11
11
the Bazaar mailing list. To propose a correction or addition to this
12
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-vcs.org/developers/.
14
The current version of this document is available in the file
15
``doc/en/developer-guide/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>`_.
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If nothing else, perhaps you'll find inspiration in how other developers
41
47
have solved their challenges.
43
Finding Something To Do
44
=======================
46
Ad-hoc performance work can also be done. One useful tool is the 'evil' debug
47
flag. For instance running ``bzr -Devil commit -m "test"`` will log a backtrace
48
to the bzr log file for every method call which triggers a slow or non-scalable
49
part of the bzr library. So checking that a given command with ``-Devil`` has
50
no backtraces logged to the log file is a good way to find problem function
51
calls that might be nested deep in the code base.
53
50
Planning and Discussing Changes
54
51
===============================
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59
to involving the community before you spend much time on a change.
65
* you get to build on the wisdom of others, saving time
62
* you get to build on the wisdom on others, saving time
67
* if others can direct you to similar code, it minimises the work to be done
64
* if others can direct you to similar code, it minimises the work to be done
69
66
* it assists everyone in coordinating direction, priorities and effort.
76
73
Bazaar Development in a Nutshell
77
74
================================
79
.. was from bazaar-vcs.org/BzrGivingBack
81
One of the fun things about working on a version control system like Bazaar is
82
that the users have a high level of proficiency in contributing back into
83
the tool. Consider the following very brief introduction to contributing back
84
to Bazaar. More detailed instructions are in the following sections.
89
First, get a local copy of the development mainline (See `Why make a local
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$ bzr branch http://bazaar-vcs.org/bzr/bzr.dev/ bzr.dev
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Now make your own branch::
99
$ bzr branch bzr.dev 123456-my-bugfix
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This will give you a branch called "123456-my-bugfix" that you can work on
102
and commit in. Here, you can study the code, make a fix or a new feature.
103
Feel free to commit early and often (after all, it's your branch!).
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Documentation improvements are an easy place to get started giving back to the
106
Bazaar project. The documentation is in the `doc/` subdirectory of the Bazaar
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When you are done, make sure that you commit your last set of changes as well!
110
Once you are happy with your changes, ask for them to be merged, as described
113
Making a Merge Proposal
114
-----------------------
116
The Bazaar developers use Launchpad to further enable a truly distributed
117
style of development. Anyone can propose a branch for merging into the Bazaar
118
trunk. To start this process, you need to push your branch to Launchpad. To
119
do this, you will need a Launchpad account and user name, e.g.
120
`your_lp_username`. You can push your branch to Launchpad directly from
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$ bzr push lp:~your_lp_username/bzr/meaningful_name_here
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After you have pushed your branch, you will need to propose it for merging to
126
the Bazaar trunk. Go to
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<https://launchpad.net/your_lp_username/bzr/meaningful_name_here> and choose
128
"Propose for merging into another branch". Select "~bzr/bzr/trunk" to hand
129
your changes off to the Bazaar developers for review and merging.
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).
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Why make a local copy of bzr.dev?
139
---------------------------------
141
Making a local mirror of bzr.dev is not strictly necessary, but it means
143
- You can use that copy of bzr.dev as your main bzr executable, and keep it
144
up-to-date using ``bzr pull``.
145
- Certain operations are faster, and can be done when offline. For example:
148
- ``bzr diff -r ancestor:...``
151
- When it's time to create your next branch, it's more convenient. When you
152
have further contributions to make, you should do them in their own branch::
155
$ bzr branch bzr.dev additional_fixes
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$ cd additional_fixes # hack, hack, hack
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.
160
82
Understanding the Development Process
256
178
Holds documentation on a whole range of things on Bazaar from the
257
179
origination of ideas within the project to information on Bazaar
258
180
features and use cases. Within this directory there is a subdirectory
259
for each translation into a human language. All the documentation
181
for each translation into a human language. All the documentation
260
182
is in the ReStructuredText markup language.
263
Documentation specifically targeted at Bazaar and plugin developers.
185
Documentation specifically targetted at Bazaar and plugin developers.
264
186
(Including this document.)
268
Automatically-generated API reference information is available at
269
<http://starship.python.net/crew/mwh/bzrlibapi/>.
271
See also the `Bazaar Architectural Overview
272
<http://doc.bazaar-vcs.org/developers/overview.html>`_.
190
Automatically-generated API reference information is available at
191
<http://starship.python.net/crew/mwh/bzrlibapi/>.
193
See also the `Bazaar Architectural Overview <../../developers/overview.html>`_.
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196
The Code Review Process
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Proposing a merge through the web
403
324
---------------------------------
405
To create the proposal through the web, first push your branch to Launchpad.
406
For example, a branch dealing with documentation belonging to the Launchpad
407
User mbp could be pushed as ::
326
To create the propsal through the web: push your branch to Launchpad, eg::
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bzr push lp:~mbp/bzr/doc
411
Then go to the branch's web page, which in this case would be
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<https://code.launchpad.net/~mbp/bzr/doc>. You can simplify this step by just
330
then go to the branch's web page, which in this case would be
331
<https://code.launchpad.net/~mbp/bzr/doc>. You can automate that by just
417
You can then click "Propose for merging into another branch", and enter your
418
cover letter (see above) into the web form. Typically you'll want to merge
419
into ``~bzr/bzr/trunk`` which will be the default; you might also want to
420
nominate merging into a release branch for a bug fix. There is the option to
421
specify a specific reviewer or type of review, and you shouldn't normally
336
You can then click "Propose for merging into another branch", and enter a
337
cover letter into the web form. Typically you'll want to merge into
338
``~bzr/bzr/trunk`` which will be the default; you might also want to
339
nominate merging into a release branch for a bug fix. There is the option
340
to specify a specific reviewer or type of review, and you shouldn't
341
normally change those.
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Submitting the form takes you to the new page about the merge proposal
425
344
containing the diff of the changes, comments by interested people, and
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Functions, methods or members that are relatively private are given
550
Functions, methods or members that are "private" to bzrlib are given
632
551
a leading underscore prefix. Names without a leading underscore are
633
552
public not just across modules but to programmers using bzrlib as an
553
API. As a consequence, a leading underscore is appropriate for names
554
exposed across modules but that are not to be exposed to bzrlib API
636
557
We prefer class names to be concatenated capital words (``TestCase``)
637
558
and variables, methods and functions to be lowercase words joined by
679
600
may not catch every case but it's still useful sometimes.
685
Often when something has failed later code, including cleanups invoked
686
from ``finally`` blocks, will fail too. These secondary failures are
687
generally uninteresting compared to the original exception. So use the
688
``only_raises`` decorator (from ``bzrlib.decorators``) for methods that
689
are typically called in ``finally`` blocks, such as ``unlock`` methods.
690
For example, ``@only_raises(LockNotHeld, LockBroken)``. All errors that
691
are unlikely to be a knock-on failure from a previous failure should be
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606
In some places we have variables which point to callables that construct
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607
new instances. That is to say, they can be used a lot like class objects,
700
but they shouldn't be *named* like classes::
608
but they shouldn't be *named* like classes:
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> I think that things named FooBar should create instances of FooBar when
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> called. Its plain confusing for them to do otherwise. When we have
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The ``InterObject`` provides for two-way `multiple dispatch`__: matching
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up for example a source and destination repository to find the right way
724
to transfer data between them.
632
to transfer data between them.
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.. __: http://en.wikipedia.org/wiki/Multiple_dispatch
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There is a subclass ``InterObject`` classes for each type of object that is
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dispatched this way, e.g. ``InterRepository``. Calling ``.get()`` on this
730
class will return an ``InterObject`` instance providing the best match for
638
class will return an ``InterObject`` instance providing the best match for
731
639
those parameters, and this instance then has methods for operations
732
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between the objects.
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inter = InterRepository.get(source_repo, target_repo)
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inter.fetch(revision_id)
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773
Evolving Interfaces
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===================
871
We don't change APIs in stable branches: any supported symbol in a stable
872
release of bzr must not be altered in any way that would result in
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We have a commitment to 6 months API stability - any supported symbol in a
777
release of bzr MUST NOT be altered in any way that would result in
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778
breaking existing code that uses it. That means that method names,
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parameter ordering, parameter names, variable and attribute names etc must
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not be changed without leaving a 'deprecated forwarder' behind. This even
879
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way, you need to change its name as well. For instance, if I add an optional keyword
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parameter to branch.commit - that's fine. On the other hand, if I add a
881
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keyword parameter to branch.commit which is a *required* transaction
882
object, I should rename the API - i.e. to 'branch.commit_transaction'.
884
(Actually, that may break code that provides a new implementation of
885
``commit`` and doesn't expect to receive the parameter.)
787
object, I should rename the API - i.e. to 'branch.commit_transaction'.
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When renaming such supported API's, be sure to leave a deprecated_method (or
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_function or ...) behind which forwards to the new API. See the
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bzrlib.symbol_versioning module for decorators that take care of the
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details for you - such as updating the docstring, and issuing a warning
891
when the old API is used.
793
when the old api is used.
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For unsupported API's, it does not hurt to follow this discipline, but it's
894
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not required. Minimally though, please try to rename things so that
1021
923
time until the finally block runs.
1027
When filenames or similar variables are presented inline within a message,
1028
they should be enclosed in double quotes (ascii 0x22, not chiral unicode
1031
bzr: ERROR: No such file "asdf"
1033
When we print just a list of filenames there should not be any quoting:
1036
.. _bug 544297: https://bugs.launchpad.net/bugs/544297
1038
https://wiki.ubuntu.com/UnitsPolicy provides a good explanation about
1039
which unit should be used when. Roughly speaking, IEC standard applies
1040
for base-2 units and SI standard applies for base-10 units:
1042
* for network bandwidth and disk sizes, use base-10 (Mbits/s, kB/s, GB)
1044
* for RAM sizes, use base-2 (GiB, TiB)
1114
991
#. If it is something that a caller can recover from, a custom exception
1117
994
#. If it is a data consistency issue, using a builtin like
1118
``ValueError``/``TypeError`` is reasonable.
995
``ValueError``/``TypeError`` is reasonable.
1120
997
#. If it is a programmer error (using an api incorrectly)
1121
``AssertionError`` is reasonable.
998
``AssertionError`` is reasonable.
1123
1000
#. Otherwise, use ``BzrError`` or ``InternalBzrError``.
1177
1054
Within each release, entries in the news file should have the most
1178
1055
user-visible changes first. So the order should be approximately:
1180
* changes to existing behaviour - the highest priority because the
1057
* changes to existing behaviour - the highest priority because the
1181
1058
user's existing knowledge is incorrect
1182
1059
* new features - should be brought to their attention
1183
1060
* bug fixes - may be of interest if the bug was affecting them, and
1184
1061
should include the bug number if any
1185
* major documentation changes, including fixed documentation bugs
1062
* major documentation changes
1186
1063
* changes to internal interfaces
1188
1065
People who made significant contributions to each change are listed in
1189
1066
parenthesis. This can include reporting bugs (particularly with good
1190
1067
details or reproduction recipes), submitting patches, etc.
1192
To help with merging, NEWS entries should be sorted lexicographically
1193
within each section.
1236
1110
We had the problem that lots of our files were "Copyright Canonical
1237
1111
Development Ltd" which is not a real company, and some other variations
1238
1112
on this theme. Also, some files were missing the GPL statements.
1240
1114
I want to be clear about the intent of this patch, since copyright can
1241
1115
be a little controversial.
1243
1117
1) The big motivation for this is not to shut out the community, but
1244
1118
just to clean up all of the invalid copyright statements.
1246
1120
2) It has been the general policy for bzr that we want a single
1247
1121
copyright holder for all of the core code. This is following the model
1248
1122
set by the FSF, which makes it easier to update the code to a new
1255
1129
I'm sure Canonical would do the same).
1256
1130
As such, Canonical has requested copyright assignments from all of the
1257
1131
major contributers.
1259
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3) If someone wants to add code and not attribute it to Canonical, there
1260
1134
is a specific list of files that are excluded from this check. And the
1261
1135
test failure indicates where that is, and how to update it.
1263
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4) If anyone feels that I changed a copyright statement incorrectly, just
1264
1138
let me know, and I'll be happy to correct it. Whenever you have large
1265
1139
mechanical changes like this, it is possible to make some mistakes.
1267
1141
Just to reiterate, this is a community project, and it is meant to stay
1268
1142
that way. Core bzr code is copyright Canonical for legal reasons, and
1269
1143
the tests are just there to help us maintain that.
1281
1155
.. _pdb: http://docs.python.org/lib/debugger-commands.html
1283
If the ``BZR_PDB`` environment variable is set
1157
If the ``BZR_PDB`` environment variable is set
1284
1158
then bzr will go into pdb post-mortem mode when an unhandled exception
1287
If you send a SIGQUIT or SIGBREAK signal to bzr then it will drop into the
1288
debugger immediately. SIGQUIT can be generated by pressing Ctrl-\\ on
1289
Unix. SIGBREAK is generated with Ctrl-Pause on Windows (some laptops have
1290
this as Fn-Pause). You can continue execution by typing ``c``. This can
1291
be disabled if necessary by setting the environment variable
1292
``BZR_SIGQUIT_PDB=0``.
1161
If you send a SIGQUIT signal to bzr, which can be done by pressing
1162
Ctrl-\\ on Unix, bzr will go into the debugger immediately. You can
1163
continue execution by typing ``c``. This can be disabled if necessary
1164
by setting the environment variable ``BZR_SIGQUIT_PDB=0``.
1348
1220
for automated processing.
1349
1221
For example: ``bzr log`` should not fail if one of the entries has text
1350
1222
that cannot be displayed.
1353
1225
Attempting to print an unprintable character will cause a UnicodeError.
1354
1226
This is for commands that are intended more as scripting support, rather
1355
1227
than plain user review.
1356
For example: ``bzr ls`` is designed to be used with shell scripting. One
1357
use would be ``bzr ls --null --unknowns | xargs -0 rm``. If ``bzr``
1228
For exampl: ``bzr ls`` is designed to be used with shell scripting. One
1229
use would be ``bzr ls --null --unknows | xargs -0 rm``. If ``bzr``
1358
1230
printed a filename with a '?', the wrong file could be deleted. (At the
1359
1231
very least, the correct file would not be deleted). An error is used to
1360
1232
indicate that the requested action could not be performed.
1363
1235
Do not attempt to automatically convert Unicode strings. This is used
1364
1236
for commands that must handle conversion themselves.
1413
1285
To create an extension, add rules to setup.py for building it with pyrex,
1414
1286
and with distutils. Now start with an empty .pyx file. At the top add
1415
"include 'yourmodule.py'". This will import the contents of foo.py into this
1287
"include 'yourmodule.py'". This will import the contents of foo.py into this
1416
1288
file at build time - remember that only one module will be loaded at
1417
1289
runtime. Now you can subclass classes, or replace functions, and only your
1418
1290
changes need to be present in the .pyx file.
1420
1292
Note that pyrex does not support all 2.4 programming idioms, so some
1421
syntax changes may be required. I.e.
1293
syntax changes may be required. I.e.
1423
- 'from foo import (bar, gam)' needs to change to not use the brackets.
1424
- 'import foo.bar as bar' needs to be 'import foo.bar; bar = foo.bar'
1295
- 'from foo import (bar, gam)' needs to change to not use the brackets.
1296
- 'import foo.bar as bar' needs to be 'import foo.bar; bar = foo.bar'
1426
1298
If the changes are too dramatic, consider
1427
1299
maintaining the python code twice - once in the .pyx, and once in the .py,
1659
1531
https://blueprints.launchpad.net/bzr/. Once a blueprint for ready for
1660
1532
review, please announce it on the mailing list.
1662
Alternatively, send an email beginning with [RFC] with the proposal to the
1534
Alternatively, send an email begining with [RFC] with the proposal to the
1663
1535
list. In some cases, you may wish to attach proposed code or a proposed
1664
1536
developer document if that best communicates the idea. Debate can then
1665
1537
proceed using the normal merge review processes.
1677
1549
Planning Releases
1678
1550
=================
1555
As the two senior developers, Martin Pool and Robert Collins coordinate
1556
the overall Bazaar product development roadmap. Core developers provide
1557
input and review into this, particularly during sprints. It's totally
1558
expected that community members ought to be working on things that
1559
interest them the most. The roadmap is valuable though because it provides
1560
context for understanding where the product is going as a whole and why.
1681
1563
Using Releases and Milestones in Launchpad
1682
1564
------------------------------------------
added
removed
doc/en/developer-guide/HACKING.txt
