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core improvements should be tested closer to the code that is doing the
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work. Command line level tests should be placed in 'blackbox.py'.
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* Before fixing a bug, write a test case so that it does not regress.
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* Try to practice Test-Driven Development. before fixing a bug, write a
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test case so that it does not regress. Similarly for adding a new
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feature: write a test case for a small version of the new feature before
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starting on the code itself. Check the test fails on the old code, then
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add the feature or fix and check it passes.
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* Exceptions should be defined inside bzrlib.errors, so that we can
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31
see the whole tree at a glance.
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* Module names should always be given fully-qualified,
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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
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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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53
Evolving interfaces
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-------------------
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If you change the behaviour of an API in an incompatible way, please
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be sure to change its name as well. For instance, if I add a keyword
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parameter to branch.commit - that's fine. On the other hand, if I add
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a 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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This will prevent users of the old api getting surprising results.
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Instead, they will get an Attribute error as the api is missing, and
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will know to update their code. If in doubt, just ask on #bzr.
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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
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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.
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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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(not ``x2y`` as occurs in some old code.)
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Python destructors (``__del__``) work differently to those of other
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languages. In particular, bear in mind that destructors may be called
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immediately when the object apparently becomes unreferenced, or at some
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later time, or possibly never at all. Therefore we have restrictions on
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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
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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
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3. In some places we raise a warning from the destructor if the object
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has not been cleaned up or closed. This is considered OK: the warning
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may not catch every case but it's still useful sometimes.
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Integer identifier for a revision on the main line of a branch.
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Revision 0 is always the null revision; others are 1-based
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indexes into the branch's revision history.
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If you'd like to propose a change, please post to the
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bazaar-ng@lists.canonical.com list with a patch, bzr changeset, or link to a
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branch. Please put '[patch]' in the subject so we can pick them out, and
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include some text explaining the change. Remember to put an update to the NEWS
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file in your diff, if it makes any changes visible to users or plugin
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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
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draft or for discussion. If you want comments from many developers rather than
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to be merged, you can put '[rfc]' in the subject lines.
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Anyone is welcome to review code. There are broadly three gates for
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* Doesn't reduce test coverage: if it adds new methods or commands,
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there should be tests for them. There is a good test framework
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and plenty of examples to crib from, but if you are having trouble
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working out how to test something feel free to post a draft patch
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* Doesn't reduce design clarity, such as by entangling objects
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we're trying to separate. This is mostly something the more
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experienced reviewers need to help check.
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* Improves bugs, features, speed, or code simplicity.
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Code that goes in should pass all three.
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If you read a patch please reply and say so. We can use a numeric scale
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of -1, -0, +0, +1, meaning respectively "really don't want it in current
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form", "somewhat uncomfortable", "ok with me", and "please put it in".
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Anyone can "vote". (It's not really voting, just a terse expression.)
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If something gets say two +1 votes from core reviewers, and no
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vetos, then it's OK to come in. Any of the core developers can bring it
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into their integration branch, which I'll merge regularly. (If you do
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so, please reply and say so.)
added
removed
HACKING
