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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 an optional keyword
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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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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 checked via ``bzrlib.osutils.safe_unicode``. This will coerce the
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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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The copyright policy for bzr was recently made clear in this email (edited
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for grammatical correctness)::
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The attached patch cleans up the copyright and license statements in
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the bzr source. It also adds tests to help us remember to add them
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with the correct text.
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We had the problem that lots of our files were "Copyright Canonical
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Development Ltd" which is not a real company, and some other variations
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on this theme. Also, some files were missing the GPL statements.
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I want to be clear about the intent of this patch, since copyright can
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be a little controversial.
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1) The big motivation for this is not to shut out the community, but
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just to clean up all of the invalid copyright statements.
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2) It has been the general policy for bzr that we want a single
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copyright holder for all of the core code. This is following the model
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set by the FSF, which makes it easier to update the code to a new
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license in case problems are encountered. (For example, if we want to
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upgrade the project universally to GPL v3 it is much simpler if there is
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a single copyright holder). It also makes it clearer if copyright is
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ever debated, there is a single holder, which makes it easier to defend
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in court, etc. (I think the FSF position is that if you assign them
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copyright, they can defend it in court rather than you needing to, and
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I'm sure Canonical would do the same).
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As such, Canonical has requested copyright assignments from all of the
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3) If someone wants to add code and not attribute it to Canonical, there
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is a specific list of files that are excluded from this check. And the
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test failure indicates where that is, and how to update it.
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4) If anyone feels that I changed a copyright statement incorrectly, just
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let me know, and I'll be happy to correct it. Whenever you have large
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mechanical changes like this, it is possible to make some mistakes.
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Just to reiterate, this is a community project, and it is meant to stay
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that way. Core bzr code is copyright Canonical for legal reasons, and
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the tests are just there to help us maintain that.
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When you change bzrlib, please update the relevant documentation for the
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change you made: Changes to commands should update their help, and
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possibly end user tutorials; changes to the core library should be
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reflected in API documentation.
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The docstring of a command is used by ``bzr help`` to generate help output
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for the command. The list 'takes_options' attribute on a command is used by
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``bzr help`` to document the options for the command - the command
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docstring does not need to document them. Finally, the '_see_also'
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attribute on a command can be used to reference other related help topics.
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If you change the behaviour of a command, please update its docstring
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in bzrlib/commands.py. This is displayed by the 'bzr help' command.
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209
> factory, then yes, foo_factory is what I would use.
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Several places in Bazaar use (or will use) a registry, which is a
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mapping from names to objects or classes. The registry allows for
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loading in registered code only when it's needed, and keeping
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associated information such as a help string or description.
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To make startup time faster, we use the ``bzrlib.lazy_import`` module to
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delay importing modules until they are actually used. ``lazy_import`` uses
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the same syntax as regular python imports. So to import a few modules in a
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from bzrlib.lazy_import import lazy_import
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lazy_import(globals(), """
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revision as _mod_revision,
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import bzrlib.transport
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At this point, all of these exist as a ``ImportReplacer`` object, ready to
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be imported once a member is accessed. Also, when importing a module into
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the local namespace, which is likely to clash with variable names, it is
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recommended to prefix it as ``_mod_<module>``. This makes it clearer that
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the variable is a module, and these object should be hidden anyway, since
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they shouldn't be imported into other namespaces.
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Modules versus Members
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~~~~~~~~~~~~~~~~~~~~~~
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While it is possible for ``lazy_import()`` to import members of a module
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when using the ``from module import member`` syntax, it is recommended to
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only use that syntax to load sub modules ``from module import submodule``.
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This is because variables and classes can frequently be used without
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needing a sub-member for example::
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lazy_import(globals(), """
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from module import MyClass
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return isinstance(x, MyClass)
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This will incorrectly fail, because ``MyClass`` is a ``ImportReplacer``
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object, rather than the real class.
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Passing to other variables
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~~~~~~~~~~~~~~~~~~~~~~~~~~
337
It also is incorrect to assign ``ImportReplacer`` objects to other variables.
338
Because the replacer only knows about the original name, it is unable to
339
replace other variables. The ``ImportReplacer`` class will raise an
340
``IllegalUseOfScopeReplacer`` exception if it can figure out that this
341
happened. But it requires accessing a member more than once from the new
342
variable, so some bugs are not detected right away.
413
279
the command. We do this so that the library api has continual pressure
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on it to be as functional as the command line in a simple manner, and
415
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to isolate knock-on effects throughout the blackbox test suite when a
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command changes its name or signature. Ideally only the tests for a
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command changes it name or signature. Ideally only the tests for a
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given command are affected when a given command is changed.
419
4. If you have a test which does actually require running bzr in a
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subprocess you can use ``run_bzr_subprocess``. By default the spawned
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process will not load plugins unless ``--allow-plugins`` is supplied.
443
304
./bzr selftest -v blackbox
445
To skip a particular test (or set of tests), use the --exclude option
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(shorthand -x) like so::
448
./bzr selftest -v -x blackbox
450
To list tests without running them, use the --list-only option like so::
452
./bzr selftest --list-only
454
This option can be combined with other selftest options (like -x) and
455
filter patterns to understand their effect.
306
To skip a particular test (or set of tests), you need to use a negative
309
./bzr selftest '^(?!.*blackbox)'
458
312
Errors and exceptions
459
313
=====================
461
Errors are handled through Python exceptions.
463
We broadly classify errors as either being either internal or not,
464
depending on whether ``user_error`` is set or not. If we think it's our
465
fault, we show a backtrace, an invitation to report the bug, and possibly
466
other details. This is the default for errors that aren't specifically
467
recognized as being caused by a user error. Otherwise we show a briefer
468
message, unless -Derror was given.
470
Many errors originate as "environmental errors" which are raised by Python
471
or builtin libraries -- for example IOError. These are treated as being
472
our fault, unless they're caught in a particular tight scope where we know
473
that they indicate a user errors. For example if the repository format
474
is not found, the user probably gave the wrong path or URL. But if one of
475
the files inside the repository is not found, then it's our fault --
476
either there's a bug in bzr, or something complicated has gone wrong in
477
the environment that means one internal file was deleted.
479
Many errors are defined in ``bzrlib/errors.py`` but it's OK for new errors
480
to be added near the place where they are used.
482
Exceptions are formatted for the user by conversion to a string
483
(eventually calling their ``__str__`` method.) As a convenience the
484
``._fmt`` member can be used as a template which will be mapped to the
485
error's instance dict.
487
New exception classes should be defined when callers might want to catch
488
that exception specifically, or when it needs a substantially different
491
Exception strings should start with a capital letter and should not have a
492
final fullstop. If long, they may contain newlines to break the text.
499
Bazaar has a few facilities to help debug problems by going into pdb_, the
502
.. _pdb: http://docs.python.org/lib/debugger-commands.html
504
If the ``BZR_PDB`` environment variable is set
505
then bzr will go into pdb post-mortem mode when an unhandled exception
508
If you send a SIGQUIT signal to bzr, which can be done by pressing C-\ on Unix,
509
bzr will go into the debugger immediately. You can continue execution by
510
typing ``c``. This can be disabled if necessary by setting the
511
environment variable ``BZR_SIGQUIT_PDB=0``.
315
Errors are handled through Python exceptions. They can represent user
316
errors, environmental errors or program bugs. Sometimes we can't be sure
317
at the time it's raised which case applies. See bzrlib/errors.py for
318
details on the error-handling practices.
626
432
valid characters are generated where possible.
632
The ``bzrlib.osutils`` module has many useful helper functions, including
633
some more portable variants of functions in the standard library.
635
In particular, don't use ``shutil.rmtree`` unless it's acceptable for it
636
to fail on Windows if some files are readonly or still open elsewhere.
637
Use ``bzrlib.osutils.rmtree`` instead.
640
435
Merge/review process
641
436
====================
643
438
If you'd like to propose a change, please post to the
644
bazaar@lists.canonical.com list with a patch, bzr changeset, or link to a
439
bazaar-ng@lists.canonical.com list with a patch, bzr changeset, or link to a
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440
branch. Please put '[patch]' in the subject so we can pick them out, and
646
441
include some text explaining the change. Remember to put an update to the NEWS
647
442
file in your diff, if it makes any changes visible to users or plugin
680
475
so, please reply and say so.)
686
We write some extensions in C using pyrex. We design these to work in
689
* User with no C compiler
690
* User with C compiler
693
The recommended way to install bzr is to have a C compiler so that the
694
extensions can be built, but if no C compiler is present, the pure python
695
versions we supply will work, though more slowly.
697
For developers we recommend that pyrex be installed, so that the C
698
extensions can be changed if needed.
700
For the C extensions, the extension module should always match the
701
original python one in all respects (modulo speed). This should be
702
maintained over time.
704
To create an extension, add rules to setup.py for building it with pyrex,
705
and with distutils. Now start with an empty .pyx file. At the top add
706
"include 'yourmodule.py'". This will import the contents of foo.py into this
707
file at build time - remember that only one module will be loaded at
708
runtime. Now you can subclass classes, or replace functions, and only your
709
changes need to be present in the .pyx file.
711
Note that pyrex does not support all 2.4 programming idioms, so some
712
syntax changes may be required. I.e.
714
- 'from foo import (bar, gam)' needs to change to not use the brackets.
715
- 'import foo.bar as bar' needs to be 'import foo.bar; bar = foo.bar'
717
If the changes are too dramatic, consider
718
maintaining the python code twice - once in the .pyx, and once in the .py,
719
and no longer including the .py file.
721
Making installers for OS Windows
722
================================
723
To build a win32 installer, see the instructions on the wiki page:
724
http://bazaar-vcs.org/BzrWin32Installer
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:: vim: ft=rst tw=74 ai
added
removed
HACKING
