73
70
Bazaar Development in a Nutshell
74
71
================================
76
.. was from http://wiki.bazaar.canonical.com/BzrGivingBack
78
One of the fun things about working on a version control system like Bazaar is
79
that the users have a high level of proficiency in contributing back into
80
the tool. Consider the following very brief introduction to contributing back
81
to Bazaar. More detailed instructions are in the following sections.
86
First, get a local copy of the development mainline (See `Why make a local
92
$ bzr branch lp:bzr bzr.dev
94
Now make your own branch::
96
$ bzr branch bzr.dev 123456-my-bugfix
98
This will give you a branch called "123456-my-bugfix" that you can work on
99
and commit in. Here, you can study the code, make a fix or a new feature.
100
Feel free to commit early and often (after all, it's your branch!).
102
Documentation improvements are an easy place to get started giving back to the
103
Bazaar project. The documentation is in the `doc/` subdirectory of the Bazaar
106
When you are done, make sure that you commit your last set of changes as well!
107
Once you are happy with your changes, ask for them to be merged, as described
110
Making a Merge Proposal
111
-----------------------
113
The Bazaar developers use Launchpad to further enable a truly distributed
114
style of development. Anyone can propose a branch for merging into the Bazaar
115
trunk. To start this process, you need to push your branch to Launchpad. To
116
do this, you will need a Launchpad account and user name, e.g.
117
`your_lp_username`. You can push your branch to Launchpad directly from
120
$ bzr push lp:~your_lp_username/bzr/meaningful_name_here
122
After you have pushed your branch, you will need to propose it for merging to
123
the Bazaar trunk. Go to
124
<https://launchpad.net/your_lp_username/bzr/meaningful_name_here> and choose
125
"Propose for merging into another branch". Select "~bzr/bzr/trunk" to hand
126
your changes off to the Bazaar developers for review and merging.
128
Alternatively, after pushing you can use the ``lp-propose`` command to
129
create the merge proposal.
131
Using a meaningful name for your branch will help you and the reviewer(s)
132
better track the submission. Use a very succint description of your submission
133
and prefix it with bug number if needed (lp:~mbp/bzr/484558-merge-directory
134
for example). Alternatively, you can suffix with the bug number
135
(lp:~jameinel/bzr/export-file-511987).
141
Please put a "cover letter" on your merge request explaining:
143
* the reason **why** you're making this change
145
* **how** this change achieves this purpose
147
* anything else you may have fixed in passing
149
* anything significant that you thought of doing, such as a more
150
extensive fix or a different approach, but didn't or couldn't do now
152
A good cover letter makes reviewers' lives easier because they can decide
153
from the letter whether they agree with the purpose and approach, and then
154
assess whether the patch actually does what the cover letter says.
155
Explaining any "drive-by fixes" or roads not taken may also avoid queries
156
from the reviewer. All in all this should give faster and better reviews.
157
Sometimes writing the cover letter helps the submitter realize something
158
else they need to do. The size of the cover letter should be proportional
159
to the size and complexity of the patch.
162
Why make a local copy of bzr.dev?
163
---------------------------------
165
Making a local mirror of bzr.dev is not strictly necessary, but it means
167
- You can use that copy of bzr.dev as your main bzr executable, and keep it
168
up-to-date using ``bzr pull``.
169
- Certain operations are faster, and can be done when offline. For example:
172
- ``bzr diff -r ancestor:...``
175
- When it's time to create your next branch, it's more convenient. When you
176
have further contributions to make, you should do them in their own branch::
179
$ bzr branch bzr.dev additional_fixes
180
$ cd additional_fixes # hack, hack, hack
73
Looking for a 10 minute introduction to submitting a change?
74
See http://bazaar-vcs.org/BzrGivingBack.
76
TODO: Merge that Wiki page into this document.
184
79
Understanding the Development Process
185
80
=====================================
187
The development team follows many practices including:
82
The development team follows many best-practices including:
189
84
* a public roadmap and planning process in which anyone can participate
202
97
* Launchpad - https://launchpad.net/
204
* Bazaar - http://bazaar.canonical.com/
99
* Bazaar - http://bazaar-vcs.org/
101
* Bundle Buggy - http://bundlebuggy.aaronbentley.com/
206
103
* Patch Queue Manager - https://launchpad.net/pqm/
208
For further information, see <http://wiki.bazaar.canonical.com/BzrDevelopment>.
105
For further information, see http://bazaar-vcs.org/BzrDevelopment.
108
A Closer Look at the Merge & Review Process
109
===========================================
111
If you'd like to propose a change, please post to the
112
bazaar@lists.canonical.com list with a bundle, patch, or link to a
113
branch. Put '[PATCH]' or '[MERGE]' in the subject so Bundle Buggy
114
can pick it out, and explain the change in the email message text.
115
Remember to update the NEWS file as part of your change if it makes any
116
changes visible to users or plugin developers. Please include a diff
117
against mainline if you're giving a link to a branch.
119
You can generate a bundle like this::
121
bzr bundle > mybundle.patch
123
A .patch extension is recommended instead of .bundle as many mail clients
124
will send the latter as a binary file. If a bundle would be too long or your
125
mailer mangles whitespace (e.g. implicitly converts Unix newlines to DOS
126
newlines), use the merge-directive command instead like this::
128
bzr merge-directive http://bazaar-vcs.org http://example.org/my_branch > my_directive.patch
130
See the help for details on the arguments to merge-directive.
132
Please do **NOT** put [PATCH] or [MERGE] in the subject line if you don't
133
want it to be merged. If you want comments from developers rather than
134
to be merged, you can put '[RFC]' in the subject line.
136
Anyone is welcome to review code. There are broadly three gates for
139
* Doesn't reduce test coverage: if it adds new methods or commands,
140
there should be tests for them. There is a good test framework
141
and plenty of examples to crib from, but if you are having trouble
142
working out how to test something feel free to post a draft patch
145
* Doesn't reduce design clarity, such as by entangling objects
146
we're trying to separate. This is mostly something the more
147
experienced reviewers need to help check.
149
* Improves bugs, features, speed, or code simplicity.
151
Code that goes in should pass all three. The core developers take care
152
to keep the code quality high and understandable while recognising that
153
perfect is sometimes the enemy of good. (It is easy for reviews to make
154
people notice other things which should be fixed but those things should
155
not hold up the original fix being accepted. New things can easily be
156
recorded in the Bug Tracker instead.)
158
Anyone can "vote" on the mailing list. Core developers can also vote using
159
Bundle Buggy. Here are the voting codes and their explanations.
161
:approve: Reviewer wants this submission merged.
162
:tweak: Reviewer wants this submission merged with small changes. (No
164
:abstain: Reviewer does not intend to vote on this patch.
165
:resubmit: Please make changes and resubmit for review.
166
:reject: Reviewer doesn't want this kind of change merged.
167
:comment: Not really a vote. Reviewer just wants to comment, for now.
169
If a change gets two approvals from core reviewers, and no rejections,
170
then it's OK to come in. Any of the core developers can bring it into the
171
bzr.dev trunk and backport it to maintenance branches if required. The
172
Release Manager will merge the change into the branch for a pending
173
release, if any. As a guideline, core developers usually merge their own
174
changes and volunteer to merge other contributions if they were the second
175
reviewer to agree to a change.
177
To track the progress of proposed changes, use Bundle Buggy. See
178
http://bundlebuggy.aaronbentley.com/help for a link to all the
179
outstanding merge requests together with an explanation of the columns.
180
Bundle Buggy will also mail you a link to track just your change.
213
183
Preparing a Sandbox for Making Changes to Bazaar
214
184
================================================
216
186
Bazaar supports many ways of organising your work. See
217
http://wiki.bazaar.canonical.com/SharedRepositoryLayouts for a summary of the
187
http://bazaar-vcs.org/SharedRepositoryLayouts for a summary of the
218
188
popular alternatives.
220
190
Of course, the best choice for you will depend on numerous factors:
242
212
Navigating the Code Base
243
213
========================
245
.. Was at <http://wiki.bazaar.canonical.com/NewDeveloperIntroduction>
247
Some of the key files in this directory are:
250
The command you run to start Bazaar itself. This script is pretty
251
short and just does some checks then jumps into bzrlib.
254
This file covers a brief introduction to Bazaar and lists some of its
258
Summary of changes in each Bazaar release that can affect users or
262
Installs Bazaar system-wide or to your home directory. To perform
263
development work on Bazaar it is not required to run this file - you
264
can simply run the bzr command from the top level directory of your
265
development copy. Note: That if you run setup.py this will create a
266
'build' directory in your development branch. There's nothing wrong
267
with this but don't be confused by it. The build process puts a copy
268
of the main code base into this build directory, along with some other
269
files. You don't need to go in here for anything discussed in this
273
Possibly the most exciting folder of all, bzrlib holds the main code
274
base. This is where you will go to edit python files and contribute to
278
Holds documentation on a whole range of things on Bazaar from the
279
origination of ideas within the project to information on Bazaar
280
features and use cases. Within this directory there is a subdirectory
281
for each translation into a human language. All the documentation
282
is in the ReStructuredText markup language.
285
Documentation specifically targeted at Bazaar and plugin developers.
286
(Including this document.)
290
Automatically-generated API reference information is available at
291
<http://starship.python.net/crew/mwh/bzrlibapi/>.
293
See also the `Bazaar Architectural Overview
294
<http://doc.bazaar.canonical.com/developers/overview.html>`_.
215
TODO: List and describe in one line the purpose of each directory
216
inside an installation of bzr.
218
TODO: Refer to a central location holding an up to date copy of the API
219
documentation generated by epydoc, e.g. something like
220
http://starship.python.net/crew/mwh/bzrlibapi/bzrlib.html.
226
The Importance of Testing
227
=========================
229
Reliability is a critical success factor for any Version Control System.
230
We want Bazaar to be highly reliable across multiple platforms while
231
evolving over time to meet the needs of its community.
233
In a nutshell, this is want we expect and encourage:
235
* New functionality should have test cases. Preferably write the
236
test before writing the code.
238
In general, you can test at either the command-line level or the
239
internal API level. See Writing tests below for more detail.
241
* Try to practice Test-Driven Development: before fixing a bug, write a
242
test case so that it does not regress. Similarly for adding a new
243
feature: write a test case for a small version of the new feature before
244
starting on the code itself. Check the test fails on the old code, then
245
add the feature or fix and check it passes.
247
By doing these things, the Bazaar team gets increased confidence that
248
changes do what they claim to do, whether provided by the core team or
249
by community members. Equally importantly, we can be surer that changes
250
down the track do not break new features or bug fixes that you are
253
As of May 2007, Bazaar ships with a test suite containing over 6000 tests
254
and growing. We are proud of it and want to remain so. As community
255
members, we all benefit from it. Would you trust version control on
256
your project to a product *without* a test suite like Bazaar has?
259
Running the Test Suite
260
======================
262
Currently, bzr selftest is used to invoke tests.
263
You can provide a pattern argument to run a subset. For example,
264
to run just the blackbox tests, run::
266
./bzr selftest -v blackbox
268
To skip a particular test (or set of tests), use the --exclude option
269
(shorthand -x) like so::
271
./bzr selftest -v -x blackbox
273
To ensure that all tests are being run and succeeding, you can use the
274
--strict option which will fail if there are any missing features or known
277
./bzr selftest --strict
279
To list tests without running them, use the --list-only option like so::
281
./bzr selftest --list-only
283
This option can be combined with other selftest options (like -x) and
284
filter patterns to understand their effect.
287
Test suite debug flags
288
----------------------
290
Similar to the global ``-Dfoo`` debug options, bzr selftest accepts
291
``-E=foo`` debug flags. These flags are:
293
:allow_debug: do *not* clear the global debug flags when running a test.
294
This can provide useful logging to help debug test failures when used
295
with e.g. ``bzr -Dhpss selftest -E=allow_debug``
301
In general tests should be placed in a file named test_FOO.py where
302
FOO is the logical thing under test. That file should be placed in the
303
tests subdirectory under the package being tested.
305
For example, tests for merge3 in bzrlib belong in bzrlib/tests/test_merge3.py.
306
See bzrlib/tests/test_sampler.py for a template test script.
308
Tests can be written for the UI or for individual areas of the library.
309
Choose whichever is appropriate: if adding a new command, or a new command
310
option, then you should be writing a UI test. If you are both adding UI
311
functionality and library functionality, you will want to write tests for
312
both the UI and the core behaviours. We call UI tests 'blackbox' tests
313
and they are found in ``bzrlib/tests/blackbox/*.py``.
315
When writing blackbox tests please honour the following conventions:
317
1. Place the tests for the command 'name' in
318
bzrlib/tests/blackbox/test_name.py. This makes it easy for developers
319
to locate the test script for a faulty command.
321
2. Use the 'self.run_bzr("name")' utility function to invoke the command
322
rather than running bzr in a subprocess or invoking the
323
cmd_object.run() method directly. This is a lot faster than
324
subprocesses and generates the same logging output as running it in a
325
subprocess (which invoking the method directly does not).
327
3. Only test the one command in a single test script. Use the bzrlib
328
library when setting up tests and when evaluating the side-effects of
329
the command. We do this so that the library api has continual pressure
330
on it to be as functional as the command line in a simple manner, and
331
to isolate knock-on effects throughout the blackbox test suite when a
332
command changes its name or signature. Ideally only the tests for a
333
given command are affected when a given command is changed.
335
4. If you have a test which does actually require running bzr in a
336
subprocess you can use ``run_bzr_subprocess``. By default the spawned
337
process will not load plugins unless ``--allow-plugins`` is supplied.
343
We make selective use of doctests__. In general they should provide
344
*examples* within the API documentation which can incidentally be tested. We
345
don't try to test every important case using doctests -- regular Python
346
tests are generally a better solution.
348
Most of these are in ``bzrlib/doc/api``. More additions are welcome.
350
__ http://docs.python.org/lib/module-doctest.html
353
Skipping tests and test requirements
354
------------------------------------
356
In our enhancements to unittest we allow for some addition results beyond
357
just success or failure.
359
If a test can't be run, it can say that it's skipped. This is typically
360
used in parameterized tests - for example if a transport doesn't support
361
setting permissions, we'll skip the tests that relating to that. ::
364
return self.branch_format.initialize(repo.bzrdir)
365
except errors.UninitializableFormat:
366
raise tests.TestSkipped('Uninitializable branch format')
368
Raising TestSkipped is a good idea when you want to make it clear that the
369
test was not run, rather than just returning which makes it look as if it
372
Several different cases are distinguished:
375
Generic skip; the only type that was present up to bzr 0.18.
378
The test doesn't apply to the parameters with which it was run.
379
This is typically used when the test is being applied to all
380
implementations of an interface, but some aspects of the interface
381
are optional and not present in particular concrete
382
implementations. (Some tests that should raise this currently
383
either silently return or raise TestSkipped.) Another option is
384
to use more precise parameterization to avoid generating the test
388
**(Not implemented yet)**
389
The test can't be run because of an inherent limitation of the
390
environment, such as not having symlinks or not supporting
394
The test can't be run because a dependency (typically a Python
395
library) is not available in the test environment. These
396
are in general things that the person running the test could fix
397
by installing the library. It's OK if some of these occur when
398
an end user runs the tests or if we're specifically testing in a
399
limited environment, but a full test should never see them.
402
The test exists but is known to fail, for example because the
403
code to fix it hasn't been run yet. Raising this allows
404
you to distinguish these failures from the ones that are not
405
expected to fail. This could be conditionally raised if something
406
is broken on some platforms but not on others.
408
We plan to support three modes for running the test suite to control the
409
interpretation of these results. Strict mode is for use in situations
410
like merges to the mainline and releases where we want to make sure that
411
everything that can be tested has been tested. Lax mode is for use by
412
developers who want to temporarily tolerate some known failures. The
413
default behaviour is obtained by ``bzr selftest`` with no options, and
414
also (if possible) by running under another unittest harness.
416
======================= ======= ======= ========
417
result strict default lax
418
======================= ======= ======= ========
419
TestSkipped pass pass pass
420
TestNotApplicable pass pass pass
421
TestPlatformLimit pass pass pass
422
TestDependencyMissing fail pass pass
423
KnownFailure fail pass pass
424
======================= ======= ======= ========
427
Test feature dependencies
428
-------------------------
430
Rather than manually checking the environment in each test, a test class
431
can declare its dependence on some test features. The feature objects are
432
checked only once for each run of the whole test suite.
434
For historical reasons, as of May 2007 many cases that should depend on
435
features currently raise TestSkipped.)
439
class TestStrace(TestCaseWithTransport):
441
_test_needs_features = [StraceFeature]
443
This means all tests in this class need the feature. The feature itself
444
should provide a ``_probe`` method which is called once to determine if
447
These should generally be equivalent to either TestDependencyMissing or
448
sometimes TestPlatformLimit.
454
Known failures are when a test exists but we know it currently doesn't
455
work, allowing the test suite to still pass. These should be used with
456
care, we don't want a proliferation of quietly broken tests. It might be
457
appropriate to use them if you've committed a test for a bug but not the
458
fix for it, or if something works on Unix but not on Windows.
461
Testing exceptions and errors
462
-----------------------------
464
It's important to test handling of errors and exceptions. Because this
465
code is often not hit in ad-hoc testing it can often have hidden bugs --
466
it's particularly common to get NameError because the exception code
467
references a variable that has since been renamed.
469
.. TODO: Something about how to provoke errors in the right way?
471
In general we want to test errors at two levels:
473
1. A test in ``test_errors.py`` checking that when the exception object is
474
constructed with known parameters it produces an expected string form.
475
This guards against mistakes in writing the format string, or in the
476
``str`` representations of its parameters. There should be one for
477
each exception class.
479
2. Tests that when an api is called in a particular situation, it raises
480
an error of the expected class. You should typically use
481
``assertRaises``, which in the Bazaar test suite returns the exception
482
object to allow you to examine its parameters.
484
In some cases blackbox tests will also want to check error reporting. But
485
it can be difficult to provoke every error through the commandline
486
interface, so those tests are only done as needed -- eg in response to a
487
particular bug or if the error is reported in an unusual way(?) Blackbox
488
tests should mostly be testing how the command-line interface works, so
489
should only test errors if there is something particular to the cli in how
490
they're displayed or handled.
496
The Python ``warnings`` module is used to indicate a non-fatal code
497
problem. Code that's expected to raise a warning can be tested through
500
The test suite can be run with ``-Werror`` to check no unexpected errors
503
However, warnings should be used with discretion. It's not an appropriate
504
way to give messages to the user, because the warning is normally shown
505
only once per source line that causes the problem. You should also think
506
about whether the warning is serious enought that it should be visible to
507
users who may not be able to fix it.
510
Interface implementation testing and test scenarios
511
---------------------------------------------------
513
There are several cases in Bazaar of multiple implementations of a common
514
conceptual interface. ("Conceptual" because
515
it's not necessary for all the implementations to share a base class,
516
though they often do.) Examples include transports and the working tree,
517
branch and repository classes.
519
In these cases we want to make sure that every implementation correctly
520
fulfils the interface requirements. For example, every Transport should
521
support the ``has()`` and ``get()`` and ``clone()`` methods. We have a
522
sub-suite of tests in ``test_transport_implementations``. (Most
523
per-implementation tests are in submodules of ``bzrlib.tests``, but not
524
the transport tests at the moment.)
526
These tests are repeated for each registered Transport, by generating a
527
new TestCase instance for the cross product of test methods and transport
528
implementations. As each test runs, it has ``transport_class`` and
529
``transport_server`` set to the class it should test. Most tests don't
530
access these directly, but rather use ``self.get_transport`` which returns
531
a transport of the appropriate type.
533
The goal is to run per-implementation only tests that relate to that
534
particular interface. Sometimes we discover a bug elsewhere that happens
535
with only one particular transport. Once it's isolated, we can consider
536
whether a test should be added for that particular implementation,
537
or for all implementations of the interface.
539
The multiplication of tests for different implementations is normally
540
accomplished by overriding the ``test_suite`` function used to load
541
tests from a module. This function typically loads all the tests,
542
then applies a TestProviderAdapter to them, which generates a longer
543
suite containing all the test variations.
549
Some utilities are provided for generating variations of tests. This can
550
be used for per-implementation tests, or other cases where the same test
551
code needs to run several times on different scenarios.
553
The general approach is to define a class that provides test methods,
554
which depend on attributes of the test object being pre-set with the
555
values to which the test should be applied. The test suite should then
556
also provide a list of scenarios in which to run the tests.
558
Typically ``multiply_tests_from_modules`` should be called from the test
559
module's ``test_suite`` function.
562
Essential Domain Classes
563
########################
565
Introducing the Object Model
566
============================
568
The core domain objects within the bazaar model are:
578
Transports are explained below. See http://bazaar-vcs.org/Classes/
579
for an introduction to the other key classes.
584
The ``Transport`` layer handles access to local or remote directories.
585
Each Transport object acts like a logical connection to a particular
586
directory, and it allows various operations on files within it. You can
587
*clone* a transport to get a new Transport connected to a subdirectory or
590
Transports are not used for access to the working tree. At present
591
working trees are always local and they are accessed through the regular
592
Python file io mechanisms.
597
Transports work in URLs. Take note that URLs are by definition only
598
ASCII - the decision of how to encode a Unicode string into a URL must be
599
taken at a higher level, typically in the Store. (Note that Stores also
600
escape filenames which cannot be safely stored on all filesystems, but
601
this is a different level.)
603
The main reason for this is that it's not possible to safely roundtrip a
604
URL into Unicode and then back into the same URL. The URL standard
605
gives a way to represent non-ASCII bytes in ASCII (as %-escapes), but
606
doesn't say how those bytes represent non-ASCII characters. (They're not
607
guaranteed to be UTF-8 -- that is common but doesn't happen everywhere.)
609
For example if the user enters the url ``http://example/%e0`` there's no
610
way to tell whether that character represents "latin small letter a with
611
grave" in iso-8859-1, or "latin small letter r with acute" in iso-8859-2
612
or malformed UTF-8. So we can't convert their URL to Unicode reliably.
614
Equally problematic if we're given a url-like string containing non-ascii
615
characters (such as the accented a) we can't be sure how to convert that
616
to the correct URL, because we don't know what encoding the server expects
617
for those characters. (Although this is not totally reliable we might still
618
accept these and assume they should be put into UTF-8.)
620
A similar edge case is that the url ``http://foo/sweet%2Fsour`` contains
621
one directory component whose name is "sweet/sour". The escaped slash is
622
not a directory separator. If we try to convert URLs to regular Unicode
623
paths this information will be lost.
625
This implies that Transports must natively deal with URLs; for simplicity
626
they *only* deal with URLs and conversion of other strings to URLs is done
627
elsewhere. Information they return, such as from ``list_dir``, is also in
628
the form of URL components.
352
679
the expected deprecation message, and also returns the real result from
353
680
the method, so that tests can keep running.
355
Deprecation warnings will be suppressed for final releases, but not for
356
development versions or release candidates, or when running ``bzr
357
selftest``. This gives developers information about whether their code is
358
using deprecated functions, but avoids confusing users about things they
682
Coding Style Guidelines
683
=======================
688
``hasattr`` should not be used because it swallows exceptions including
689
``KeyboardInterrupt``. Instead, say something like ::
691
if getattr(thing, 'name', None) is None
697
Please write PEP-8__ compliant code.
699
__ http://www.python.org/peps/pep-0008.html
701
One often-missed requirement is that the first line of docstrings
702
should be a self-contained one-sentence summary.
704
We use 4 space indents for blocks, and never use tab characters. (In vim,
707
Lines should be no more than 79 characters if at all possible.
708
Lines that continue a long statement may be indented in either of
711
within the parenthesis or other character that opens the block, e.g.::
717
or indented by four spaces::
723
The first is considered clearer by some people; however it can be a bit
724
harder to maintain (e.g. when the method name changes), and it does not
725
work well if the relevant parenthesis is already far to the right. Avoid
728
self.legbone.kneebone.shinbone.toebone.shake_it(one,
734
self.legbone.kneebone.shinbone.toebone.shake_it(one,
740
self.legbone.kneebone.shinbone.toebone.shake_it(
743
For long lists, we like to add a trailing comma and put the closing
744
character on the following line. This makes it easier to add new items in
747
from bzrlib.goo import (
753
There should be spaces between function paramaters, but not between the
754
keyword name and the value::
756
call(1, 3, cheese=quark)
760
;(defface my-invalid-face
761
; '((t (:background "Red" :underline t)))
762
; "Face used to highlight invalid constructs or other uglyties"
765
(defun my-python-mode-hook ()
766
;; setup preferred indentation style.
767
(setq fill-column 79)
768
(setq indent-tabs-mode nil) ; no tabs, never, I will not repeat
769
; (font-lock-add-keywords 'python-mode
770
; '(("^\\s *\t" . 'my-invalid-face) ; Leading tabs
771
; ("[ \t]+$" . 'my-invalid-face) ; Trailing spaces
772
; ("^[ \t]+$" . 'my-invalid-face)); Spaces only
776
(add-hook 'python-mode-hook 'my-python-mode-hook)
778
The lines beginning with ';' are comments. They can be activated
779
if one want to have a strong notice of some tab/space usage
786
* Imports should be done at the top-level of the file, unless there is
787
a strong reason to have them lazily loaded when a particular
788
function runs. Import statements have a cost, so try to make sure
789
they don't run inside hot functions.
791
* Module names should always be given fully-qualified,
792
i.e. ``bzrlib.hashcache`` not just ``hashcache``.
798
Functions, methods or members that are "private" to bzrlib are given
799
a leading underscore prefix. Names without a leading underscore are
800
public not just across modules but to programmers using bzrlib as an
801
API. As a consequence, a leading underscore is appropriate for names
802
exposed across modules but that are not to be exposed to bzrlib API
805
We prefer class names to be concatenated capital words (``TestCase``)
806
and variables, methods and functions to be lowercase words joined by
807
underscores (``revision_id``, ``get_revision``).
809
For the purposes of naming some names are treated as single compound
810
words: "filename", "revno".
812
Consider naming classes as nouns and functions/methods as verbs.
814
Try to avoid using abbreviations in names, because there can be
815
inconsistency if other people use the full name.
821
``revision_id`` not ``rev_id`` or ``revid``
823
Functions that transform one thing to another should be named ``x_to_y``
824
(not ``x2y`` as occurs in some old code.)
830
Python destructors (``__del__``) work differently to those of other
831
languages. In particular, bear in mind that destructors may be called
832
immediately when the object apparently becomes unreferenced, or at some
833
later time, or possibly never at all. Therefore we have restrictions on
834
what can be done inside them.
836
0. Never use a __del__ method without asking Martin/Robert first.
838
1. Never rely on a ``__del__`` method running. If there is code that
839
must run, do it from a ``finally`` block instead.
841
2. Never ``import`` from inside a ``__del__`` method, or you may crash the
844
3. In some places we raise a warning from the destructor if the object
845
has not been cleaned up or closed. This is considered OK: the warning
846
may not catch every case but it's still useful sometimes.
852
In some places we have variables which point to callables that construct
853
new instances. That is to say, they can be used a lot like class objects,
854
but they shouldn't be *named* like classes:
856
> I think that things named FooBar should create instances of FooBar when
857
> called. Its plain confusing for them to do otherwise. When we have
858
> something that is going to be used as a class - that is, checked for via
859
> isinstance or other such idioms, them I would call it foo_class, so that
860
> it is clear that a callable is not sufficient. If it is only used as a
861
> factory, then yes, foo_factory is what I would use.
867
Several places in Bazaar use (or will use) a registry, which is a
868
mapping from names to objects or classes. The registry allows for
869
loading in registered code only when it's needed, and keeping
870
associated information such as a help string or description.
876
To make startup time faster, we use the ``bzrlib.lazy_import`` module to
877
delay importing modules until they are actually used. ``lazy_import`` uses
878
the same syntax as regular python imports. So to import a few modules in a
881
from bzrlib.lazy_import import lazy_import
882
lazy_import(globals(), """
891
revision as _mod_revision,
893
import bzrlib.transport
897
At this point, all of these exist as a ``ImportReplacer`` object, ready to
898
be imported once a member is accessed. Also, when importing a module into
899
the local namespace, which is likely to clash with variable names, it is
900
recommended to prefix it as ``_mod_<module>``. This makes it clearer that
901
the variable is a module, and these object should be hidden anyway, since
902
they shouldn't be imported into other namespaces.
905
Modules versus Members
906
~~~~~~~~~~~~~~~~~~~~~~
908
While it is possible for ``lazy_import()`` to import members of a module
909
when using the ``from module import member`` syntax, it is recommended to
910
only use that syntax to load sub modules ``from module import submodule``.
911
This is because variables and classes can frequently be used without
912
needing a sub-member for example::
914
lazy_import(globals(), """
915
from module import MyClass
919
return isinstance(x, MyClass)
921
This will incorrectly fail, because ``MyClass`` is a ``ImportReplacer``
922
object, rather than the real class.
925
Passing to Other Variables
926
~~~~~~~~~~~~~~~~~~~~~~~~~~
928
It also is incorrect to assign ``ImportReplacer`` objects to other variables.
929
Because the replacer only knows about the original name, it is unable to
930
replace other variables. The ``ImportReplacer`` class will raise an
931
``IllegalUseOfScopeReplacer`` exception if it can figure out that this
932
happened. But it requires accessing a member more than once from the new
933
variable, so some bugs are not detected right away.
939
The null revision is the ancestor of all revisions. Its revno is 0, its
940
revision-id is ``null:``, and its tree is the empty tree. When referring
941
to the null revision, please use ``bzrlib.revision.NULL_REVISION``. Old
942
code sometimes uses ``None`` for the null revision, but this practice is
949
Processing Command Lines
950
------------------------
952
bzrlib has a standard framework for parsing command lines and calling
953
processing routines associated with various commands. See builtins.py
954
for numerous examples.
957
Standard Parameter Types
958
------------------------
960
There are some common requirements in the library: some parameters need to be
961
unicode safe, some need byte strings, and so on. At the moment we have
962
only codified one specific pattern: Parameters that need to be unicode
963
should be checked via ``bzrlib.osutils.safe_unicode``. This will coerce the
964
input into unicode in a consistent fashion, allowing trivial strings to be
965
used for programmer convenience, but not performing unpredictably in the
966
presence of different locales.
972
(The strategy described here is what we want to get to, but it's not
973
consistently followed in the code at the moment.)
975
bzrlib is intended to be a generically reusable library. It shouldn't
976
write messages to stdout or stderr, because some programs that use it
977
might want to display that information through a GUI or some other
980
We can distinguish two types of output from the library:
982
1. Structured data representing the progress or result of an
983
operation. For example, for a commit command this will be a list
984
of the modified files and the finally committed revision number
987
These should be exposed either through the return code or by calls
988
to a callback parameter.
990
A special case of this is progress indicators for long-lived
991
operations, where the caller should pass a ProgressBar object.
993
2. Unstructured log/debug messages, mostly for the benefit of the
994
developers or users trying to debug problems. This should always
995
be sent through ``bzrlib.trace`` and Python ``logging``, so that
996
it can be redirected by the client.
998
The distinction between the two is a bit subjective, but in general if
999
there is any chance that a library would want to see something as
1000
structured data, we should make it so.
1002
The policy about how output is presented in the text-mode client
1003
should be only in the command-line tool.
1010
Bazaar has online help for various topics through ``bzr help COMMAND`` or
1011
equivalently ``bzr command -h``. We also have help on command options,
1012
and on other help topics. (See ``help_topics.py``.)
1014
As for python docstrings, the first paragraph should be a single-sentence
1015
synopsis of the command.
1017
The help for options should be one or more proper sentences, starting with
1018
a capital letter and finishing with a full stop (period).
1020
All help messages and documentation should have two spaces between
1027
In general tests should be placed in a file named test_FOO.py where
1028
FOO is the logical thing under test. That file should be placed in the
1029
tests subdirectory under the package being tested.
1031
For example, tests for merge3 in bzrlib belong in bzrlib/tests/test_merge3.py.
1032
See bzrlib/tests/test_sampler.py for a template test script.
1034
Tests can be written for the UI or for individual areas of the library.
1035
Choose whichever is appropriate: if adding a new command, or a new command
1036
option, then you should be writing a UI test. If you are both adding UI
1037
functionality and library functionality, you will want to write tests for
1038
both the UI and the core behaviours. We call UI tests 'blackbox' tests
1039
and they are found in ``bzrlib/tests/blackbox/*.py``.
1041
When writing blackbox tests please honour the following conventions:
1043
1. Place the tests for the command 'name' in
1044
bzrlib/tests/blackbox/test_name.py. This makes it easy for developers
1045
to locate the test script for a faulty command.
1047
2. Use the 'self.run_bzr("name")' utility function to invoke the command
1048
rather than running bzr in a subprocess or invoking the
1049
cmd_object.run() method directly. This is a lot faster than
1050
subprocesses and generates the same logging output as running it in a
1051
subprocess (which invoking the method directly does not).
1053
3. Only test the one command in a single test script. Use the bzrlib
1054
library when setting up tests and when evaluating the side-effects of
1055
the command. We do this so that the library api has continual pressure
1056
on it to be as functional as the command line in a simple manner, and
1057
to isolate knock-on effects throughout the blackbox test suite when a
1058
command changes its name or signature. Ideally only the tests for a
1059
given command are affected when a given command is changed.
1061
4. If you have a test which does actually require running bzr in a
1062
subprocess you can use ``run_bzr_subprocess``. By default the spawned
1063
process will not load plugins unless ``--allow-plugins`` is supplied.
1069
We have a rich collection of tools to support writing tests. Please use
1070
them in preference to ad-hoc solutions as they provide portability and
1071
performance benefits.
1076
The ``TreeBuilder`` interface allows the construction of arbitrary trees
1077
with a declarative interface. A sample session might look like::
1079
tree = self.make_branch_and_tree('path')
1080
builder = TreeBuilder()
1081
builder.start_tree(tree)
1082
builder.build(['foo', "bar/", "bar/file"])
1083
tree.commit('commit the tree')
1084
builder.finish_tree()
1086
Please see bzrlib.treebuilder for more details.
1091
The ``BranchBuilder`` interface allows the creation of test branches in a
1092
quick and easy manner. A sample session::
1094
builder = BranchBuilder(self.get_transport().clone('relpath'))
1095
builder.build_commit()
1096
builder.build_commit()
1097
builder.build_commit()
1098
branch = builder.get_branch()
1100
Please see bzrlib.branchbuilder for more details.
1105
We make selective use of doctests__. In general they should provide
1106
*examples* within the API documentation which can incidentally be tested. We
1107
don't try to test every important case using doctests -- regular Python
1108
tests are generally a better solution.
1110
Most of these are in ``bzrlib/doc/api``. More additions are welcome.
1112
__ http://docs.python.org/lib/module-doctest.html
1117
Currently, bzr selftest is used to invoke tests.
1118
You can provide a pattern argument to run a subset. For example,
1119
to run just the blackbox tests, run::
1121
./bzr selftest -v blackbox
1123
To skip a particular test (or set of tests), use the --exclude option
1124
(shorthand -x) like so::
1126
./bzr selftest -v -x blackbox
1128
To list tests without running them, use the --list-only option like so::
1130
./bzr selftest --list-only
1132
This option can be combined with other selftest options (like -x) and
1133
filter patterns to understand their effect.
1136
Handling Errors and Exceptions
1137
==============================
1139
Commands should return non-zero when they encounter circumstances that
1140
the user should really pay attention to - which includes trivial shell
1143
Recommended values are:
1146
1. Conflicts in merge-like operations, or changes are present in
1147
diff-like operations.
1148
2. Unrepresentable diff changes (i.e. binary files that we cannot show
1150
3. An error or exception has occurred.
1151
4. An internal error occurred (one that shows a traceback.)
1153
Errors are handled through Python exceptions. Exceptions should be defined
1154
inside bzrlib.errors, so that we can see the whole tree at a glance.
1156
We broadly classify errors as either being either internal or not,
1157
depending on whether ``internal_error`` is set or not. If we think it's our
1158
fault, we show a backtrace, an invitation to report the bug, and possibly
1159
other details. This is the default for errors that aren't specifically
1160
recognized as being caused by a user error. Otherwise we show a briefer
1161
message, unless -Derror was given.
1163
Many errors originate as "environmental errors" which are raised by Python
1164
or builtin libraries -- for example IOError. These are treated as being
1165
our fault, unless they're caught in a particular tight scope where we know
1166
that they indicate a user errors. For example if the repository format
1167
is not found, the user probably gave the wrong path or URL. But if one of
1168
the files inside the repository is not found, then it's our fault --
1169
either there's a bug in bzr, or something complicated has gone wrong in
1170
the environment that means one internal file was deleted.
1172
Many errors are defined in ``bzrlib/errors.py`` but it's OK for new errors
1173
to be added near the place where they are used.
1175
Exceptions are formatted for the user by conversion to a string
1176
(eventually calling their ``__str__`` method.) As a convenience the
1177
``._fmt`` member can be used as a template which will be mapped to the
1178
error's instance dict.
1180
New exception classes should be defined when callers might want to catch
1181
that exception specifically, or when it needs a substantially different
1184
Exception strings should start with a capital letter and should not have a
1185
final fullstop. If long, they may contain newlines to break the text.
1191
Do not use the Python ``assert`` statement, either in tests or elsewhere.
1192
A source test checks that it is not used. It is ok to explicitly raise
1197
* It makes the behaviour vary depending on whether bzr is run with -O
1198
or not, therefore giving a chance for bugs that occur in one case or
1199
the other, several of which have already occurred: assertions with
1200
side effects, code which can't continue unless the assertion passes,
1201
cases where we should give the user a proper message rather than an
1203
* It's not that much shorter than an explicit if/raise.
1204
* It tends to lead to fuzzy thinking about whether the check is
1205
actually needed or not, and whether it's an internal error or not
1206
* It tends to cause look-before-you-leap patterns.
1207
* It's unsafe if the check is needed to protect the integrity of the
1209
* It tends to give poor messages since the developer can get by with
1210
no explanatory text at all.
1211
* We can't rely on people always running with -O in normal use, so we
1212
can't use it for tests that are actually expensive.
1213
* Expensive checks that help developers are better turned on from the
1214
test suite or a -D flag.
1215
* If used instead of ``self.assert*()`` in tests it makes them falsely pass with -O.
1221
When you change bzrlib, please update the relevant documentation for the
1222
change you made: Changes to commands should update their help, and
1223
possibly end user tutorials; changes to the core library should be
1224
reflected in API documentation.
1229
If you make a user-visible change, please add a note to the NEWS file.
1230
The description should be written to make sense to someone who's just
1231
a user of bzr, not a developer: new functions or classes shouldn't be
1232
mentioned, but new commands, changes in behaviour or fixed nontrivial
1233
bugs should be listed. See the existing entries for an idea of what
1236
Within each release, entries in the news file should have the most
1237
user-visible changes first. So the order should be approximately:
1239
* changes to existing behaviour - the highest priority because the
1240
user's existing knowledge is incorrect
1241
* new features - should be brought to their attention
1242
* bug fixes - may be of interest if the bug was affecting them, and
1243
should include the bug number if any
1244
* major documentation changes
1245
* changes to internal interfaces
1247
People who made significant contributions to each change are listed in
1248
parenthesis. This can include reporting bugs (particularly with good
1249
details or reproduction recipes), submitting patches, etc.
1254
The docstring of a command is used by ``bzr help`` to generate help output
1255
for the command. The list 'takes_options' attribute on a command is used by
1256
``bzr help`` to document the options for the command - the command
1257
docstring does not need to document them. Finally, the '_see_also'
1258
attribute on a command can be used to reference other related help topics.
1263
Functions, methods, classes and modules should have docstrings
1264
describing how they are used.
1266
The first line of the docstring should be a self-contained sentence.
1268
For the special case of Command classes, this acts as the user-visible
1269
documentation shown by the help command.
1271
The docstrings should be formatted as reStructuredText_ (like this
1272
document), suitable for processing using the epydoc_ tool into HTML
1275
.. _reStructuredText: http://docutils.sourceforge.net/rst.html
1276
.. _epydoc: http://epydoc.sourceforge.net/
362
1279
General Guidelines
621
1548
how to set it up and configure it.
1554
Setting Up Your Workspace for Reviews
1555
-------------------------------------
1557
TODO: Incorporate John Arbash Meinel's detailed email to Ian C on the
1558
numerous ways of setting up integration branches.
1561
The Review Checklist
1562
--------------------
1564
See `A Closer Look at the Merge & Review Process`_
1565
for information on the gates used to decide whether code can be merged
1566
or not and details on how review results are recorded and communicated.
1569
The Importance of Timely Reviews
1570
--------------------------------
1572
Good reviews do take time. They also regularly require a solid
1573
understanding of the overall code base. In practice, this means a small
1574
number of people often have a large review burden - with knowledge comes
1575
responsibility. No one like their merge requests sitting in a queue going
1576
nowhere, so reviewing sooner rather than later is strongly encouraged.
1585
Of the many workflows supported by Bazaar, the one adopted for Bazaar
1586
development itself is known as "Decentralized with automatic gatekeeper".
1587
To repeat the explanation of this given on
1588
http://bazaar-vcs.org/Workflows:
1591
In this workflow, each developer has their own branch or
1592
branches, plus read-only access to the mainline. A software gatekeeper
1593
(e.g. PQM) has commit rights to the main branch. When a developer wants
1594
their work merged, they request the gatekeeper to merge it. The gatekeeper
1595
does a merge, a compile, and runs the test suite. If the code passes, it
1596
is merged into the mainline.
1598
In a nutshell, here's the overall submission process:
1600
#. get your work ready (including review except for trivial changes)
1601
#. push to a public location
1602
#. ask PQM to merge from that location
1605
At present, PQM always takes the changes to merge from a branch
1606
at a URL that can be read by it. For Bazaar, that means a public,
1607
typically http, URL.
1609
As a result, the following things are needed to use PQM for submissions:
1611
#. A publicly available web server
1612
#. Your OpenPGP key registered with PQM (contact RobertCollins for this)
1613
#. The PQM plugin installed and configured (not strictly required but
1614
highly recommended).
1617
Selecting a Public Branch Location
1618
----------------------------------
1620
If you don't have your own web server running, branches can always be
1621
pushed to Launchpad. Here's the process for doing that:
1623
Depending on your location throughout the world and the size of your
1624
repository though, it is often quicker to use an alternative public
1625
location to Launchpad, particularly if you can set up your own repo and
1626
push into that. By using an existing repo, push only needs to send the
1627
changes, instead of the complete repository every time. Note that it is
1628
easy to register branches in other locations with Launchpad so no benefits
1629
are lost by going this way.
1632
For Canonical staff, http://people.ubuntu.com/~<user>/ is one
1633
suggestion for public http branches. Contact your manager for information
1634
on accessing this system if required.
1636
It should also be noted that best practice in this area is subject to
1637
change as things evolve. For example, once the Bazaar smart server on
1638
Launchpad supports server-side branching, the performance situation will
1639
be very different to what it is now (Jun 2007).
1642
Configuring the PQM Plug-In
1643
---------------------------
1645
While not strictly required, the PQM plugin automates a few things and
1646
reduces the chance of error. Before looking at the plugin, it helps to
1647
understand a little more how PQM operates. Basically, PQM requires an
1648
email indicating what you want it to do. The email typically looks like
1651
star-merge source-branch target-branch
1655
star-merge http://bzr.arbash-meinel.com/branches/bzr/jam-integration http://bazaar-vcs.org/bzr/bzr.dev
1657
Note that the command needs to be on one line. The subject of the email
1658
will be used for the commit message. The email also needs to be ``gpg``
1659
signed with a key that PQM accepts.
1661
The advantages of using the PQM plugin are:
1663
#. You can use the config policies to make it easy to set up public
1664
branches, so you don't have to ever type the full paths you want to merge
1667
#. It checks to make sure the public branch last revision matches the
1668
local last revision so you are submitting what you think you are.
1670
#. It uses the same public_branch and smtp sending settings as bzr-email,
1671
so if you have one set up, you have the other mostly set up.
1673
#. Thunderbird refuses to not wrap lines, and request lines are usually
1674
pretty long (you have 2 long URLs in there).
1676
Here are sample configuration settings for the PQM plugin. Here are the
1677
lines in bazaar.conf::
1680
email = Joe Smith <joe.smith@internode.on.net>
1681
smtp_server=mail.internode.on.net:25
1683
And here are the lines in ``locations.conf`` (or ``branch.conf`` for
1684
dirstate-tags branches)::
1686
[/home/joe/bzr/my-integration]
1687
push_location = sftp://joe-smith@bazaar.launchpad.net/%7Ejoe-smith/bzr/my-integration/
1688
push_location:policy = norecurse
1689
public_branch = http://bazaar.launchpad.net/~joe-smith/bzr/my-integration/
1690
public_branch:policy = appendpath
1691
pqm_email = Bazaar PQM <pqm@bazaar-vcs.org>
1692
pqm_branch = http://bazaar-vcs.org/bzr/bzr.dev
1694
Note that the push settings will be added by the first ``push`` on
1695
a branch. Indeed the preferred way to generate the lines above is to use
1696
``push`` with an argument, then copy-and-paste the other lines into
1703
Here is one possible recipe once the above environment is set up:
1705
#. pull bzr.dev => my-integration
1706
#. merge patch => my-integration
1707
#. fix up any final merge conflicts (NEWS being the big killer here).
1713
The ``push`` step is not required if ``my-integration`` is a checkout of
1716
Because of defaults, you can type a single message into commit and
1717
pqm-commit will reuse that.
1720
Tracking Change Acceptance
1721
--------------------------
1723
The web interface to PQM is https://pqm.bazaar-vcs.org/. After submitting
1724
a change, you can visit this URL to confirm it was received and placed in
1727
When PQM completes processing a change, an email is sent to you with the
1731
Reviewing Blueprints
1732
====================
1734
Blueprint Tracking Using Launchpad
1735
----------------------------------
1737
New features typically require a fair amount of discussion, design and
1738
debate. For Bazaar, that information is often captured in a so-called
1739
"blueprint" on our Wiki. Overall tracking of blueprints and their status
1740
is done using Launchpad's relevant tracker,
1741
https://blueprints.launchpad.net/bzr/. Once a blueprint for ready for
1742
review, please announce it on the mailing list.
1744
Alternatively, send an email begining with [RFC] with the proposal to the
1745
list. In some cases, you may wish to attach proposed code or a proposed
1746
developer document if that best communicates the idea. Debate can then
1747
proceed using the normal merge review processes.
1750
Recording Blueprint Review Feedback
1751
-----------------------------------
1753
Unlike its Bug Tracker, Launchpad's Blueprint Tracker doesn't currently
1754
(Jun 2007) support a chronological list of comment responses. Review
1755
feedback can either be recorded on the Wiki hosting the blueprints or by
1756
using Launchpad's whiteboard feature.
625
1759
Planning Releases
626
1760
=================
1765
As the two senior developers, Martin Pool and Robert Collins coordinate
1766
the overall Bazaar product development roadmap. Core developers provide
1767
input and review into this, particularly during sprints. It's totally
1768
expected that community members ought to be working on things that
1769
interest them the most. The roadmap is valuable though because it provides
1770
context for understanding where the product is going as a whole and why.
1773
Using Releases and Milestones in Launchpad
1774
------------------------------------------
1776
TODO ... (Exact policies still under discussion)
added
removed
doc/developers/HACKING.txt
