73
82
Bazaar Development in a Nutshell
74
83
================================
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
85
Looking for a 10 minute introduction to submitting a change?
86
See http://bazaar-vcs.org/BzrGivingBack.
88
TODO: Merge that Wiki page into this document.
184
91
Understanding the Development Process
278
187
Holds documentation on a whole range of things on Bazaar from the
279
188
origination of ideas within the project to information on Bazaar
280
189
features and use cases. Within this directory there is a subdirectory
281
for each translation into a human language. All the documentation
190
for each translation into a human language. All the documentation
282
191
is in the ReStructuredText markup language.
285
Documentation specifically targeted at Bazaar and plugin developers.
194
Documentation specifically targetted at Bazaar and plugin developers.
286
195
(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>`_.
199
Automatically-generated API reference information is available at
200
<http://starship.python.net/crew/mwh/bzrlibapi/>.
202
See also the `Bazaar Architectural Overview <../../developers/overview.html>`_.
205
The Code Review Process
206
#######################
208
All code changes coming in to Bazaar are reviewed by someone else.
209
Normally changes by core contributors are reviewed by one other core
210
developer, and changes from other people are reviewed by two core
211
developers. Use intelligent discretion if the patch is trivial.
213
Good reviews do take time. They also regularly require a solid
214
understanding of the overall code base. In practice, this means a small
215
number of people often have a large review burden - with knowledge comes
216
responsibility. No one like their merge requests sitting in a queue going
217
nowhere, so reviewing sooner rather than later is strongly encouraged.
226
Please put a "cover letter" on your merge request explaining:
228
* the reason **why** you're making this change
230
* **how** this change achieves this purpose
232
* anything else you may have fixed in passing
234
* anything significant that you thought of doing, such as a more
235
extensive fix or a different approach, but didn't or couldn't do now
237
A good cover letter makes reviewers' lives easier because they can decide
238
from the letter whether they agree with the purpose and approach, and then
239
assess whether the patch actually does what the cover letter says.
240
Explaining any "drive-by fixes" or roads not taken may also avoid queries
241
from the reviewer. All in all this should give faster and better reviews.
242
Sometimes writing the cover letter helps the submitter realize something
243
else they need to do. The size of the cover letter should be proportional
244
to the size and complexity of the patch.
247
Reviewing proposed changes
248
==========================
250
Anyone is welcome to review code, and reply to the thread with their
253
The simplest way to review a proposed change is to just read the patch on
254
the list or in Bundle Buggy. For more complex changes it may be useful
255
to make a new working tree or branch from trunk, and merge the proposed
256
change into it, so you can experiment with the code or look at a wider
259
There are three main requirements for code to get in:
261
* Doesn't reduce test coverage: if it adds new methods or commands,
262
there should be tests for them. There is a good test framework
263
and plenty of examples to crib from, but if you are having trouble
264
working out how to test something feel free to post a draft patch
267
* Doesn't reduce design clarity, such as by entangling objects
268
we're trying to separate. This is mostly something the more
269
experienced reviewers need to help check.
271
* Improves bugs, features, speed, or code simplicity.
273
Code that goes in should not degrade any of these aspects. Patches are
274
welcome that only cleanup the code without changing the external
275
behaviour. The core developers take care to keep the code quality high
276
and understandable while recognising that perfect is sometimes the enemy
279
It is easy for reviews to make people notice other things which should be
280
fixed but those things should not hold up the original fix being accepted.
281
New things can easily be recorded in the Bug Tracker instead.
283
It's normally much easier to review several smaller patches than one large
284
one. You might want to use ``bzr-loom`` to maintain threads of related
285
work, or submit a preparatory patch that will make your "real" change
289
Checklist for reviewers
290
=======================
292
* Do you understand what the code's doing and why?
294
* Will it perform reasonably for large inputs, both in memory size and
295
run time? Are there some scenarios where performance should be
298
* Is it tested, and are the tests at the right level? Are there both
299
blackbox (command-line level) and API-oriented tests?
301
* If this change will be visible to end users or API users, is it
302
appropriately documented in NEWS?
304
* Does it meet the coding standards below?
306
* If it changes the user-visible behaviour, does it update the help
307
strings and user documentation?
309
* If it adds a new major concept or standard practice, does it update the
310
developer documentation?
312
* (your ideas here...)
318
From May 2009 on, we prefer people to propose code reviews through
321
* <https://launchpad.net/+tour/code-review>
323
* <https://help.launchpad.net/Code/Review>
325
Anyone can propose or comment on a merge propsal just by creating a
328
There are two ways to create a new merge proposal: through the web
329
interface or by email.
332
Proposing a merge through the web
333
---------------------------------
335
To create the propsal through the web: push your branch to Launchpad, eg::
337
bzr push lp:~mbp/bzr/doc
339
then go to the branch's web page, which in this case would be
340
<https://code.launchpad.net/~mbp/bzr/doc>. You can automate that by just
345
You can then click "Propose for merging into another branch", and enter a
346
cover letter into the web form. Typically you'll want to merge into
347
``~bzr/bzr/trunk`` which will be the default; you might also want to
348
nominate merging into a release branch for a bug fix. There is the option
349
to specify a specific reviewer or type of review, and you shouldn't
350
normally change those.
352
Submitting the form takes you to the new page about the merge proposal
353
containing the diff of the changes, comments by interested people, and
354
controls to comment or vote on the change.
356
Proposing a merge by mail
357
-------------------------
359
To propose a merge by mail, send a bundle to ``merge@code.launchpad.net``.
361
You can generate a merge request like this::
363
bzr send -o bug-1234.diff
365
``bzr send`` can also send mail directly if you prefer; see the help.
370
From <https://code.launchpad.net/bzr/+activereviews> you can see all
371
currently active reviews, and choose one to comment on. This page also
372
shows proposals that are now approved and should be merged by someone with
376
Reviews through Bundle Buggy
377
============================
379
The Bundle Buggy tool used up to May 2009 is still available as a review
382
Sending patches for review
383
--------------------------
385
If you'd like to propose a change, please post to the
386
bazaar@lists.canonical.com list with a bundle, patch, or link to a
387
branch. Put ``[PATCH]`` or ``[MERGE]`` in the subject so Bundle Buggy
388
can pick it out, and explain the change in the email message text.
389
Remember to update the NEWS file as part of your change if it makes any
390
changes visible to users or plugin developers. Please include a diff
391
against mainline if you're giving a link to a branch.
393
You can generate a merge request like this::
395
bzr send -o bug-1234.patch
397
A ``.patch`` extension is recommended instead of .bundle as many mail clients
398
will send the latter as a binary file.
400
``bzr send`` can also send mail directly if you prefer; see the help.
402
Please do **NOT** put [PATCH] or [MERGE] in the subject line if you don't
403
want it to be merged. If you want comments from developers rather than
404
to be merged, you can put ``[RFC]`` in the subject line.
406
If this change addresses a bug, please put the bug number in the subject
407
line too, in the form ``[#1]`` so that Bundle Buggy can recognize it.
409
If the change is intended for a particular release mark that in the
410
subject too, e.g. ``[1.6]``.
411
Anyone can "vote" on the mailing list by expressing an opinion. Core
412
developers can also vote using Bundle Buggy. Here are the voting codes and
415
:approve: Reviewer wants this submission merged.
416
:tweak: Reviewer wants this submission merged with small changes. (No
418
:abstain: Reviewer does not intend to vote on this patch.
419
:resubmit: Please make changes and resubmit for review.
420
:reject: Reviewer doesn't want this kind of change merged.
421
:comment: Not really a vote. Reviewer just wants to comment, for now.
423
If a change gets two approvals from core reviewers, and no rejections,
424
then it's OK to come in. Any of the core developers can bring it into the
425
bzr.dev trunk and backport it to maintenance branches if required. The
426
Release Manager will merge the change into the branch for a pending
427
release, if any. As a guideline, core developers usually merge their own
428
changes and volunteer to merge other contributions if they were the second
429
reviewer to agree to a change.
431
To track the progress of proposed changes, use Bundle Buggy. See
432
http://bundlebuggy.aaronbentley.com/help for a link to all the
433
outstanding merge requests together with an explanation of the columns.
434
Bundle Buggy will also mail you a link to track just your change.
436
Coding Style Guidelines
437
#######################
442
``hasattr`` should not be used because it swallows exceptions including
443
``KeyboardInterrupt``. Instead, say something like ::
445
if getattr(thing, 'name', None) is None
451
Please write PEP-8__ compliant code.
453
__ http://www.python.org/peps/pep-0008.html
455
One often-missed requirement is that the first line of docstrings
456
should be a self-contained one-sentence summary.
458
We use 4 space indents for blocks, and never use tab characters. (In vim,
461
Trailing white space should be avoided, but is allowed.
462
You should however not make lots of unrelated white space changes.
464
Unix style newlines (LF) are used.
466
Each file must have a newline at the end of it.
468
Lines should be no more than 79 characters if at all possible.
469
Lines that continue a long statement may be indented in either of
472
within the parenthesis or other character that opens the block, e.g.::
478
or indented by four spaces::
484
The first is considered clearer by some people; however it can be a bit
485
harder to maintain (e.g. when the method name changes), and it does not
486
work well if the relevant parenthesis is already far to the right. Avoid
489
self.legbone.kneebone.shinbone.toebone.shake_it(one,
495
self.legbone.kneebone.shinbone.toebone.shake_it(one,
501
self.legbone.kneebone.shinbone.toebone.shake_it(
504
For long lists, we like to add a trailing comma and put the closing
505
character on the following line. This makes it easier to add new items in
508
from bzrlib.goo import (
514
There should be spaces between function paramaters, but not between the
515
keyword name and the value::
517
call(1, 3, cheese=quark)
521
;(defface my-invalid-face
522
; '((t (:background "Red" :underline t)))
523
; "Face used to highlight invalid constructs or other uglyties"
526
(defun my-python-mode-hook ()
527
;; setup preferred indentation style.
528
(setq fill-column 79)
529
(setq indent-tabs-mode nil) ; no tabs, never, I will not repeat
530
; (font-lock-add-keywords 'python-mode
531
; '(("^\\s *\t" . 'my-invalid-face) ; Leading tabs
532
; ("[ \t]+$" . 'my-invalid-face) ; Trailing spaces
533
; ("^[ \t]+$" . 'my-invalid-face)); Spaces only
537
(add-hook 'python-mode-hook 'my-python-mode-hook)
539
The lines beginning with ';' are comments. They can be activated
540
if one want to have a strong notice of some tab/space usage
547
* Imports should be done at the top-level of the file, unless there is
548
a strong reason to have them lazily loaded when a particular
549
function runs. Import statements have a cost, so try to make sure
550
they don't run inside hot functions.
552
* Module names should always be given fully-qualified,
553
i.e. ``bzrlib.hashcache`` not just ``hashcache``.
559
Functions, methods or members that are "private" to bzrlib are given
560
a leading underscore prefix. Names without a leading underscore are
561
public not just across modules but to programmers using bzrlib as an
562
API. As a consequence, a leading underscore is appropriate for names
563
exposed across modules but that are not to be exposed to bzrlib API
566
We prefer class names to be concatenated capital words (``TestCase``)
567
and variables, methods and functions to be lowercase words joined by
568
underscores (``revision_id``, ``get_revision``).
570
For the purposes of naming some names are treated as single compound
571
words: "filename", "revno".
573
Consider naming classes as nouns and functions/methods as verbs.
575
Try to avoid using abbreviations in names, because there can be
576
inconsistency if other people use the full name.
582
``revision_id`` not ``rev_id`` or ``revid``
584
Functions that transform one thing to another should be named ``x_to_y``
585
(not ``x2y`` as occurs in some old code.)
591
Python destructors (``__del__``) work differently to those of other
592
languages. In particular, bear in mind that destructors may be called
593
immediately when the object apparently becomes unreferenced, or at some
594
later time, or possibly never at all. Therefore we have restrictions on
595
what can be done inside them.
597
0. If you think you need to use a ``__del__`` method ask another
598
developer for alternatives. If you do need to use one, explain
601
1. Never rely on a ``__del__`` method running. If there is code that
602
must run, do it from a ``finally`` block instead.
604
2. Never ``import`` from inside a ``__del__`` method, or you may crash the
607
3. In some places we raise a warning from the destructor if the object
608
has not been cleaned up or closed. This is considered OK: the warning
609
may not catch every case but it's still useful sometimes.
615
In some places we have variables which point to callables that construct
616
new instances. That is to say, they can be used a lot like class objects,
617
but they shouldn't be *named* like classes:
619
> I think that things named FooBar should create instances of FooBar when
620
> called. Its plain confusing for them to do otherwise. When we have
621
> something that is going to be used as a class - that is, checked for via
622
> isinstance or other such idioms, them I would call it foo_class, so that
623
> it is clear that a callable is not sufficient. If it is only used as a
624
> factory, then yes, foo_factory is what I would use.
630
Several places in Bazaar use (or will use) a registry, which is a
631
mapping from names to objects or classes. The registry allows for
632
loading in registered code only when it's needed, and keeping
633
associated information such as a help string or description.
636
InterObject and multiple dispatch
637
=================================
639
The ``InterObject`` provides for two-way `multiple dispatch`__: matching
640
up for example a source and destination repository to find the right way
641
to transfer data between them.
643
.. __: http://en.wikipedia.org/wiki/Multiple_dispatch
645
There is a subclass ``InterObject`` classes for each type of object that is
646
dispatched this way, e.g. ``InterRepository``. Calling ``.get()`` on this
647
class will return an ``InterObject`` instance providing the best match for
648
those parameters, and this instance then has methods for operations
651
inter = InterRepository.get(source_repo, target_repo)
652
inter.fetch(revision_id)
654
``InterRepository`` also acts as a registry-like object for its
655
subclasses, and they can be added through ``.register_optimizer``. The
656
right one to run is selected by asking each class, in reverse order of
657
registration, whether it ``.is_compatible`` with the relevant objects.
662
To make startup time faster, we use the ``bzrlib.lazy_import`` module to
663
delay importing modules until they are actually used. ``lazy_import`` uses
664
the same syntax as regular python imports. So to import a few modules in a
667
from bzrlib.lazy_import import lazy_import
668
lazy_import(globals(), """
677
revision as _mod_revision,
679
import bzrlib.transport
683
At this point, all of these exist as a ``ImportReplacer`` object, ready to
684
be imported once a member is accessed. Also, when importing a module into
685
the local namespace, which is likely to clash with variable names, it is
686
recommended to prefix it as ``_mod_<module>``. This makes it clearer that
687
the variable is a module, and these object should be hidden anyway, since
688
they shouldn't be imported into other namespaces.
690
While it is possible for ``lazy_import()`` to import members of a module
691
when using the ``from module import member`` syntax, it is recommended to
692
only use that syntax to load sub modules ``from module import submodule``.
693
This is because variables and classes can frequently be used without
694
needing a sub-member for example::
696
lazy_import(globals(), """
697
from module import MyClass
701
return isinstance(x, MyClass)
703
This will incorrectly fail, because ``MyClass`` is a ``ImportReplacer``
704
object, rather than the real class.
706
It also is incorrect to assign ``ImportReplacer`` objects to other variables.
707
Because the replacer only knows about the original name, it is unable to
708
replace other variables. The ``ImportReplacer`` class will raise an
709
``IllegalUseOfScopeReplacer`` exception if it can figure out that this
710
happened. But it requires accessing a member more than once from the new
711
variable, so some bugs are not detected right away.
717
The null revision is the ancestor of all revisions. Its revno is 0, its
718
revision-id is ``null:``, and its tree is the empty tree. When referring
719
to the null revision, please use ``bzrlib.revision.NULL_REVISION``. Old
720
code sometimes uses ``None`` for the null revision, but this practice is
724
Object string representations
725
=============================
727
Python prints objects using their ``__repr__`` method when they are
728
written to logs, exception tracebacks, or the debugger. We want
729
objects to have useful representations to help in determining what went
732
If you add a new class you should generally add a ``__repr__`` method
733
unless there is an adequate method in a parent class. There should be a
736
Representations should typically look like Python constructor syntax, but
737
they don't need to include every value in the object and they don't need
738
to be able to actually execute. They're to be read by humans, not
739
machines. Don't hardcode the classname in the format, so that we get the
740
correct value if the method is inherited by a subclass. If you're
741
printing attributes of the object, including strings, you should normally
742
use ``%r`` syntax (to call their repr in turn).
744
Try to avoid the representation becoming more than one or two lines long.
745
(But balance this against including useful information, and simplicity of
748
Because repr methods are often called when something has already gone
749
wrong, they should be written somewhat more defensively than most code.
750
The object may be half-initialized or in some other way in an illegal
751
state. The repr method shouldn't raise an exception, or it may hide the
752
(probably more useful) underlying exception.
757
return '%s(%r)' % (self.__class__.__name__,
764
A bare ``except`` statement will catch all exceptions, including ones that
765
really should terminate the program such as ``MemoryError`` and
766
``KeyboardInterrupt``. They should rarely be used unless the exception is
767
later re-raised. Even then, think about whether catching just
768
``Exception`` (which excludes system errors in Python2.5 and later) would
775
All code should be exercised by the test suite. See `Guide to Testing
776
Bazaar <../../developers/testing.html>`_ for detailed information about writing tests.
844
Processing Command Lines
845
------------------------
847
bzrlib has a standard framework for parsing command lines and calling
848
processing routines associated with various commands. See builtins.py
849
for numerous examples.
852
Standard Parameter Types
853
------------------------
855
There are some common requirements in the library: some parameters need to be
856
unicode safe, some need byte strings, and so on. At the moment we have
857
only codified one specific pattern: Parameters that need to be unicode
858
should be checked via ``bzrlib.osutils.safe_unicode``. This will coerce the
859
input into unicode in a consistent fashion, allowing trivial strings to be
860
used for programmer convenience, but not performing unpredictably in the
861
presence of different locales.
867
(The strategy described here is what we want to get to, but it's not
868
consistently followed in the code at the moment.)
870
bzrlib is intended to be a generically reusable library. It shouldn't
871
write messages to stdout or stderr, because some programs that use it
872
might want to display that information through a GUI or some other
875
We can distinguish two types of output from the library:
877
1. Structured data representing the progress or result of an
878
operation. For example, for a commit command this will be a list
879
of the modified files and the finally committed revision number
882
These should be exposed either through the return code or by calls
883
to a callback parameter.
885
A special case of this is progress indicators for long-lived
886
operations, where the caller should pass a ProgressBar object.
888
2. Unstructured log/debug messages, mostly for the benefit of the
889
developers or users trying to debug problems. This should always
890
be sent through ``bzrlib.trace`` and Python ``logging``, so that
891
it can be redirected by the client.
893
The distinction between the two is a bit subjective, but in general if
894
there is any chance that a library would want to see something as
895
structured data, we should make it so.
897
The policy about how output is presented in the text-mode client
898
should be only in the command-line tool.
901
Progress and Activity Indications
902
---------------------------------
904
bzrlib has a way for code to display to the user that stuff is happening
905
during a long operation. There are two particular types: *activity* which
906
means that IO is happening on a Transport, and *progress* which means that
907
higher-level application work is occurring. Both are drawn together by
910
Transport objects are responsible for calling `report_transport_activity`
913
Progress uses a model/view pattern: application code acts on a
914
`ProgressTask` object, which notifies the UI when it needs to be
915
displayed. Progress tasks form a stack. To create a new progress task on
916
top of the stack, call `bzrlib.ui.ui_factory.nested_progress_bar()`, then
917
call `update()` on the returned ProgressTask. It can be updated with just
918
a text description, with a numeric count, or with a numeric count and
919
expected total count. If an expected total count is provided the view
920
can show the progress moving along towards the expected total.
922
The user should call `finish` on the `ProgressTask` when the logical
923
operation has finished, so it can be removed from the stack.
925
Progress tasks have a complex relatioship with generators: it's a very
926
good place to use them, but because python2.4 does not allow ``finally``
927
blocks in generators it's hard to clean them up properly. In this case
928
it's probably better to have the code calling the generator allocate a
929
progress task for its use and then call `finalize` when it's done, which
930
will close it if it was not already closed. The generator should also
931
finish the progress task when it exits, because it may otherwise be a long
932
time until the finally block runs.
938
Bazaar has online help for various topics through ``bzr help COMMAND`` or
939
equivalently ``bzr command -h``. We also have help on command options,
940
and on other help topics. (See ``help_topics.py``.)
942
As for python docstrings, the first paragraph should be a single-sentence
943
synopsis of the command.
945
The help for options should be one or more proper sentences, starting with
946
a capital letter and finishing with a full stop (period).
948
All help messages and documentation should have two spaces between
952
Handling Errors and Exceptions
953
==============================
955
Commands should return non-zero when they encounter circumstances that
956
the user should really pay attention to - which includes trivial shell
959
Recommended values are:
962
1. Conflicts in merge-like operations, or changes are present in
963
diff-like operations.
964
2. Unrepresentable diff changes (i.e. binary files that we cannot show
966
3. An error or exception has occurred.
967
4. An internal error occurred (one that shows a traceback.)
969
Errors are handled through Python exceptions. Exceptions should be defined
970
inside bzrlib.errors, so that we can see the whole tree at a glance.
972
We broadly classify errors as either being either internal or not,
973
depending on whether ``internal_error`` is set or not. If we think it's our
974
fault, we show a backtrace, an invitation to report the bug, and possibly
975
other details. This is the default for errors that aren't specifically
976
recognized as being caused by a user error. Otherwise we show a briefer
977
message, unless -Derror was given.
979
Many errors originate as "environmental errors" which are raised by Python
980
or builtin libraries -- for example IOError. These are treated as being
981
our fault, unless they're caught in a particular tight scope where we know
982
that they indicate a user errors. For example if the repository format
983
is not found, the user probably gave the wrong path or URL. But if one of
984
the files inside the repository is not found, then it's our fault --
985
either there's a bug in bzr, or something complicated has gone wrong in
986
the environment that means one internal file was deleted.
988
Many errors are defined in ``bzrlib/errors.py`` but it's OK for new errors
989
to be added near the place where they are used.
991
Exceptions are formatted for the user by conversion to a string
992
(eventually calling their ``__str__`` method.) As a convenience the
993
``._fmt`` member can be used as a template which will be mapped to the
994
error's instance dict.
996
New exception classes should be defined when callers might want to catch
997
that exception specifically, or when it needs a substantially different
1000
#. If it is something that a caller can recover from, a custom exception
1003
#. If it is a data consistency issue, using a builtin like
1004
``ValueError``/``TypeError`` is reasonable.
1006
#. If it is a programmer error (using an api incorrectly)
1007
``AssertionError`` is reasonable.
1009
#. Otherwise, use ``BzrError`` or ``InternalBzrError``.
1011
Exception strings should start with a capital letter and should not have a
1012
final fullstop. If long, they may contain newlines to break the text.
1018
Do not use the Python ``assert`` statement, either in tests or elsewhere.
1019
A source test checks that it is not used. It is ok to explicitly raise
1024
* It makes the behaviour vary depending on whether bzr is run with -O
1025
or not, therefore giving a chance for bugs that occur in one case or
1026
the other, several of which have already occurred: assertions with
1027
side effects, code which can't continue unless the assertion passes,
1028
cases where we should give the user a proper message rather than an
1030
* It's not that much shorter than an explicit if/raise.
1031
* It tends to lead to fuzzy thinking about whether the check is
1032
actually needed or not, and whether it's an internal error or not
1033
* It tends to cause look-before-you-leap patterns.
1034
* It's unsafe if the check is needed to protect the integrity of the
1036
* It tends to give poor messages since the developer can get by with
1037
no explanatory text at all.
1038
* We can't rely on people always running with -O in normal use, so we
1039
can't use it for tests that are actually expensive.
1040
* Expensive checks that help developers are better turned on from the
1041
test suite or a -D flag.
1042
* If used instead of ``self.assert*()`` in tests it makes them falsely pass with -O.
362
1045
Documenting Changes
363
1046
===================
685
1375
how to set it up and configure it.
1384
Of the many workflows supported by Bazaar, the one adopted for Bazaar
1385
development itself is known as "Decentralized with automatic gatekeeper".
1386
To repeat the explanation of this given on
1387
http://bazaar-vcs.org/Workflows:
1390
In this workflow, each developer has their own branch or
1391
branches, plus read-only access to the mainline. A software gatekeeper
1392
(e.g. PQM) has commit rights to the main branch. When a developer wants
1393
their work merged, they request the gatekeeper to merge it. The gatekeeper
1394
does a merge, a compile, and runs the test suite. If the code passes, it
1395
is merged into the mainline.
1397
In a nutshell, here's the overall submission process:
1399
#. get your work ready (including review except for trivial changes)
1400
#. push to a public location
1401
#. ask PQM to merge from that location
1404
At present, PQM always takes the changes to merge from a branch
1405
at a URL that can be read by it. For Bazaar, that means a public,
1406
typically http, URL.
1408
As a result, the following things are needed to use PQM for submissions:
1410
#. A publicly available web server
1411
#. Your OpenPGP key registered with PQM (contact RobertCollins for this)
1412
#. The PQM plugin installed and configured (not strictly required but
1413
highly recommended).
1416
Selecting a Public Branch Location
1417
----------------------------------
1419
If you don't have your own web server running, branches can always be
1420
pushed to Launchpad. Here's the process for doing that:
1422
Depending on your location throughout the world and the size of your
1423
repository though, it is often quicker to use an alternative public
1424
location to Launchpad, particularly if you can set up your own repo and
1425
push into that. By using an existing repo, push only needs to send the
1426
changes, instead of the complete repository every time. Note that it is
1427
easy to register branches in other locations with Launchpad so no benefits
1428
are lost by going this way.
1431
For Canonical staff, http://people.ubuntu.com/~<user>/ is one
1432
suggestion for public http branches. Contact your manager for information
1433
on accessing this system if required.
1435
It should also be noted that best practice in this area is subject to
1436
change as things evolve. For example, once the Bazaar smart server on
1437
Launchpad supports server-side branching, the performance situation will
1438
be very different to what it is now (Jun 2007).
1441
Configuring the PQM Plug-In
1442
---------------------------
1444
While not strictly required, the PQM plugin automates a few things and
1445
reduces the chance of error. Before looking at the plugin, it helps to
1446
understand a little more how PQM operates. Basically, PQM requires an
1447
email indicating what you want it to do. The email typically looks like
1450
star-merge source-branch target-branch
1454
star-merge http://bzr.arbash-meinel.com/branches/bzr/jam-integration http://bazaar-vcs.org/bzr/bzr.dev
1456
Note that the command needs to be on one line. The subject of the email
1457
will be used for the commit message. The email also needs to be ``gpg``
1458
signed with a key that PQM accepts.
1460
The advantages of using the PQM plugin are:
1462
#. You can use the config policies to make it easy to set up public
1463
branches, so you don't have to ever type the full paths you want to merge
1466
#. It checks to make sure the public branch last revision matches the
1467
local last revision so you are submitting what you think you are.
1469
#. It uses the same public_branch and smtp sending settings as bzr-email,
1470
so if you have one set up, you have the other mostly set up.
1472
#. Thunderbird refuses to not wrap lines, and request lines are usually
1473
pretty long (you have 2 long URLs in there).
1475
Here are sample configuration settings for the PQM plugin. Here are the
1476
lines in bazaar.conf::
1479
email = Joe Smith <joe.smith@internode.on.net>
1480
smtp_server=mail.internode.on.net:25
1482
And here are the lines in ``locations.conf`` (or ``branch.conf`` for
1483
dirstate-tags branches)::
1485
[/home/joe/bzr/my-integration]
1486
push_location = sftp://joe-smith@bazaar.launchpad.net/%7Ejoe-smith/bzr/my-integration/
1487
push_location:policy = norecurse
1488
public_branch = http://bazaar.launchpad.net/~joe-smith/bzr/my-integration/
1489
public_branch:policy = appendpath
1490
pqm_email = Bazaar PQM <pqm@bazaar-vcs.org>
1491
pqm_branch = http://bazaar-vcs.org/bzr/bzr.dev
1493
Note that the push settings will be added by the first ``push`` on
1494
a branch. Indeed the preferred way to generate the lines above is to use
1495
``push`` with an argument, then copy-and-paste the other lines into
1502
Here is one possible recipe once the above environment is set up:
1504
#. pull bzr.dev => my-integration
1505
#. merge patch => my-integration
1506
#. fix up any final merge conflicts (NEWS being the big killer here).
1512
The ``push`` step is not required if ``my-integration`` is a checkout of
1515
Because of defaults, you can type a single message into commit and
1516
pqm-commit will reuse that.
1519
Tracking Change Acceptance
1520
--------------------------
1522
The web interface to PQM is https://pqm.bazaar-vcs.org/. After submitting
1523
a change, you can visit this URL to confirm it was received and placed in
1526
When PQM completes processing a change, an email is sent to you with the
1530
Reviewing Blueprints
1531
====================
1533
Blueprint Tracking Using Launchpad
1534
----------------------------------
1536
New features typically require a fair amount of discussion, design and
1537
debate. For Bazaar, that information is often captured in a so-called
1538
"blueprint" on our Wiki. Overall tracking of blueprints and their status
1539
is done using Launchpad's relevant tracker,
1540
https://blueprints.launchpad.net/bzr/. Once a blueprint for ready for
1541
review, please announce it on the mailing list.
1543
Alternatively, send an email begining with [RFC] with the proposal to the
1544
list. In some cases, you may wish to attach proposed code or a proposed
1545
developer document if that best communicates the idea. Debate can then
1546
proceed using the normal merge review processes.
1549
Recording Blueprint Review Feedback
1550
-----------------------------------
1552
Unlike its Bug Tracker, Launchpad's Blueprint Tracker doesn't currently
1553
(Jun 2007) support a chronological list of comment responses. Review
1554
feedback can either be recorded on the Wiki hosting the blueprints or by
1555
using Launchpad's whiteboard feature.
689
1558
Planning Releases
690
1559
=================
1562
Using Releases and Milestones in Launchpad
1563
------------------------------------------
1565
TODO ... (Exact policies still under discussion)
added
removed
doc/en/developer-guide/HACKING.txt
