20
30
function runs. Import statements have a cost, so try to make sure
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31
they don't run inside hot functions.
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* Please write PEP-8__ compliant code.
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__ http://www.python.org/peps/pep-0008.html
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33
* Module names should always be given fully-qualified,
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34
i.e. ``bzrlib.hashcache`` not just ``hashcache``.
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* Commands should return non-zero when they encounter circumstances that
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the user should really pay attention to - which includes trivial shell
40
Recommended values are
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1- Conflicts in merge-like operations, or changes are present in
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2- Unrepresentable diff changes (i.e. binary files that we cannot show
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3- An error or exception has occurred.
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We have a commitment to 6 months API stability - any supported symbol in a
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release of bzr MUST NOT be altered in any way that would result in
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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
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applies to modules and classes.
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If you wish to change the behaviour of a supported API in an incompatible
59
way, you need to change its name as well. For instance, if I add a optional keyword
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parameter to branch.commit - that's fine. On the other hand, if I add a
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keyword parameter to branch.commit which is a *required* transaction
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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
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when the old api is used.
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For unsupported API's, it does not hurt to follow this discipline, but its
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not required. Minimally though, please try to rename things so that
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callers will at least get an AttributeError rather than weird results.
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Standard parameter types
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------------------------
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There are some common requirements in the library: some parameters need to be
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unicode safe, some need byte strings, and so on. At the moment we have
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only codified one specific pattern: Parameters that need to be unicode
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should be check via 'bzrlib.osutils.safe_unicode'. This will coerce the
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input into unicode in a consistent fashion, allowing trivial strings to be
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used for programmer convenience, but not performing unpredictably in the
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presence of different locales.
35
89
If you change the behaviour of a command, please update its docstring
36
90
in bzrlib/commands.py. This is displayed by the 'bzr help' command.
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95
If you make a user-visible change, please add a note to the NEWS file.
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The description should be written to make sense to someone who's just
40
97
a user of bzr, not a developer: new functions or classes shouldn't be
41
98
mentioned, but new commands, changes in behaviour or fixed nontrivial
42
99
bugs should be listed. See the existing entries for an idea of what
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Within each release, entries in the news file should have the most
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user-visible changes first. So the order should be approximately:
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* changes to existing behaviour - the highest priority because the
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user's existing knowledge is incorrect
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* new features - should be brought to their attention
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* bug fixes - may be of interest if the bug was affecting them, and
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should include the bug number if any
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* major documentation changes
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* changes to internal interfaces
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People who made significant contributions to each change are listed in
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parenthesis. This can include reporting bugs (particularly with good
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details or reproduction recipes), submitting patches, etc.
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Functions, methods, classes and modules should have docstrings
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describing how they are used.
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The first line of the docstring should be a self-contained sentence.
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For the special case of Command classes, this acts as the user-visible
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documentation shown by the help command.
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The docstrings should be formatted as reStructuredText_ (like this
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document), suitable for processing using the epydoc_ tool into HTML
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.. _reStructuredText: http://docutils.sourceforge.net/rst.html
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.. _epydoc: http://epydoc.sourceforge.net/
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Please write PEP-8__ compliant code.
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One often-missed requirement is that the first line of docstrings
143
should be a self-contained one-sentence summary.
145
__ http://www.python.org/peps/pep-0008.html
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Functions, methods or members that are in some sense "private" are given
153
a leading underscore prefix. This is just a hint that code outside the
154
implementation should probably not use that interface.
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We prefer class names to be concatenated capital words (``TestCase``)
157
and variables, methods and functions to be lowercase words joined by
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underscores (``revision_id``, ``get_revision``).
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For the purposes of naming some names are treated as single compound
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words: "filename", "revno".
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Consider naming classes as nouns and functions/methods as verbs.
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``revision_id`` not ``rev_id`` or ``revid``
171
Functions that transform one thing to another should be named ``x_to_y``
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(not ``x2y`` as occurs in some old code.)
178
Python destructors (``__del__``) work differently to those of other
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languages. In particular, bear in mind that destructors may be called
180
immediately when the object apparently becomes unreferenced, or at some
181
later time, or possibly never at all. Therefore we have restrictions on
182
what can be done inside them.
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0. Never use a __del__ method without asking Martin/Robert first.
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1. Never rely on a ``__del__`` method running. If there is code that
187
must run, do it from a ``finally`` block instead.
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2. Never ``import`` from inside a ``__del__`` method, or you may crash the
192
3. In some places we raise a warning from the destructor if the object
193
has not been cleaned up or closed. This is considered OK: the warning
194
may not catch every case but it's still useful sometimes.
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(The strategy described here is what we want to get to, but it's not
201
consistently followed in the code at the moment.)
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bzrlib is intended to be a generically reusable library. It shouldn't
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write messages to stdout or stderr, because some programs that use it
205
might want to display that information through a GUI or some other
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We can distinguish two types of output from the library:
210
1. Structured data representing the progress or result of an
211
operation. For example, for a commit command this will be a list
212
of the modified files and the finally committed revision number
215
These should be exposed either through the return code or by calls
216
to a callback parameter.
218
A special case of this is progress indicators for long-lived
219
operations, where the caller should pass a ProgressBar object.
221
2. Unstructured log/debug messages, mostly for the benefit of the
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developers or users trying to debug problems. This should always
223
be sent through ``bzrlib.trace`` and Python ``logging``, so that
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it can be redirected by the client.
226
The distinction between the two is a bit subjective, but in general if
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there is any chance that a library would want to see something as
228
structured data, we should make it so.
230
The policy about how output is presented in the text-mode client
231
should be only in the command-line tool.
236
In general tests should be placed in a file named test_FOO.py where
237
FOO is the logical thing under test. That file should be placed in the
238
tests subdirectory under the package being tested.
240
For example, tests for merge3 in bzrlib belong in bzrlib/tests/test_merge3.py.
241
See bzrlib/selftest/test_sampler.py for a template test script.
243
Tests can be written for the UI or for individual areas of the library.
244
Choose whichever is appropriate: if adding a new command, or a new command
245
option, then you should be writing a UI test. If you are both adding UI
246
functionality and library functionality, you will want to write tests for
247
both the UI and the core behaviours. We call UI tests 'blackbox' tests
248
and they are found in bzrlib/tests/blackbox/*.py.
250
When writing blackbox tests please honour the following conventions:
252
1. Place the tests for the command 'name' in
253
bzrlib/tests/blackbox/test_name.py. This makes it easy for developers
254
to locate the test script for a faulty command.
256
2. Use the 'self.run_bzr("name")' utility function to invoke the command
257
rather than running bzr in a subprocess or invoking the
258
cmd_object.run() method directly. This is a lot faster than
259
subprocesses and generates the same logging output as running it in a
260
subprocess (which invoking the method directly does not).
262
3. Only test the one command in a single test script. Use the bzrlib
263
library when setting up tests and when evaluating the side-effects of
264
the command. We do this so that the library api has continual pressure
265
on it to be as functional as the command line in a simple manner, and
266
to isolate knock-on effects throughout the blackbox test suite when a
267
command changes it name or signature. Ideally only the tests for a
268
given command are affected when a given command is changed.
272
Currently, bzr selftest is used to invoke tests.
273
You can provide a pattern argument to run a subset. For example,
274
to run just the blackbox tests, run::
276
./bzr selftest -v blackbox
279
Errors and exceptions
280
=====================
282
Errors are handled through Python exceptions. They can represent user
283
errors, environmental errors or program bugs. Sometimes we can't be sure
284
at the time it's raised which case applies. See bzrlib/errors.py for
285
details on the error-handling practices.
292
Integer identifier for a revision on the main line of a branch.
293
Revision 0 is always the null revision; others are 1-based
294
indexes into the branch's revision history.
300
If you'd like to propose a change, please post to the
301
bazaar-ng@lists.canonical.com list with a patch, bzr changeset, or link to a
302
branch. Please put '[patch]' in the subject so we can pick them out, and
303
include some text explaining the change. Remember to put an update to the NEWS
304
file in your diff, if it makes any changes visible to users or plugin
305
developers. Please include a diff against mainline if you're giving a link to
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Please indicate if you think the code is ready to merge, or if it's just a
309
draft or for discussion. If you want comments from many developers rather than
310
to be merged, you can put '[rfc]' in the subject lines.
312
Anyone is welcome to review code. There are broadly three gates for
315
* Doesn't reduce test coverage: if it adds new methods or commands,
316
there should be tests for them. There is a good test framework
317
and plenty of examples to crib from, but if you are having trouble
318
working out how to test something feel free to post a draft patch
321
* Doesn't reduce design clarity, such as by entangling objects
322
we're trying to separate. This is mostly something the more
323
experienced reviewers need to help check.
325
* Improves bugs, features, speed, or code simplicity.
327
Code that goes in should pass all three.
329
If you read a patch please reply and say so. We can use a numeric scale
330
of -1, -0, +0, +1, meaning respectively "really don't want it in current
331
form", "somewhat uncomfortable", "ok with me", and "please put it in".
332
Anyone can "vote". (It's not really voting, just a terse expression.)
334
If something gets say two +1 votes from core reviewers, and no
335
vetos, then it's OK to come in. Any of the core developers can bring it
336
into their integration branch, which I'll merge regularly. (If you do
337
so, please reply and say so.)
added
removed
HACKING
