shows a traceback.)
515
Errors are handled through Python exceptions. Exceptions should be defined
516
inside bzrlib.errors, so that we can see the whole tree at a glance.
374
In general tests should be placed in a file named test_FOO.py where
375
FOO is the logical thing under test. That file should be placed in the
376
tests subdirectory under the package being tested.
378
For example, tests for merge3 in bzrlib belong in bzrlib/tests/test_merge3.py.
379
See bzrlib/selftest/test_sampler.py for a template test script.
381
Tests can be written for the UI or for individual areas of the library.
382
Choose whichever is appropriate: if adding a new command, or a new command
383
option, then you should be writing a UI test. If you are both adding UI
384
functionality and library functionality, you will want to write tests for
385
both the UI and the core behaviours. We call UI tests 'blackbox' tests
386
and they are found in ``bzrlib/tests/blackbox/*.py``.
388
When writing blackbox tests please honour the following conventions:
390
1. Place the tests for the command 'name' in
391
bzrlib/tests/blackbox/test_name.py. This makes it easy for developers
392
to locate the test script for a faulty command.
394
2. Use the 'self.run_bzr("name")' utility function to invoke the command
395
rather than running bzr in a subprocess or invoking the
396
cmd_object.run() method directly. This is a lot faster than
397
subprocesses and generates the same logging output as running it in a
398
subprocess (which invoking the method directly does not).
400
3. Only test the one command in a single test script. Use the bzrlib
401
library when setting up tests and when evaluating the side-effects of
402
the command. We do this so that the library api has continual pressure
403
on it to be as functional as the command line in a simple manner, and
404
to isolate knock-on effects throughout the blackbox test suite when a
405
command changes its name or signature. Ideally only the tests for a
406
given command are affected when a given command is changed.
408
4. If you have a test which does actually require running bzr in a
409
subprocess you can use ``run_bzr_subprocess``. By default the spawned
410
process will not load plugins unless ``--allow-plugins`` is supplied.
416
We make selective use of doctests__. In general they should provide
417
*examples* within the API documentation which can incidentally be tested. We
418
don't try to test every important case using doctests -- regular Python
419
tests are generally a better solution.
421
Most of these are in ``bzrlib/doc/api``. More additions are welcome.
423
__ http://docs.python.org/lib/module-doctest.html
428
Currently, bzr selftest is used to invoke tests.
429
You can provide a pattern argument to run a subset. For example,
430
to run just the blackbox tests, run::
432
./bzr selftest -v blackbox
434
To skip a particular test (or set of tests), you need to use a negative
437
./bzr selftest '^(?!.*blackbox)'
440
Errors and exceptions
441
=====================
443
Errors are handled through Python exceptions.
518
445
We broadly classify errors as either being either internal or not,
519
depending on whether ``internal_error`` is set or not. If we think it's our
446
depending on whether ``user_error`` is set or not. If we think it's our
520
447
fault, we show a backtrace, an invitation to report the bug, and possibly
521
448
other details. This is the default for errors that aren't specifically
522
449
recognized as being caused by a user error. Otherwise we show a briefer
543
470
that exception specifically, or when it needs a substantially different
546
#. If it is something that a caller can recover from, a custom exception
549
#. If it is a data consistency issue, using a builtin like
550
``ValueError``/``TypeError`` is reasonable.
552
#. If it is a programmer error (using an api incorrectly)
553
``AssertionError`` is reasonable.
555
#. Otherwise, use ``BzrError`` or ``InternalBzrError``.
557
473
Exception strings should start with a capital letter and should not have a
558
474
final fullstop. If long, they may contain newlines to break the text.
565
When you change bzrlib, please update the relevant documentation for the
566
change you made: Changes to commands should update their help, and
567
possibly end user tutorials; changes to the core library should be
568
reflected in API documentation.
573
If you make a user-visible change, please add a note to the NEWS file.
574
The description should be written to make sense to someone who's just
575
a user of bzr, not a developer: new functions or classes shouldn't be
576
mentioned, but new commands, changes in behaviour or fixed nontrivial
577
bugs should be listed. See the existing entries for an idea of what
580
Within each release, entries in the news file should have the most
581
user-visible changes first. So the order should be approximately:
583
* changes to existing behaviour - the highest priority because the
584
user's existing knowledge is incorrect
585
* new features - should be brought to their attention
586
* bug fixes - may be of interest if the bug was affecting them, and
587
should include the bug number if any
588
* major documentation changes, including fixed documentation bugs
589
* changes to internal interfaces
591
People who made significant contributions to each change are listed in
592
parenthesis. This can include reporting bugs (particularly with good
593
details or reproduction recipes), submitting patches, etc.
595
To help with merging, NEWS entries should be sorted lexicographically
601
The docstring of a command is used by ``bzr help`` to generate help output
602
for the command. The list 'takes_options' attribute on a command is used by
603
``bzr help`` to document the options for the command - the command
604
docstring does not need to document them. Finally, the '_see_also'
605
attribute on a command can be used to reference other related help topics.
610
Functions, methods, classes and modules should have docstrings
611
describing how they are used.
613
The first line of the docstring should be a self-contained sentence.
615
For the special case of Command classes, this acts as the user-visible
616
documentation shown by the help command.
618
The docstrings should be formatted as reStructuredText_ (like this
619
document), suitable for processing using the epydoc_ tool into HTML
622
.. _reStructuredText: http://docutils.sourceforge.net/rst.html
623
.. _epydoc: http://epydoc.sourceforge.net/
632
The copyright policy for bzr was recently made clear in this email (edited
633
for grammatical correctness)::
635
The attached patch cleans up the copyright and license statements in
636
the bzr source. It also adds tests to help us remember to add them
637
with the correct text.
639
We had the problem that lots of our files were "Copyright Canonical
640
Development Ltd" which is not a real company, and some other variations
641
on this theme. Also, some files were missing the GPL statements.
643
I want to be clear about the intent of this patch, since copyright can
644
be a little controversial.
646
1) The big motivation for this is not to shut out the community, but
647
just to clean up all of the invalid copyright statements.
649
2) It has been the general policy for bzr that we want a single
650
copyright holder for all of the core code. This is following the model
651
set by the FSF, which makes it easier to update the code to a new
652
license in case problems are encountered. (For example, if we want to
653
upgrade the project universally to GPL v3 it is much simpler if there is
654
a single copyright holder). It also makes it clearer if copyright is
655
ever debated, there is a single holder, which makes it easier to defend
656
in court, etc. (I think the FSF position is that if you assign them
657
copyright, they can defend it in court rather than you needing to, and
658
I'm sure Canonical would do the same).
659
As such, Canonical has requested copyright assignments from all of the
662
3) If someone wants to add code and not attribute it to Canonical, there
663
is a specific list of files that are excluded from this check. And the
664
test failure indicates where that is, and how to update it.
666
4) If anyone feels that I changed a copyright statement incorrectly, just
667
let me know, and I'll be happy to correct it. Whenever you have large
668
mechanical changes like this, it is possible to make some mistakes.
670
Just to reiterate, this is a community project, and it is meant to stay
671
that way. Core bzr code is copyright Canonical for legal reasons, and
672
the tests are just there to help us maintain that.
681
Bazaar has a few facilities to help debug problems by going into pdb_, the
684
.. _pdb: http://docs.python.org/lib/debugger-commands.html
686
If the ``BZR_PDB`` environment variable is set
687
then bzr will go into pdb post-mortem mode when an unhandled exception
690
If you send a SIGQUIT or SIGBREAK signal to bzr then it will drop into the
691
debugger immediately. SIGQUIT can be generated by pressing Ctrl-\\ on
692
Unix. SIGBREAK is generated with Ctrl-Pause on Windows (some laptops have
693
this as Fn-Pause). You can continue execution by typing ``c``. This can
694
be disabled if necessary by setting the environment variable
695
``BZR_SIGQUIT_PDB=0``.
701
Bazaar accepts some global options starting with ``-D`` such as
702
``-Dhpss``. These set a value in `bzrlib.debug.debug_flags`, and
703
typically cause more information to be written to the trace file. Most
704
`mutter` calls should be guarded by a check of those flags so that we
705
don't write out too much information if it's not needed.
707
Debug flags may have effects other than just emitting trace messages.
709
Run ``bzr help global-options`` to see them all.
711
These flags may also be set as a comma-separated list in the
712
``debug_flags`` option in e.g. ``~/.bazaar/bazaar.conf``. (Note that it
713
must be in this global file, not in the branch or location configuration,
714
because it's currently only loaded at startup time.) For instance you may
715
want to always record hpss traces and to see full error tracebacks::
717
debug_flags = hpss, error
726
484
indexes into the branch's revision history.
490
The ``Transport`` layer handles access to local or remote directories.
491
Each Transport object acts like a logical connection to a particular
492
directory, and it allows various operations on files within it. You can
493
*clone* a transport to get a new Transport connected to a subdirectory or
496
Transports are not used for access to the working tree. At present
497
working trees are always local and they are accessed through the regular
498
Python file io mechanisms.
503
Transports work in URLs. Take note that URLs are by definition only
504
ASCII - the decision of how to encode a Unicode string into a URL must be
505
taken at a higher level, typically in the Store. (Note that Stores also
506
escape filenames which cannot be safely stored on all filesystems, but
507
this is a different level.)
509
The main reason for this is that it's not possible to safely roundtrip a
510
URL into Unicode and then back into the same URL. The URL standard
511
gives a way to represent non-ASCII bytes in ASCII (as %-escapes), but
512
doesn't say how those bytes represent non-ASCII characters. (They're not
513
guaranteed to be UTF-8 -- that is common but doesn't happen everywhere.)
515
For example if the user enters the url ``http://example/%e0`` there's no
516
way to tell whether that character represents "latin small letter a with
517
grave" in iso-8859-1, or "latin small letter r with acute" in iso-8859-2
518
or malformed UTF-8. So we can't convert their URL to Unicode reliably.
520
Equally problematic if we're given a url-like string containing non-ascii
521
characters (such as the accented a) we can't be sure how to convert that
522
to the correct URL, because we don't know what encoding the server expects
523
for those characters. (Although this is not totally reliable we might still
524
accept these and assume they should be put into UTF-8.)
526
A similar edge case is that the url ``http://foo/sweet%2Fsour`` contains
527
one directory component whose name is "sweet/sour". The escaped slash is
528
not a directory separator. If we try to convert URLs to regular Unicode
529
paths this information will be lost.
531
This implies that Transports must natively deal with URLs; for simplicity
532
they *only* deal with URLs and conversion of other strings to URLs is done
533
elsewhere. Information they return, such as from ``list_dir``, is also in
534
the form of URL components.
729
537
Unicode and Encoding Support
730
538
============================
781
589
valid characters are generated where possible.
787
We write some extensions in C using pyrex. We design these to work in
790
* User with no C compiler
791
* User with C compiler
794
The recommended way to install bzr is to have a C compiler so that the
795
extensions can be built, but if no C compiler is present, the pure python
796
versions we supply will work, though more slowly.
798
For developers we recommend that pyrex be installed, so that the C
799
extensions can be changed if needed.
801
For the C extensions, the extension module should always match the
802
original python one in all respects (modulo speed). This should be
803
maintained over time.
805
To create an extension, add rules to setup.py for building it with pyrex,
806
and with distutils. Now start with an empty .pyx file. At the top add
807
"include 'yourmodule.py'". This will import the contents of foo.py into this
808
file at build time - remember that only one module will be loaded at
809
runtime. Now you can subclass classes, or replace functions, and only your
810
changes need to be present in the .pyx file.
812
Note that pyrex does not support all 2.4 programming idioms, so some
813
syntax changes may be required. I.e.
815
- 'from foo import (bar, gam)' needs to change to not use the brackets.
816
- 'import foo.bar as bar' needs to be 'import foo.bar; bar = foo.bar'
818
If the changes are too dramatic, consider
819
maintaining the python code twice - once in the .pyx, and once in the .py,
820
and no longer including the .py file.
823
Making Installers for OS Windows
595
If you'd like to propose a change, please post to the
596
bazaar@lists.canonical.com list with a patch, bzr changeset, or link to a
597
branch. Please put '[patch]' in the subject so we can pick them out, and
598
include some text explaining the change. Remember to put an update to the NEWS
599
file in your diff, if it makes any changes visible to users or plugin
600
developers. Please include a diff against mainline if you're giving a link to
603
Please indicate if you think the code is ready to merge, or if it's just a
604
draft or for discussion. If you want comments from many developers rather than
605
to be merged, you can put '[rfc]' in the subject lines.
607
Anyone is welcome to review code. There are broadly three gates for
610
* Doesn't reduce test coverage: if it adds new methods or commands,
611
there should be tests for them. There is a good test framework
612
and plenty of examples to crib from, but if you are having trouble
613
working out how to test something feel free to post a draft patch
616
* Doesn't reduce design clarity, such as by entangling objects
617
we're trying to separate. This is mostly something the more
618
experienced reviewers need to help check.
620
* Improves bugs, features, speed, or code simplicity.
622
Code that goes in should pass all three.
624
If you read a patch please reply and say so. We can use a numeric scale
625
of -1, -0, +0, +1, meaning respectively "really don't want it in current
626
form", "somewhat uncomfortable", "ok with me", and "please put it in".
627
Anyone can "vote". (It's not really voting, just a terse expression.)
629
If something gets say two +1 votes from core reviewers, and no
630
vetos, then it's OK to come in. Any of the core developers can bring it
631
into their integration branch, which I'll merge regularly. (If you do
632
so, please reply and say so.)
635
Making installers for OS Windows
824
636
================================
825
637
To build a win32 installer, see the instructions on the wiki page:
826
http://wiki.bazaar.canonical.com/BzrWin32Installer
834
What is a Core Developer?
835
-------------------------
837
While everyone in the Bazaar community is welcome and encouraged to
838
propose and submit changes, a smaller team is reponsible for pulling those
839
changes together into a cohesive whole. In addition to the general developer
840
stuff covered above, "core" developers have responsibility for:
843
* reviewing blueprints
845
* managing releases (see `Releasing Bazaar <http://doc.bazaar.canonical.com/developers/releasing.html>`_)
848
Removing barriers to community participation is a key reason for adopting
849
distributed VCS technology. While DVCS removes many technical barriers,
850
a small number of social barriers are often necessary instead.
851
By documenting how the above things are done, we hope to
852
encourage more people to participate in these activities, keeping the
853
differences between core and non-core contributors to a minimum.
856
Communicating and Coordinating
857
------------------------------
859
While it has many advantages, one of the challenges of distributed
860
development is keeping everyone else aware of what you're working on.
861
There are numerous ways to do this:
863
#. Assign bugs to yourself in Launchpad
864
#. Mention it on the mailing list
867
As well as the email notifcations that occur when merge requests are sent
868
and reviewed, you can keep others informed of where you're spending your
869
energy by emailing the **bazaar-commits** list implicitly. To do this,
870
install and configure the Email plugin. One way to do this is add these
871
configuration settings to your central configuration file (e.g.
872
``~/.bazaar/bazaar.conf``)::
875
email = Joe Smith <joe.smith@internode.on.net>
876
smtp_server = mail.internode.on.net:25
878
Then add these lines for the relevant branches in ``locations.conf``::
880
post_commit_to = bazaar-commits@lists.canonical.com
881
post_commit_mailer = smtplib
883
While attending a sprint, RobertCollins' Dbus plugin is useful for the
884
same reason. See the documentation within the plugin for information on
885
how to set it up and configure it.
896
Keeping on top of bugs reported is an important part of ongoing release
897
planning. Everyone in the community is welcome and encouraged to raise
898
bugs, confirm bugs raised by others, and nominate a priority. Practically
899
though, a good percentage of bug triage is often done by the core
900
developers, partially because of their depth of product knowledge.
902
With respect to bug triage, core developers are encouraged to play an
903
active role with particular attention to the following tasks:
905
* keeping the number of unconfirmed bugs low
906
* ensuring the priorities are generally right (everything as critical - or
907
medium - is meaningless)
908
* looking out for regressions and turning those around sooner rather than later.
911
As well as prioritizing bugs and nominating them against a
912
target milestone, Launchpad lets core developers offer to mentor others in
638
http://bazaar-vcs.org/BzrWin32Installer
641
:: vim: ft=rst tw=74 ai
added
removed
HACKING
