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)
7
(The current version of this document is available in the file
8
``doc/developers/HACKING.txt`` in the source tree, or at
9
http://doc.bazaar-vcs.org/bzr.dev/en/developer-guide/HACKING.html)
15
Exploring the Bazaar Platform
16
=============================
18
Before making changes, it's a good idea to explore the work already
19
done by others. Perhaps the new feature or improvement you're looking
20
for is available in another plug-in already? If you find a bug,
21
perhaps someone else has already fixed it?
23
To answer these questions and more, take a moment to explore the
24
overall Bazaar Platform. Here are some links to browse:
26
* The Plugins page on the Wiki - http://bazaar-vcs.org/BzrPlugins
28
* The Bazaar product family on Launchpad - https://launchpad.net/bazaar
30
* Bug Tracker for the core product - https://bugs.launchpad.net/bzr/
32
* Blueprint Tracker for the core product - https://blueprints.launchpad.net/bzr/
34
If nothing else, perhaps you'll find inspiration in how other developers
35
have solved their challenges.
38
Planning and Discussing Changes
39
===============================
41
There is a very active community around Bazaar. Mostly we meet on IRC
42
(#bzr on irc.freenode.net) and on the mailing list. To join the Bazaar
43
community, see http://bazaar-vcs.org/BzrSupport.
45
If you are planning to make a change, it's a very good idea to mention it
46
on the IRC channel and/or on the mailing list. There are many advantages
47
to involving the community before you spend much time on a change.
50
* you get to build on the wisdom on others, saving time
52
* if others can direct you to similar code, it minimises the work to be done
54
* it assists everyone in coordinating direction, priorities and effort.
56
In summary, maximising the input from others typically minimises the
57
total effort required to get your changes merged. The community is
58
friendly, helpful and always keen to welcome newcomers.
61
Bazaar Development in a Nutshell
62
================================
64
Looking for a 10 minute introduction to submitting a change?
65
See http://bazaar-vcs.org/BzrGivingBack.
67
TODO: Merge that Wiki page into this document.
70
Understanding the Development Process
71
=====================================
73
The development team follows many best-practices including:
75
* a public roadmap and planning process in which anyone can participate
77
* time based milestones everyone can work towards and plan around
79
* extensive code review and feedback to contributors
81
* complete and rigorous test coverage on any code contributed
83
* automated validation that all tests still pass before code is merged
84
into the main code branch.
86
The key tools we use to enable these practices are:
88
* Launchpad - https://launchpad.net/
90
* Bazaar - http://bazaar-vcs.org/
92
* Bundle Buggy - http://bundlebuggy.aaronbentley.com/
94
* Patch Queue Manager - https://launchpad.net/pqm/
96
For further information, see http://bazaar-vcs.org/BzrDevelopment.
99
A Closer Look at the Merge & Review Process
100
===========================================
102
If you'd like to propose a change, please post to the
103
bazaar@lists.canonical.com list with a bundle, patch, or link to a
104
branch. Put '[PATCH]' or '[MERGE]' in the subject so Bundle Buggy
105
can pick it out, and explain the change in the email message text.
106
Remember to update the NEWS file as part of your change if it makes any
107
changes visible to users or plugin developers. Please include a diff
108
against mainline if you're giving a link to a branch.
110
You can generate a bundle like this::
112
bzr bundle > mybundle.patch
114
A .patch extension is recommended instead of .bundle as many mail clients
115
will send the latter as a binary file. If a bundle would be too long or your
116
mailer mangles whitespace (e.g. implicitly converts Unix newlines to DOS
117
newlines), use the merge-directive command instead like this::
119
bzr merge-directive http://bazaar-vcs.org http://example.org/my_branch > my_directive.patch
121
See the help for details on the arguments to merge-directive.
123
Please do **NOT** put [PATCH] or [MERGE] in the subject line if you don't
124
want it to be merged. If you want comments from developers rather than
125
to be merged, you can put '[RFC]' in the subject line.
127
Anyone is welcome to review code. There are broadly three gates for
130
* Doesn't reduce test coverage: if it adds new methods or commands,
131
there should be tests for them. There is a good test framework
132
and plenty of examples to crib from, but if you are having trouble
133
working out how to test something feel free to post a draft patch
136
* Doesn't reduce design clarity, such as by entangling objects
137
we're trying to separate. This is mostly something the more
138
experienced reviewers need to help check.
140
* Improves bugs, features, speed, or code simplicity.
142
Code that goes in should pass all three. The core developers take care
143
to keep the code quality high and understandable while recognising that
144
perfect is sometimes the enemy of good. (It is easy for reviews to make
145
people notice other things which should be fixed but those things should
146
not hold up the original fix being accepted. New things can easily be
147
recorded in the Bug Tracker instead.)
149
Anyone can "vote" on the mailing list. Core developers can also vote using
150
Bundle Buggy. Here are the voting codes and their explanations.
152
:approve: Reviewer wants this submission merged.
153
:tweak: Reviewer wants this submission merged with small changes. (No
155
:abstain: Reviewer does not intend to vote on this patch.
156
:resubmit: Please make changes and resubmit for review.
157
:reject: Reviewer doesn't want this kind of change merged.
158
:comment: Not really a vote. Reviewer just wants to comment, for now.
160
If a change gets two approvals from core reviewers, and no rejections,
161
then it's OK to come in. Any of the core developers can bring it into the
162
bzr.dev trunk and backport it to maintenance branches if required. The
163
Release Manager will merge the change into the branch for a pending
164
release, if any. As a guideline, core developers usually merge their own
165
changes and volunteer to merge other contributions if they were the second
166
reviewer to agree to a change.
168
To track the progress of proposed changes, use Bundle Buggy. See
169
http://bundlebuggy.aaronbentley.com/help for a link to all the
170
outstanding merge requests together with an explanation of the columns.
171
Bundle Buggy will also mail you a link to track just your change.
174
Preparing a Sandbox for Making Changes to Bazaar
175
================================================
177
Bazaar supports many ways of organising your work. See
178
http://bazaar-vcs.org/SharedRepositoryLayouts for a summary of the
179
popular alternatives.
181
Of course, the best choice for you will depend on numerous factors:
182
the number of changes you may be making, the complexity of the changes, etc.
183
As a starting suggestion though:
185
* create a local copy of the main development branch (bzr.dev) by using
188
bzr branch http://bazaar-vcs.org/bzr/bzr.dev/ bzr.dev
190
* keep your copy of bzr.dev prestine (by not developing in it) and keep
191
it up to date (by using bzr pull)
193
* create a new branch off your local bzr.dev copy for each issue
194
(bug or feature) you are working on.
196
This approach makes it easy to go back and make any required changes
197
after a code review. Resubmitting the change is then simple with no
198
risk of accidentially including edits related to other issues you may
199
be working on. After the changes for an issue are accepted and merged,
200
the associated branch can be deleted or archived as you wish.
203
Navigating the Code Base
204
========================
206
TODO: List and describe in one line the purpose of each directory
207
inside an installation of bzr.
209
TODO: Refer to a central location holding an up to date copy of the API
210
documentation generated by epydoc, e.g. something like
211
http://starship.python.net/crew/mwh/bzrlibapi/bzrlib.html.
217
The Importance of Testing
218
=========================
220
Reliability is a critical success factor for any Version Control System.
221
We want Bazaar to be highly reliable across multiple platforms while
222
evolving over time to meet the needs of its community.
224
In a nutshell, this is want we expect and encourage:
13
226
* New functionality should have test cases. Preferably write the
14
227
test before writing the code.
16
229
In general, you can test at either the command-line level or the
17
internal API level. See Writing Tests below for more detail.
230
internal API level. See Writing tests below for more detail.
19
* Try to practice Test-Driven Development. before fixing a bug, write a
232
* Try to practice Test-Driven Development: before fixing a bug, write a
20
233
test case so that it does not regress. Similarly for adding a new
21
234
feature: write a test case for a small version of the new feature before
22
235
starting on the code itself. Check the test fails on the old code, then
23
236
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.
238
By doing these things, the Bazaar team gets increased confidence that
239
changes do what they claim to do, whether provided by the core team or
240
by community members. Equally importantly, we can be surer that changes
241
down the track do not break new features or bug fixes that you are
244
As of May 2007, Bazaar ships with a test suite containing over 6000 tests
245
and growing. We are proud of it and want to remain so. As community
246
members, we all benefit from it. Would you trust version control on
247
your project to a product *without* a test suite like Bazaar has?
250
Running the Test Suite
251
======================
253
Currently, bzr selftest is used to invoke tests.
254
You can provide a pattern argument to run a subset. For example,
255
to run just the blackbox tests, run::
257
./bzr selftest -v blackbox
259
To skip a particular test (or set of tests), use the --exclude option
260
(shorthand -x) like so::
262
./bzr selftest -v -x blackbox
264
To ensure that all tests are being run and succeeding, you can use the
265
--strict option which will fail if there are any missing features or known
268
./bzr selftest --strict
270
To list tests without running them, use the --list-only option like so::
272
./bzr selftest --list-only
274
This option can be combined with other selftest options (like -x) and
275
filter patterns to understand their effect.
281
In general tests should be placed in a file named test_FOO.py where
282
FOO is the logical thing under test. That file should be placed in the
283
tests subdirectory under the package being tested.
285
For example, tests for merge3 in bzrlib belong in bzrlib/tests/test_merge3.py.
286
See bzrlib/tests/test_sampler.py for a template test script.
288
Tests can be written for the UI or for individual areas of the library.
289
Choose whichever is appropriate: if adding a new command, or a new command
290
option, then you should be writing a UI test. If you are both adding UI
291
functionality and library functionality, you will want to write tests for
292
both the UI and the core behaviours. We call UI tests 'blackbox' tests
293
and they are found in ``bzrlib/tests/blackbox/*.py``.
295
When writing blackbox tests please honour the following conventions:
297
1. Place the tests for the command 'name' in
298
bzrlib/tests/blackbox/test_name.py. This makes it easy for developers
299
to locate the test script for a faulty command.
301
2. Use the 'self.run_bzr("name")' utility function to invoke the command
302
rather than running bzr in a subprocess or invoking the
303
cmd_object.run() method directly. This is a lot faster than
304
subprocesses and generates the same logging output as running it in a
305
subprocess (which invoking the method directly does not).
307
3. Only test the one command in a single test script. Use the bzrlib
308
library when setting up tests and when evaluating the side-effects of
309
the command. We do this so that the library api has continual pressure
310
on it to be as functional as the command line in a simple manner, and
311
to isolate knock-on effects throughout the blackbox test suite when a
312
command changes its name or signature. Ideally only the tests for a
313
given command are affected when a given command is changed.
315
4. If you have a test which does actually require running bzr in a
316
subprocess you can use ``run_bzr_subprocess``. By default the spawned
317
process will not load plugins unless ``--allow-plugins`` is supplied.
323
We make selective use of doctests__. In general they should provide
324
*examples* within the API documentation which can incidentally be tested. We
325
don't try to test every important case using doctests -- regular Python
326
tests are generally a better solution.
328
Most of these are in ``bzrlib/doc/api``. More additions are welcome.
330
__ http://docs.python.org/lib/module-doctest.html
333
Skipping tests and test requirements
334
------------------------------------
336
In our enhancements to unittest we allow for some addition results beyond
337
just success or failure.
339
If a test can't be run, it can say that it's skipped. This is typically
340
used in parameterized tests - for example if a transport doesn't support
341
setting permissions, we'll skip the tests that relating to that. ::
344
return self.branch_format.initialize(repo.bzrdir)
345
except errors.UninitializableFormat:
346
raise tests.TestSkipped('Uninitializable branch format')
348
Raising TestSkipped is a good idea when you want to make it clear that the
349
test was not run, rather than just returning which makes it look as if it
352
Several different cases are distinguished:
355
Generic skip; the only type that was present up to bzr 0.18.
358
The test doesn't apply to the parameters with which it was run.
359
This is typically used when the test is being applied to all
360
implementations of an interface, but some aspects of the interface
361
are optional and not present in particular concrete
362
implementations. (Some tests that should raise this currently
363
either silently return or raise TestSkipped.) Another option is
364
to use more precise parameterization to avoid generating the test
368
**(Not implemented yet)**
369
The test can't be run because of an inherent limitation of the
370
environment, such as not having symlinks or not supporting
374
The test can't be run because a dependency (typically a Python
375
library) is not available in the test environment. These
376
are in general things that the person running the test could fix
377
by installing the library. It's OK if some of these occur when
378
an end user runs the tests or if we're specifically testing in a
379
limited environment, but a full test should never see them.
382
The test exists but is known to fail, for example because the
383
code to fix it hasn't been run yet. Raising this allows
384
you to distinguish these failures from the ones that are not
385
expected to fail. This could be conditionally raised if something
386
is broken on some platforms but not on others.
388
We plan to support three modes for running the test suite to control the
389
interpretation of these results. Strict mode is for use in situations
390
like merges to the mainline and releases where we want to make sure that
391
everything that can be tested has been tested. Lax mode is for use by
392
developers who want to temporarily tolerate some known failures. The
393
default behaviour is obtained by ``bzr selftest`` with no options, and
394
also (if possible) by running under another unittest harness.
396
======================= ======= ======= ========
397
result strict default lax
398
======================= ======= ======= ========
399
TestSkipped pass pass pass
400
TestNotApplicable pass pass pass
401
TestPlatformLimit pass pass pass
402
TestDependencyMissing fail pass pass
403
KnownFailure fail pass pass
404
======================= ======= ======= ========
407
Test feature dependencies
408
-------------------------
410
Rather than manually checking the environment in each test, a test class
411
can declare its dependence on some test features. The feature objects are
412
checked only once for each run of the whole test suite.
414
For historical reasons, as of May 2007 many cases that should depend on
415
features currently raise TestSkipped.)
419
class TestStrace(TestCaseWithTransport):
421
_test_needs_features = [StraceFeature]
423
This means all tests in this class need the feature. The feature itself
424
should provide a ``_probe`` method which is called once to determine if
427
These should generally be equivalent to either TestDependencyMissing or
428
sometimes TestPlatformLimit.
434
Known failures are when a test exists but we know it currently doesn't
435
work, allowing the test suite to still pass. These should be used with
436
care, we don't want a proliferation of quietly broken tests. It might be
437
appropriate to use them if you've committed a test for a bug but not the
438
fix for it, or if something works on Unix but not on Windows.
441
Testing exceptions and errors
442
-----------------------------
444
It's important to test handling of errors and exceptions. Because this
445
code is often not hit in ad-hoc testing it can often have hidden bugs --
446
it's particularly common to get NameError because the exception code
447
references a variable that has since been renamed.
449
.. TODO: Something about how to provoke errors in the right way?
451
In general we want to test errors at two levels:
453
1. A test in ``test_errors.py`` checking that when the exception object is
454
constructed with known parameters it produces an expected string form.
455
This guards against mistakes in writing the format string, or in the
456
``str`` representations of its parameters. There should be one for
457
each exception class.
459
2. Tests that when an api is called in a particular situation, it raises
460
an error of the expected class. You should typically use
461
``assertRaises``, which in the Bazaar test suite returns the exception
462
object to allow you to examine its parameters.
464
In some cases blackbox tests will also want to check error reporting. But
465
it can be difficult to provoke every error through the commandline
466
interface, so those tests are only done as needed -- eg in response to a
467
particular bug or if the error is reported in an unusual way(?) Blackbox
468
tests should mostly be testing how the command-line interface works, so
469
should only test errors if there is something particular to the cli in how
470
they're displayed or handled.
473
Interface implementation testing and test scenarios
474
---------------------------------------------------
476
There are several cases in Bazaar of multiple implementations of a common
477
conceptual interface. ("Conceptual" because
478
it's not necessary for all the implementations to share a base class,
479
though they often do.) Examples include transports and the working tree,
480
branch and repository classes.
482
In these cases we want to make sure that every implementation correctly
483
fulfils the interface requirements. For example, every Transport should
484
support the ``has()`` and ``get()`` and ``clone()`` methods. We have a
485
sub-suite of tests in ``test_transport_implementations``. (Most
486
per-implementation tests are in submodules of ``bzrlib.tests``, but not
487
the transport tests at the moment.)
489
These tests are repeated for each registered Transport, by generating a
490
new TestCase instance for the cross product of test methods and transport
491
implementations. As each test runs, it has ``transport_class`` and
492
``transport_server`` set to the class it should test. Most tests don't
493
access these directly, but rather use ``self.get_transport`` which returns
494
a transport of the appropriate type.
496
The goal is to run per-implementation only tests that relate to that
497
particular interface. Sometimes we discover a bug elsewhere that happens
498
with only one particular transport. Once it's isolated, we can consider
499
whether a test should be added for that particular implementation,
500
or for all implementations of the interface.
502
The multiplication of tests for different implementations is normally
503
accomplished by overriding the ``test_suite`` function used to load
504
tests from a module. This function typically loads all the tests,
505
then applies a TestProviderAdapter to them, which generates a longer
506
suite containing all the test variations.
512
Some utilities are provided for generating variations of tests. This can
513
be used for per-implementation tests, or other cases where the same test
514
code needs to run several times on different scenarios.
516
The general approach is to define a class that provides test methods,
517
which depend on attributes of the test object being pre-set with the
518
values to which the test should be applied. The test suite should then
519
also provide a list of scenarios in which to run the tests.
521
Typically ``multiply_tests_from_modules`` should be called from the test
522
module's ``test_suite`` function.
525
Essential Domain Classes
526
########################
528
Introducing the Object Model
529
============================
531
The core domain objects within the bazaar model are:
541
Transports are explained below. See http://bazaar-vcs.org/Classes/
542
for an introduction to the other key classes.
547
The ``Transport`` layer handles access to local or remote directories.
548
Each Transport object acts like a logical connection to a particular
549
directory, and it allows various operations on files within it. You can
550
*clone* a transport to get a new Transport connected to a subdirectory or
553
Transports are not used for access to the working tree. At present
554
working trees are always local and they are accessed through the regular
555
Python file io mechanisms.
560
Transports work in URLs. Take note that URLs are by definition only
561
ASCII - the decision of how to encode a Unicode string into a URL must be
562
taken at a higher level, typically in the Store. (Note that Stores also
563
escape filenames which cannot be safely stored on all filesystems, but
564
this is a different level.)
566
The main reason for this is that it's not possible to safely roundtrip a
567
URL into Unicode and then back into the same URL. The URL standard
568
gives a way to represent non-ASCII bytes in ASCII (as %-escapes), but
569
doesn't say how those bytes represent non-ASCII characters. (They're not
570
guaranteed to be UTF-8 -- that is common but doesn't happen everywhere.)
572
For example if the user enters the url ``http://example/%e0`` there's no
573
way to tell whether that character represents "latin small letter a with
574
grave" in iso-8859-1, or "latin small letter r with acute" in iso-8859-2
575
or malformed UTF-8. So we can't convert their URL to Unicode reliably.
577
Equally problematic if we're given a url-like string containing non-ascii
578
characters (such as the accented a) we can't be sure how to convert that
579
to the correct URL, because we don't know what encoding the server expects
580
for those characters. (Although this is not totally reliable we might still
581
accept these and assume they should be put into UTF-8.)
583
A similar edge case is that the url ``http://foo/sweet%2Fsour`` contains
584
one directory component whose name is "sweet/sour". The escaped slash is
585
not a directory separator. If we try to convert URLs to regular Unicode
586
paths this information will be lost.
588
This implies that Transports must natively deal with URLs; for simplicity
589
they *only* deal with URLs and conversion of other strings to URLs is done
590
elsewhere. Information they return, such as from ``list_dir``, is also in
591
the form of URL components.
51
600
We have a commitment to 6 months API stability - any supported symbol in a
52
601
release of bzr MUST NOT be altered in any way that would result in
67
616
details for you - such as updating the docstring, and issuing a warning
68
617
when the old api is used.
70
For unsupported API's, it does not hurt to follow this discipline, but its
619
For unsupported API's, it does not hurt to follow this discipline, but it's
71
620
not required. Minimally though, please try to rename things so that
72
621
callers will at least get an AttributeError rather than weird results.
75
Standard parameter types
76
------------------------
78
There are some common requirements in the library: some parameters need to be
79
unicode safe, some need byte strings, and so on. At the moment we have
80
only codified one specific pattern: Parameters that need to be unicode
81
should be check via 'bzrlib.osutils.safe_unicode'. This will coerce the
82
input into unicode in a consistent fashion, allowing trivial strings to be
83
used for programmer convenience, but not performing unpredictably in the
84
presence of different locales.
89
If you change the behaviour of a command, please update its docstring
90
in bzrlib/commands.py. This is displayed by the 'bzr help' command.
95
If you make a user-visible change, please add a note to the NEWS file.
96
The description should be written to make sense to someone who's just
97
a user of bzr, not a developer: new functions or classes shouldn't be
98
mentioned, but new commands, changes in behaviour or fixed nontrivial
99
bugs should be listed. See the existing entries for an idea of what
102
Within each release, entries in the news file should have the most
103
user-visible changes first. So the order should be approximately:
105
* changes to existing behaviour - the highest priority because the
106
user's existing knowledge is incorrect
107
* new features - should be brought to their attention
108
* bug fixes - may be of interest if the bug was affecting them, and
109
should include the bug number if any
110
* major documentation changes
111
* changes to internal interfaces
113
People who made significant contributions to each change are listed in
114
parenthesis. This can include reporting bugs (particularly with good
115
details or reproduction recipes), submitting patches, etc.
120
Functions, methods, classes and modules should have docstrings
121
describing how they are used.
123
The first line of the docstring should be a self-contained sentence.
125
For the special case of Command classes, this acts as the user-visible
126
documentation shown by the help command.
128
The docstrings should be formatted as reStructuredText_ (like this
129
document), suitable for processing using the epydoc_ tool into HTML
132
.. _reStructuredText: http://docutils.sourceforge.net/rst.html
133
.. _epydoc: http://epydoc.sourceforge.net/
624
Deprecation decorators
625
----------------------
627
``bzrlib.symbol_versioning`` provides decorators that can be attached to
628
methods, functions, and other interfaces to indicate that they should no
631
To deprecate a static method you must call ``deprecated_function``
632
(**not** method), after the staticmethod call::
635
@deprecated_function(zero_ninetyone)
636
def create_repository(base, shared=False, format=None):
638
When you deprecate an API, you should not just delete its tests, because
639
then we might introduce bugs in them. If the API is still present at all,
640
it should still work. The basic approach is to use
641
``TestCase.applyDeprecated`` which in one step checks that the API gives
642
the expected deprecation message, and also returns the real result from
643
the method, so that tests can keep running.
645
Coding Style Guidelines
646
=======================
140
651
Please write PEP-8__ compliant code.
653
__ http://www.python.org/peps/pep-0008.html
142
655
One often-missed requirement is that the first line of docstrings
143
656
should be a self-contained one-sentence summary.
145
__ http://www.python.org/peps/pep-0008.html
658
We use 4 space indents for blocks, and never use tab characters. (In vim,
661
Lines should be no more than 79 characters if at all possible.
662
Lines that continue a long statement may be indented in either of
665
within the parenthesis or other character that opens the block, e.g.::
671
or indented by four spaces::
677
The first is considered clearer by some people; however it can be a bit
678
harder to maintain (e.g. when the method name changes), and it does not
679
work well if the relevant parenthesis is already far to the right. Avoid
682
self.legbone.kneebone.shinbone.toebone.shake_it(one,
688
self.legbone.kneebone.shinbone.toebone.shake_it(one,
694
self.legbone.kneebone.shinbone.toebone.shake_it(
697
For long lists, we like to add a trailing comma and put the closing
698
character on the following line. This makes it easier to add new items in
701
from bzrlib.goo import (
707
There should be spaces between function paramaters, but not between the
708
keyword name and the value::
710
call(1, 3, cheese=quark)
714
;(defface my-invalid-face
715
; '((t (:background "Red" :underline t)))
716
; "Face used to highlight invalid constructs or other uglyties"
719
(defun my-python-mode-hook ()
720
;; setup preferred indentation style.
721
(setq fill-column 79)
722
(setq indent-tabs-mode nil) ; no tabs, never, I will not repeat
723
; (font-lock-add-keywords 'python-mode
724
; '(("^\\s *\t" . 'my-invalid-face) ; Leading tabs
725
; ("[ \t]+$" . 'my-invalid-face) ; Trailing spaces
726
; ("^[ \t]+$" . 'my-invalid-face)); Spaces only
730
(add-hook 'python-mode-hook 'my-python-mode-hook)
732
The lines beginning with ';' are comments. They can be activated
733
if one want to have a strong notice of some tab/space usage
740
* Imports should be done at the top-level of the file, unless there is
741
a strong reason to have them lazily loaded when a particular
742
function runs. Import statements have a cost, so try to make sure
743
they don't run inside hot functions.
745
* Module names should always be given fully-qualified,
746
i.e. ``bzrlib.hashcache`` not just ``hashcache``.
152
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.
752
Functions, methods or members that are "private" to bzrlib are given
753
a leading underscore prefix. Names without a leading underscore are
754
public not just across modules but to programmers using bzrlib as an
755
API. As a consequence, a leading underscore is appropriate for names
756
exposed across modules but that are not to be exposed to bzrlib API
156
759
We prefer class names to be concatenated capital words (``TestCase``)
157
760
and variables, methods and functions to be lowercase words joined by
304
1075
./bzr selftest -v blackbox
306
To skip a particular test (or set of tests), you need to use a negative
309
./bzr selftest '^(?!.*blackbox)'
312
Errors and exceptions
313
=====================
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.
1077
To skip a particular test (or set of tests), use the --exclude option
1078
(shorthand -x) like so::
1080
./bzr selftest -v -x blackbox
1082
To list tests without running them, use the --list-only option like so::
1084
./bzr selftest --list-only
1086
This option can be combined with other selftest options (like -x) and
1087
filter patterns to understand their effect.
1090
Handling Errors and Exceptions
1091
==============================
1093
Commands should return non-zero when they encounter circumstances that
1094
the user should really pay attention to - which includes trivial shell
1097
Recommended values are:
1100
1. Conflicts in merge-like operations, or changes are present in
1101
diff-like operations.
1102
2. Unrepresentable diff changes (i.e. binary files that we cannot show
1104
3. An error or exception has occurred.
1105
4. An internal error occurred (one that shows a traceback.)
1107
Errors are handled through Python exceptions. Exceptions should be defined
1108
inside bzrlib.errors, so that we can see the whole tree at a glance.
1110
We broadly classify errors as either being either internal or not,
1111
depending on whether ``internal_error`` is set or not. If we think it's our
1112
fault, we show a backtrace, an invitation to report the bug, and possibly
1113
other details. This is the default for errors that aren't specifically
1114
recognized as being caused by a user error. Otherwise we show a briefer
1115
message, unless -Derror was given.
1117
Many errors originate as "environmental errors" which are raised by Python
1118
or builtin libraries -- for example IOError. These are treated as being
1119
our fault, unless they're caught in a particular tight scope where we know
1120
that they indicate a user errors. For example if the repository format
1121
is not found, the user probably gave the wrong path or URL. But if one of
1122
the files inside the repository is not found, then it's our fault --
1123
either there's a bug in bzr, or something complicated has gone wrong in
1124
the environment that means one internal file was deleted.
1126
Many errors are defined in ``bzrlib/errors.py`` but it's OK for new errors
1127
to be added near the place where they are used.
1129
Exceptions are formatted for the user by conversion to a string
1130
(eventually calling their ``__str__`` method.) As a convenience the
1131
``._fmt`` member can be used as a template which will be mapped to the
1132
error's instance dict.
1134
New exception classes should be defined when callers might want to catch
1135
that exception specifically, or when it needs a substantially different
1138
Exception strings should start with a capital letter and should not have a
1139
final fullstop. If long, they may contain newlines to break the text.
1145
When you change bzrlib, please update the relevant documentation for the
1146
change you made: Changes to commands should update their help, and
1147
possibly end user tutorials; changes to the core library should be
1148
reflected in API documentation.
1153
If you make a user-visible change, please add a note to the NEWS file.
1154
The description should be written to make sense to someone who's just
1155
a user of bzr, not a developer: new functions or classes shouldn't be
1156
mentioned, but new commands, changes in behaviour or fixed nontrivial
1157
bugs should be listed. See the existing entries for an idea of what
1160
Within each release, entries in the news file should have the most
1161
user-visible changes first. So the order should be approximately:
1163
* changes to existing behaviour - the highest priority because the
1164
user's existing knowledge is incorrect
1165
* new features - should be brought to their attention
1166
* bug fixes - may be of interest if the bug was affecting them, and
1167
should include the bug number if any
1168
* major documentation changes
1169
* changes to internal interfaces
1171
People who made significant contributions to each change are listed in
1172
parenthesis. This can include reporting bugs (particularly with good
1173
details or reproduction recipes), submitting patches, etc.
1178
The docstring of a command is used by ``bzr help`` to generate help output
1179
for the command. The list 'takes_options' attribute on a command is used by
1180
``bzr help`` to document the options for the command - the command
1181
docstring does not need to document them. Finally, the '_see_also'
1182
attribute on a command can be used to reference other related help topics.
1187
Functions, methods, classes and modules should have docstrings
1188
describing how they are used.
1190
The first line of the docstring should be a self-contained sentence.
1192
For the special case of Command classes, this acts as the user-visible
1193
documentation shown by the help command.
1195
The docstrings should be formatted as reStructuredText_ (like this
1196
document), suitable for processing using the epydoc_ tool into HTML
1199
.. _reStructuredText: http://docutils.sourceforge.net/rst.html
1200
.. _epydoc: http://epydoc.sourceforge.net/
1209
The copyright policy for bzr was recently made clear in this email (edited
1210
for grammatical correctness)::
1212
The attached patch cleans up the copyright and license statements in
1213
the bzr source. It also adds tests to help us remember to add them
1214
with the correct text.
1216
We had the problem that lots of our files were "Copyright Canonical
1217
Development Ltd" which is not a real company, and some other variations
1218
on this theme. Also, some files were missing the GPL statements.
1220
I want to be clear about the intent of this patch, since copyright can
1221
be a little controversial.
1223
1) The big motivation for this is not to shut out the community, but
1224
just to clean up all of the invalid copyright statements.
1226
2) It has been the general policy for bzr that we want a single
1227
copyright holder for all of the core code. This is following the model
1228
set by the FSF, which makes it easier to update the code to a new
1229
license in case problems are encountered. (For example, if we want to
1230
upgrade the project universally to GPL v3 it is much simpler if there is
1231
a single copyright holder). It also makes it clearer if copyright is
1232
ever debated, there is a single holder, which makes it easier to defend
1233
in court, etc. (I think the FSF position is that if you assign them
1234
copyright, they can defend it in court rather than you needing to, and
1235
I'm sure Canonical would do the same).
1236
As such, Canonical has requested copyright assignments from all of the
1239
3) If someone wants to add code and not attribute it to Canonical, there
1240
is a specific list of files that are excluded from this check. And the
1241
test failure indicates where that is, and how to update it.
1243
4) If anyone feels that I changed a copyright statement incorrectly, just
1244
let me know, and I'll be happy to correct it. Whenever you have large
1245
mechanical changes like this, it is possible to make some mistakes.
1247
Just to reiterate, this is a community project, and it is meant to stay
1248
that way. Core bzr code is copyright Canonical for legal reasons, and
1249
the tests are just there to help us maintain that.
1252
Miscellaneous Topics
1253
####################
1258
Bazaar has a few facilities to help debug problems by going into pdb_, the
1261
.. _pdb: http://docs.python.org/lib/debugger-commands.html
1263
If the ``BZR_PDB`` environment variable is set
1264
then bzr will go into pdb post-mortem mode when an unhandled exception
1267
If you send a SIGQUIT signal to bzr, which can be done by pressing
1268
Ctrl-\\ on Unix, bzr will go into the debugger immediately. You can
1269
continue execution by typing ``c``. This can be disabled if necessary
1270
by setting the environment variable ``BZR_SIGQUIT_PDB=0``.
432
1334
valid characters are generated where possible.
438
If you'd like to propose a change, please post to the
439
bazaar-ng@lists.canonical.com list with a patch, bzr changeset, or link to a
440
branch. Please put '[patch]' in the subject so we can pick them out, and
441
include some text explaining the change. Remember to put an update to the NEWS
442
file in your diff, if it makes any changes visible to users or plugin
443
developers. Please include a diff against mainline if you're giving a link to
446
Please indicate if you think the code is ready to merge, or if it's just a
447
draft or for discussion. If you want comments from many developers rather than
448
to be merged, you can put '[rfc]' in the subject lines.
450
Anyone is welcome to review code. There are broadly three gates for
453
* Doesn't reduce test coverage: if it adds new methods or commands,
454
there should be tests for them. There is a good test framework
455
and plenty of examples to crib from, but if you are having trouble
456
working out how to test something feel free to post a draft patch
459
* Doesn't reduce design clarity, such as by entangling objects
460
we're trying to separate. This is mostly something the more
461
experienced reviewers need to help check.
463
* Improves bugs, features, speed, or code simplicity.
465
Code that goes in should pass all three.
467
If you read a patch please reply and say so. We can use a numeric scale
468
of -1, -0, +0, +1, meaning respectively "really don't want it in current
469
form", "somewhat uncomfortable", "ok with me", and "please put it in".
470
Anyone can "vote". (It's not really voting, just a terse expression.)
472
If something gets say two +1 votes from core reviewers, and no
473
vetos, then it's OK to come in. Any of the core developers can bring it
474
into their integration branch, which I'll merge regularly. (If you do
475
so, please reply and say so.)
478
Making installers for OS Windows
1340
The ``bzrlib.osutils`` module has many useful helper functions, including
1341
some more portable variants of functions in the standard library.
1343
In particular, don't use ``shutil.rmtree`` unless it's acceptable for it
1344
to fail on Windows if some files are readonly or still open elsewhere.
1345
Use ``bzrlib.osutils.rmtree`` instead.
1351
We write some extensions in C using pyrex. We design these to work in
1354
* User with no C compiler
1355
* User with C compiler
1358
The recommended way to install bzr is to have a C compiler so that the
1359
extensions can be built, but if no C compiler is present, the pure python
1360
versions we supply will work, though more slowly.
1362
For developers we recommend that pyrex be installed, so that the C
1363
extensions can be changed if needed.
1365
For the C extensions, the extension module should always match the
1366
original python one in all respects (modulo speed). This should be
1367
maintained over time.
1369
To create an extension, add rules to setup.py for building it with pyrex,
1370
and with distutils. Now start with an empty .pyx file. At the top add
1371
"include 'yourmodule.py'". This will import the contents of foo.py into this
1372
file at build time - remember that only one module will be loaded at
1373
runtime. Now you can subclass classes, or replace functions, and only your
1374
changes need to be present in the .pyx file.
1376
Note that pyrex does not support all 2.4 programming idioms, so some
1377
syntax changes may be required. I.e.
1379
- 'from foo import (bar, gam)' needs to change to not use the brackets.
1380
- 'import foo.bar as bar' needs to be 'import foo.bar; bar = foo.bar'
1382
If the changes are too dramatic, consider
1383
maintaining the python code twice - once in the .pyx, and once in the .py,
1384
and no longer including the .py file.
1387
Making Installers for OS Windows
479
1388
================================
480
1389
To build a win32 installer, see the instructions on the wiki page:
481
1390
http://bazaar-vcs.org/BzrWin32Installer
484
:: vim: ft=rst tw=74 ai
1393
Core Developer Tasks
1394
####################
1399
What is a Core Developer?
1400
-------------------------
1402
While everyone in the Bazaar community is welcome and encouraged to
1403
propose and submit changes, a smaller team is reponsible for pulling those
1404
changes together into a cohesive whole. In addition to the general developer
1405
stuff covered above, "core" developers have responsibility for:
1408
* reviewing blueprints
1410
* managing releases.
1413
Removing barriers to community participation is a key reason for adopting
1414
distributed VCS technology. While DVCS removes many technical barriers,
1415
a small number of social barriers are often necessary instead.
1416
By documenting how the above things are done, we hope to
1417
encourage more people to participate in these activities, keeping the
1418
differences between core and non-core contributors to a minimum.
1421
The Development Lifecycle
1422
-------------------------
1424
As a rule, Bazaar development follows a 4 week cycle:
1426
* 2 weeks - general changes
1427
* 1 week - feature freeze
1428
* 1 week+ - Release Candidate stabilization
1430
During the FeatureFreeze week, the trunk (bzr.dev) is open in a limited
1431
way: only low risk changes, critical and high priority fixes are accepted
1432
during this time. At the end of FeatureFreeze, a branch is created for the
1433
first Release Candidate and the trunk is reopened for general development
1434
on the *next* release. A week or so later, the final release is packaged
1435
assuming no serious problems were encountered with the one or more Release
1439
There is a one week overlap between the start of one release and
1440
the end of the previous one.
1443
Communicating and Coordinating
1444
------------------------------
1446
While it has many advantages, one of the challenges of distributed
1447
development is keeping everyone else aware of what you're working on.
1448
There are numerous ways to do this:
1450
#. Assign bugs to yourself in Launchpad
1451
#. Mention it on the mailing list
1452
#. Mention it on IRC
1454
As well as the email notifcations that occur when merge requests are sent
1455
and reviewed, you can keep others informed of where you're spending your
1456
energy by emailing the **bazaar-commits** list implicitly. To do this,
1457
install and configure the Email plugin. One way to do this is add these
1458
configuration settings to your central configuration file (e.g.
1459
``~/.bazaar/bazaar.conf`` on Linux)::
1462
email = Joe Smith <joe.smith@internode.on.net>
1463
smtp_server = mail.internode.on.net:25
1465
Then add these lines for the relevant branches in ``locations.conf``::
1467
post_commit_to = bazaar-commits@lists.canonical.com
1468
post_commit_mailer = smtplib
1470
While attending a sprint, RobertCollins' Dbus plugin is useful for the
1471
same reason. See the documentation within the plugin for information on
1472
how to set it up and configure it.
1478
Setting Up Your Workspace for Reviews
1479
-------------------------------------
1481
TODO: Incorporate John Arbash Meinel's detailed email to Ian C on the
1482
numerous ways of setting up integration branches.
1485
The Review Checklist
1486
--------------------
1488
See `A Closer Look at the Merge & Review Process`_
1489
for information on the gates used to decide whether code can be merged
1490
or not and details on how review results are recorded and communicated.
1493
The Importance of Timely Reviews
1494
--------------------------------
1496
Good reviews do take time. They also regularly require a solid
1497
understanding of the overall code base. In practice, this means a small
1498
number of people often have a large review burden - with knowledge comes
1499
responsibility. No one like their merge requests sitting in a queue going
1500
nowhere, so reviewing sooner rather than later is strongly encouraged.
1509
Of the many workflows supported by Bazaar, the one adopted for Bazaar
1510
development itself is known as "Decentralized with automatic gatekeeper".
1511
To repeat the explanation of this given on
1512
http://bazaar-vcs.org/Workflows:
1515
In this workflow, each developer has their own branch or
1516
branches, plus read-only access to the mainline. A software gatekeeper
1517
(e.g. PQM) has commit rights to the main branch. When a developer wants
1518
their work merged, they request the gatekeeper to merge it. The gatekeeper
1519
does a merge, a compile, and runs the test suite. If the code passes, it
1520
is merged into the mainline.
1522
In a nutshell, here's the overall submission process:
1524
#. get your work ready (including review except for trivial changes)
1525
#. push to a public location
1526
#. ask PQM to merge from that location
1529
At present, PQM always takes the changes to merge from a branch
1530
at a URL that can be read by it. For Bazaar, that means a public,
1531
typically http, URL.
1533
As a result, the following things are needed to use PQM for submissions:
1535
#. A publicly available web server
1536
#. Your OpenPGP key registered with PQM (contact RobertCollins for this)
1537
#. The PQM plugin installed and configured (not strictly required but
1538
highly recommended).
1541
Selecting a Public Branch Location
1542
----------------------------------
1544
If you don't have your own web server running, branches can always be
1545
pushed to Launchpad. Here's the process for doing that:
1547
Depending on your location throughout the world and the size of your
1548
repository though, it is often quicker to use an alternative public
1549
location to Launchpad, particularly if you can set up your own repo and
1550
push into that. By using an existing repo, push only needs to send the
1551
changes, instead of the complete repository every time. Note that it is
1552
easy to register branches in other locations with Launchpad so no benefits
1553
are lost by going this way.
1556
For Canonical staff, http://people.ubuntu.com/~<user>/ is one
1557
suggestion for public http branches. Contact your manager for information
1558
on accessing this system if required.
1560
It should also be noted that best practice in this area is subject to
1561
change as things evolve. For example, once the Bazaar smart server on
1562
Launchpad supports server-side branching, the performance situation will
1563
be very different to what it is now (Jun 2007).
1566
Configuring the PQM Plug-In
1567
---------------------------
1569
While not strictly required, the PQM plugin automates a few things and
1570
reduces the chance of error. Before looking at the plugin, it helps to
1571
understand a little more how PQM operates. Basically, PQM requires an
1572
email indicating what you want it to do. The email typically looks like
1575
star-merge source-branch target-branch
1579
star-merge http://bzr.arbash-meinel.com/branches/bzr/jam-integration http://bazaar-vcs.org/bzr/bzr.dev
1581
Note that the command needs to be on one line. The subject of the email
1582
will be used for the commit message. The email also needs to be ``gpg``
1583
signed with a key that PQM accepts.
1585
The advantages of using the PQM plugin are:
1587
#. You can use the config policies to make it easy to set up public
1588
branches, so you don't have to ever type the full paths you want to merge
1591
#. It checks to make sure the public branch last revision matches the
1592
local last revision so you are submitting what you think you are.
1594
#. It uses the same public_branch and smtp sending settings as bzr-email,
1595
so if you have one set up, you have the other mostly set up.
1597
#. Thunderbird refuses to not wrap lines, and request lines are usually
1598
pretty long (you have 2 long URLs in there).
1600
Here are sample configuration settings for the PQM plugin. Here are the
1601
lines in bazaar.conf::
1604
email = Joe Smith <joe.smith@internode.on.net>
1605
smtp_server=mail.internode.on.net:25
1607
And here are the lines in ``locations.conf`` (or ``branch.conf`` for
1608
dirstate-tags branches)::
1610
[/home/joe/bzr/my-integration]
1611
push_location = sftp://joe-smith@bazaar.launchpad.net/%7Ejoe-smith/bzr/my-integration/
1612
push_location:policy = norecurse
1613
public_branch = http://bazaar.launchpad.net/~joe-smith/bzr/my-integration/
1614
public_branch:policy = appendpath
1615
pqm_email = Bazaar PQM <pqm@bazaar-vcs.org>
1616
pqm_branch = http://bazaar-vcs.org/bzr/bzr.dev
1618
Note that the push settings will be added by the first ``push`` on
1619
a branch. Indeed the preferred way to generate the lines above is to use
1620
``push`` with an argument, then copy-and-paste the other lines into
1627
Here is one possible recipe once the above environment is set up:
1629
#. pull bzr.dev => my-integration
1630
#. merge patch => my-integration
1631
#. fix up any final merge conflicts (NEWS being the big killer here).
1637
The ``push`` step is not required if ``my-integration`` is a checkout of
1640
Because of defaults, you can type a single message into commit and
1641
pqm-commit will reuse that.
1644
Tracking Change Acceptance
1645
--------------------------
1647
The web interface to PQM is https://pqm.bazaar-vcs.org/. After submitting
1648
a change, you can visit this URL to confirm it was received and placed in
1651
When PQM completes processing a change, an email is sent to you with the
1655
Reviewing Blueprints
1656
====================
1658
Blueprint Tracking Using Launchpad
1659
----------------------------------
1661
New features typically require a fair amount of discussion, design and
1662
debate. For Bazaar, that information is often captured in a so-called
1663
"blueprint" on our Wiki. Overall tracking of blueprints and their status
1664
is done using Launchpad's relevant tracker,
1665
https://blueprints.launchpad.net/bzr/. Once a blueprint for ready for
1666
review, please announce it on the mailing list.
1668
Alternatively, send an email begining with [RFC] with the proposal to the
1669
list. In some cases, you may wish to attach proposed code or a proposed
1670
developer document if that best communicates the idea. Debate can then
1671
proceed using the normal merge review processes.
1674
Recording Blueprint Review Feedback
1675
-----------------------------------
1677
Unlike its Bug Tracker, Launchpad's Blueprint Tracker doesn't currently
1678
(Jun 2007) support a chronological list of comment responses. Review
1679
feedback can either be recorded on the Wiki hosting the blueprints or by
1680
using Launchpad's whiteboard feature.
1689
As the two senior developers, Martin Pool and Robert Collins coordinate
1690
the overall Bazaar product development roadmap. Core developers provide
1691
input and review into this, particularly during sprints. It's totally
1692
expected that community members ought to be working on things that
1693
interest them the most. The roadmap is valuable though because it provides
1694
context for understanding where the product is going as a whole and why.
1697
Using Releases and Milestones in Launchpad
1698
------------------------------------------
1700
TODO ... (Exact policies still under discussion)
1706
Keeping on top of bugs reported is an important part of ongoing release
1707
planning. Everyone in the community is welcome and encouraged to raise
1708
bugs, confirm bugs raised by others, and nominate a priority. Practically
1709
though, a good percentage of bug triage is often done by the core
1710
developers, partially because of their depth of product knowledge.
1712
With respect to bug triage, core developers are encouraged to play an
1713
active role with particular attention to the following tasks:
1715
* keeping the number of unconfirmed bugs low
1716
* ensuring the priorities are generally right (everything as critical - or
1717
medium - is meaningless)
1718
* looking out for regressions and turning those around sooner rather than later.
1721
As well as prioritizing bugs and nominating them against a
1722
target milestone, Launchpad lets core developers offer to mentor others in
1732
TODO: Things to cover:
1734
* RFI on release objectives
1735
* RFI on higher risk things that are best done early, e.g. changes to file
1737
* Communication of proposed dates
1740
Weekly Status Updates
1741
---------------------
1743
TODO: Things to cover:
1745
* Early communication to downstream teams (e.g. Launchpad) about changes in dependencies.
1746
* Reminder re lifecycle and where we're up to right now
1747
* Summary of recent successes and pending work
1748
* Reminder re release objectives
1749
* Reminder re things needing attention, e.g. bug triage, reviews, testing of certain things, etc.
1755
TODO: Get material from http://bazaar-vcs.org/FeatureFreeze.
1761
TODO: Get material from http://bazaar-vcs.org/ReleaseChecklist and clean
1762
it up to make it clearer what the RC vs final vs both tasks are.
1768
TODO: Get material from http://bazaar-vcs.org/ReleaseChecklist and clean
1769
it up to make it clearer what the RC vs final vs both tasks are.
1772
vim: ft=rst tw=74 ai
added
removed
doc/developers/HACKING.txt
