1
============================
2
Guidelines for modifying bzr
3
============================
7
(The current version of this document is available in the file ``HACKING``
8
in the source tree, or at http://bazaar-ng.org/hacking.html)
13
* New functionality should have test cases. Preferably write the
14
test before writing the code.
16
In general, you can test at either the command-line level or the
17
internal API level. See Writing Tests below for more detail.
19
* Try to practice Test-Driven Development. before fixing a bug, write a
20
test case so that it does not regress. Similarly for adding a new
21
feature: write a test case for a small version of the new feature before
22
starting on the code itself. Check the test fails on the old code, then
23
add the feature or fix and check it passes.
25
* Exceptions should be defined inside bzrlib.errors, so that we can
26
see the whole tree at a glance.
28
* Imports should be done at the top-level of the file, unless there is
29
a strong reason to have them lazily loaded when a particular
30
function runs. Import statements have a cost, so try to make sure
31
they don't run inside hot functions.
33
* Module names should always be given fully-qualified,
34
i.e. ``bzrlib.hashcache`` not just ``hashcache``.
36
* Commands should return non-zero when they encounter circumstances that
37
the user should really pay attention to - which includes trivial shell
40
Recommended values are
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1- Conflicts in merge-like operations, or changes are present in
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2- Unrepresentable diff changes (i.e. binary files that we cannot show
46
3- An error or exception has occurred.
51
We have a commitment to 6 months API stability - any supported symbol in a
52
release of bzr MUST NOT be altered in any way that would result in
5
This document describes the Bazaar internals and the development process.
6
It's meant for people interested in developing Bazaar, and some parts will
7
also be useful to people developing Bazaar plugins.
9
If you have any questions or something seems to be incorrect, unclear or
10
missing, please talk to us in ``irc://irc.freenode.net/#bzr``, or write to
11
the Bazaar mailing list. To propose a correction or addition to this
12
document, send a merge request or new text to the mailing list.
14
The latest developer documentation can be found online at
15
http://doc.bazaar.canonical.com/developers/.
20
Exploring the Bazaar Platform
21
=============================
23
Before making changes, it's a good idea to explore the work already
24
done by others. Perhaps the new feature or improvement you're looking
25
for is available in another plug-in already? If you find a bug,
26
perhaps someone else has already fixed it?
28
To answer these questions and more, take a moment to explore the
29
overall Bazaar Platform. Here are some links to browse:
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* The Plugins page on the Wiki - http://wiki.bazaar.canonical.com/BzrPlugins
33
* The Bazaar product family on Launchpad - https://launchpad.net/bazaar
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* Bug Tracker for the core product - https://bugs.launchpad.net/bzr/
37
If nothing else, perhaps you'll find inspiration in how other developers
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have solved their challenges.
40
Finding Something To Do
41
=======================
43
Ad-hoc performance work can also be done. One useful tool is the 'evil' debug
44
flag. For instance running ``bzr -Devil commit -m "test"`` will log a backtrace
45
to the bzr log file for every method call which triggers a slow or non-scalable
46
part of the bzr library. So checking that a given command with ``-Devil`` has
47
no backtraces logged to the log file is a good way to find problem function
48
calls that might be nested deep in the code base.
50
Planning and Discussing Changes
51
===============================
53
There is a very active community around Bazaar. Mostly we meet on IRC
54
(#bzr on irc.freenode.net) and on the mailing list. To join the Bazaar
55
community, see http://wiki.bazaar.canonical.com/BzrSupport.
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If you are planning to make a change, it's a very good idea to mention it
58
on the IRC channel and/or on the mailing list. There are many advantages
59
to involving the community before you spend much time on a change.
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* you get to build on the wisdom of others, saving time
64
* if others can direct you to similar code, it minimises the work to be done
66
* it assists everyone in coordinating direction, priorities and effort.
68
In summary, maximising the input from others typically minimises the
69
total effort required to get your changes merged. The community is
70
friendly, helpful and always keen to welcome newcomers.
73
Bazaar Development in a Nutshell
74
================================
76
.. was from http://wiki.bazaar.canonical.com/BzrGivingBack
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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.
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First, get a local copy of the development mainline (See `Why make a local
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$ bzr branch lp:bzr bzr.dev
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Now make your own branch::
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$ bzr branch bzr.dev 123456-my-bugfix
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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!).
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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
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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
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$ bzr push lp:~<your_lp_username>/bzr/meaningful_name_here
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After you have pushed your branch, you will need to propose it for merging to
123
the Bazaar trunk. Go to
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<https://launchpad.net/~<your_lp_username>/bzr/meaningful_name_here> and choose
125
"Propose for merging into another branch". Select "lp:bzr" to hand
126
your changes off to the Bazaar developers for review and merging.
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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?
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---------------------------------
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:
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- ``bzr diff -r ancestor:...``
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- 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::
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$ bzr branch bzr.dev additional_fixes
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$ cd additional_fixes # hack, hack, hack
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Understanding the Development Process
185
=====================================
187
The development team follows many practices including:
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* a public roadmap and planning process in which anyone can participate
191
* time based milestones everyone can work towards and plan around
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* extensive code review and feedback to contributors
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* complete and rigorous test coverage on any code contributed
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* automated validation that all tests still pass before code is merged
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into the main code branch.
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The key tools we use to enable these practices are:
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* Launchpad - https://launchpad.net/
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* Bazaar - http://bazaar.canonical.com/
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* Patch Queue Manager - https://launchpad.net/pqm/
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For further information, see <http://wiki.bazaar.canonical.com/BzrDevelopment>.
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Preparing a Sandbox for Making Changes to Bazaar
214
================================================
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Bazaar supports many ways of organising your work. See
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http://wiki.bazaar.canonical.com/SharedRepositoryLayouts for a summary of the
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popular alternatives.
220
Of course, the best choice for you will depend on numerous factors:
221
the number of changes you may be making, the complexity of the changes, etc.
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As a starting suggestion though:
224
* create a local copy of the main development branch (bzr.dev) by using
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bzr branch lp:bzr bzr.dev
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* keep your copy of bzr.dev pristine (by not developing in it) and keep
230
it up to date (by using bzr pull)
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* create a new branch off your local bzr.dev copy for each issue
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(bug or feature) you are working on.
235
This approach makes it easy to go back and make any required changes
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after a code review. Resubmitting the change is then simple with no
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risk of accidentally including edits related to other issues you may
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be working on. After the changes for an issue are accepted and merged,
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the associated branch can be deleted or archived as you wish.
242
Navigating the Code Base
243
========================
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.
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This file covers a brief introduction to Bazaar and lists some of its
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Installs Bazaar system-wide or to your home directory. To perform
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development work on Bazaar it is not required to run this file - you
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can simply run the bzr command from the top level directory of your
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development copy. Note: That if you run setup.py this will create a
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'build' directory in your development branch. There's nothing wrong
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with this but don't be confused by it. The build process puts a copy
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of the main code base into this build directory, along with some other
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files. You don't need to go in here for anything discussed in this
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Possibly the most exciting folder of all, bzrlib holds the main code
270
base. This is where you will go to edit python files and contribute to
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Holds documentation on a whole range of things on Bazaar from the
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origination of ideas within the project to information on Bazaar
276
features and use cases. Within this directory there is a subdirectory
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for each translation into a human language. All the documentation
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is in the ReStructuredText markup language.
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Documentation specifically targeted at Bazaar and plugin developers.
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(Including this document.)
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doc/en/release-notes/
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Detailed changes in each Bazaar release (there is one file by series:
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bzr-2.3.txt, bzr-2.4.txt, etc) that can affect users or plugin
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High-level summaries of changes in each Bazaar release (there is one
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file by series: whats-new-in-2.3.txt, whats-new-in-2.4.txt, etc).
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Automatically-generated API reference information is available at
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<http://starship.python.net/crew/mwh/bzrlibapi/>.
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See also the `Bazaar Architectural Overview
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<http://doc.bazaar.canonical.com/developers/overview.html>`_.
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We don't change APIs in stable branches: any supported symbol in a stable
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release of bzr must not be altered in any way that would result in
53
311
breaking existing code that uses it. That means that method names,
54
312
parameter ordering, parameter names, variable and attribute names etc must
55
313
not be changed without leaving a 'deprecated forwarder' behind. This even
56
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applies to modules and classes.
58
316
If you wish to change the behaviour of a supported API in an incompatible
59
way, you need to change its name as well. For instance, if I add a optional keyword
317
way, you need to change its name as well. For instance, if I add an optional keyword
60
318
parameter to branch.commit - that's fine. On the other hand, if I add a
61
319
keyword parameter to branch.commit which is a *required* transaction
62
object, I should rename the API - i.e. to 'branch.commit_transaction'.
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object, I should rename the API - i.e. to 'branch.commit_transaction'.
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(Actually, that may break code that provides a new implementation of
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``commit`` and doesn't expect to receive the parameter.)
64
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When renaming such supported API's, be sure to leave a deprecated_method (or
65
326
_function or ...) behind which forwards to the new API. See the
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327
bzrlib.symbol_versioning module for decorators that take care of the
67
328
details for you - such as updating the docstring, and issuing a warning
68
when the old api is used.
329
when the old API is used.
70
For unsupported API's, it does not hurt to follow this discipline, but its
331
For unsupported API's, it does not hurt to follow this discipline, but it's
71
332
not required. Minimally though, please try to rename things so that
72
333
callers will at least get an AttributeError rather than weird results.
75
Standard parameter types
76
------------------------
78
There are some common requirements in the library: some parameters need to be
79
unicode safe, some need byte strings, and so on. At the moment we have
80
only codified one specific pattern: Parameters that need to be unicode
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should be check via 'bzrlib.osutils.safe_unicode'. This will coerce the
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input into unicode in a consistent fashion, allowing trivial strings to be
83
used for programmer convenience, but not performing unpredictably in the
84
presence of different locales.
89
If you change the behaviour of a command, please update its docstring
90
in bzrlib/commands.py. This is displayed by the 'bzr help' command.
95
If you make a user-visible change, please add a note to the NEWS file.
96
The description should be written to make sense to someone who's just
97
a user of bzr, not a developer: new functions or classes shouldn't be
98
mentioned, but new commands, changes in behaviour or fixed nontrivial
99
bugs should be listed. See the existing entries for an idea of what
102
Within each release, entries in the news file should have the most
103
user-visible changes first. So the order should be approximately:
105
* changes to existing behaviour - the highest priority because the
106
user's existing knowledge is incorrect
107
* new features - should be brought to their attention
108
* bug fixes - may be of interest if the bug was affecting them, and
109
should include the bug number if any
110
* major documentation changes
111
* changes to internal interfaces
113
People who made significant contributions to each change are listed in
114
parenthesis. This can include reporting bugs (particularly with good
115
details or reproduction recipes), submitting patches, etc.
120
Functions, methods, classes and modules should have docstrings
121
describing how they are used.
123
The first line of the docstring should be a self-contained sentence.
125
For the special case of Command classes, this acts as the user-visible
126
documentation shown by the help command.
128
The docstrings should be formatted as reStructuredText_ (like this
129
document), suitable for processing using the epydoc_ tool into HTML
132
.. _reStructuredText: http://docutils.sourceforge.net/rst.html
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.. _epydoc: http://epydoc.sourceforge.net/
140
Please write PEP-8__ compliant code.
142
One often-missed requirement is that the first line of docstrings
143
should be a self-contained one-sentence summary.
145
__ http://www.python.org/peps/pep-0008.html
152
Functions, methods or members that are in some sense "private" are given
153
a leading underscore prefix. This is just a hint that code outside the
154
implementation should probably not use that interface.
156
We prefer class names to be concatenated capital words (``TestCase``)
157
and variables, methods and functions to be lowercase words joined by
158
underscores (``revision_id``, ``get_revision``).
160
For the purposes of naming some names are treated as single compound
161
words: "filename", "revno".
163
Consider naming classes as nouns and functions/methods as verbs.
169
``revision_id`` not ``rev_id`` or ``revid``
171
Functions that transform one thing to another should be named ``x_to_y``
172
(not ``x2y`` as occurs in some old code.)
178
Python destructors (``__del__``) work differently to those of other
179
languages. In particular, bear in mind that destructors may be called
180
immediately when the object apparently becomes unreferenced, or at some
181
later time, or possibly never at all. Therefore we have restrictions on
182
what can be done inside them.
184
0. Never use a __del__ method without asking Martin/Robert first.
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1. Never rely on a ``__del__`` method running. If there is code that
187
must run, do it from a ``finally`` block instead.
189
2. Never ``import`` from inside a ``__del__`` method, or you may crash the
192
3. In some places we raise a warning from the destructor if the object
193
has not been cleaned up or closed. This is considered OK: the warning
194
may not catch every case but it's still useful sometimes.
200
In some places we have variables which point to callables that construct
201
new instances. That is to say, they can be used a lot like class objects,
202
but they shouldn't be *named* like classes:
204
> I think that things named FooBar should create instances of FooBar when
205
> called. Its plain confusing for them to do otherwise. When we have
206
> something that is going to be used as a class - that is, checked for via
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> isinstance or other such idioms, them I would call it foo_class, so that
208
> it is clear that a callable is not sufficient. If it is only used as a
209
> factory, then yes, foo_factory is what I would use.
215
(The strategy described here is what we want to get to, but it's not
216
consistently followed in the code at the moment.)
218
bzrlib is intended to be a generically reusable library. It shouldn't
219
write messages to stdout or stderr, because some programs that use it
220
might want to display that information through a GUI or some other
223
We can distinguish two types of output from the library:
225
1. Structured data representing the progress or result of an
226
operation. For example, for a commit command this will be a list
227
of the modified files and the finally committed revision number
230
These should be exposed either through the return code or by calls
231
to a callback parameter.
233
A special case of this is progress indicators for long-lived
234
operations, where the caller should pass a ProgressBar object.
236
2. Unstructured log/debug messages, mostly for the benefit of the
237
developers or users trying to debug problems. This should always
238
be sent through ``bzrlib.trace`` and Python ``logging``, so that
239
it can be redirected by the client.
241
The distinction between the two is a bit subjective, but in general if
242
there is any chance that a library would want to see something as
243
structured data, we should make it so.
245
The policy about how output is presented in the text-mode client
246
should be only in the command-line tool.
251
In general tests should be placed in a file named test_FOO.py where
252
FOO is the logical thing under test. That file should be placed in the
253
tests subdirectory under the package being tested.
255
For example, tests for merge3 in bzrlib belong in bzrlib/tests/test_merge3.py.
256
See bzrlib/selftest/test_sampler.py for a template test script.
258
Tests can be written for the UI or for individual areas of the library.
259
Choose whichever is appropriate: if adding a new command, or a new command
260
option, then you should be writing a UI test. If you are both adding UI
261
functionality and library functionality, you will want to write tests for
262
both the UI and the core behaviours. We call UI tests 'blackbox' tests
263
and they are found in bzrlib/tests/blackbox/*.py.
265
When writing blackbox tests please honour the following conventions:
267
1. Place the tests for the command 'name' in
268
bzrlib/tests/blackbox/test_name.py. This makes it easy for developers
269
to locate the test script for a faulty command.
271
2. Use the 'self.run_bzr("name")' utility function to invoke the command
272
rather than running bzr in a subprocess or invoking the
273
cmd_object.run() method directly. This is a lot faster than
274
subprocesses and generates the same logging output as running it in a
275
subprocess (which invoking the method directly does not).
277
3. Only test the one command in a single test script. Use the bzrlib
278
library when setting up tests and when evaluating the side-effects of
279
the command. We do this so that the library api has continual pressure
280
on it to be as functional as the command line in a simple manner, and
281
to isolate knock-on effects throughout the blackbox test suite when a
282
command changes it name or signature. Ideally only the tests for a
283
given command are affected when a given command is changed.
287
Currently, bzr selftest is used to invoke tests.
288
You can provide a pattern argument to run a subset. For example,
289
to run just the blackbox tests, run::
291
./bzr selftest -v blackbox
294
Errors and exceptions
295
=====================
297
Errors are handled through Python exceptions. They can represent user
298
errors, environmental errors or program bugs. Sometimes we can't be sure
299
at the time it's raised which case applies. See bzrlib/errors.py for
300
details on the error-handling practices.
336
Deprecation decorators
337
----------------------
339
``bzrlib.symbol_versioning`` provides decorators that can be attached to
340
methods, functions, and other interfaces to indicate that they should no
341
longer be used. For example::
343
@deprecated_method(deprecated_in((0, 1, 4)))
345
return self._new_foo()
347
To deprecate a static method you must call ``deprecated_function``
348
(**not** method), after the staticmethod call::
351
@deprecated_function(deprecated_in((0, 1, 4)))
352
def create_repository(base, shared=False, format=None):
354
When you deprecate an API, you should not just delete its tests, because
355
then we might introduce bugs in them. If the API is still present at all,
356
it should still work. The basic approach is to use
357
``TestCase.applyDeprecated`` which in one step checks that the API gives
358
the expected deprecation message, and also returns the real result from
359
the method, so that tests can keep running.
361
Deprecation warnings will be suppressed for final releases, but not for
362
development versions or release candidates, or when running ``bzr
363
selftest``. This gives developers information about whether their code is
364
using deprecated functions, but avoids confusing users about things they
374
The copyright policy for bzr was recently made clear in this email (edited
375
for grammatical correctness)::
377
The attached patch cleans up the copyright and license statements in
378
the bzr source. It also adds tests to help us remember to add them
379
with the correct text.
381
We had the problem that lots of our files were "Copyright Canonical
382
Development Ltd" which is not a real company, and some other variations
383
on this theme. Also, some files were missing the GPL statements.
385
I want to be clear about the intent of this patch, since copyright can
386
be a little controversial.
388
1) The big motivation for this is not to shut out the community, but
389
just to clean up all of the invalid copyright statements.
391
2) It has been the general policy for bzr that we want a single
392
copyright holder for all of the core code. This is following the model
393
set by the FSF, which makes it easier to update the code to a new
394
license in case problems are encountered. (For example, if we want to
395
upgrade the project universally to GPL v3 it is much simpler if there is
396
a single copyright holder). It also makes it clearer if copyright is
397
ever debated, there is a single holder, which makes it easier to defend
398
in court, etc. (I think the FSF position is that if you assign them
399
copyright, they can defend it in court rather than you needing to, and
400
I'm sure Canonical would do the same).
401
As such, Canonical has requested copyright assignments from all of the
404
3) If someone wants to add code and not attribute it to Canonical, there
405
is a specific list of files that are excluded from this check. And the
406
test failure indicates where that is, and how to update it.
408
4) If anyone feels that I changed a copyright statement incorrectly, just
409
let me know, and I'll be happy to correct it. Whenever you have large
410
mechanical changes like this, it is possible to make some mistakes.
412
Just to reiterate, this is a community project, and it is meant to stay
413
that way. Core bzr code is copyright Canonical for legal reasons, and
414
the tests are just there to help us maintain that.
423
Bazaar has a few facilities to help debug problems by going into pdb_, the
426
.. _pdb: http://docs.python.org/lib/debugger-commands.html
428
If the ``BZR_PDB`` environment variable is set
429
then bzr will go into pdb post-mortem mode when an unhandled exception
432
If you send a SIGQUIT or SIGBREAK signal to bzr then it will drop into the
433
debugger immediately. SIGQUIT can be generated by pressing Ctrl-\\ on
434
Unix. SIGBREAK is generated with Ctrl-Pause on Windows (some laptops have
435
this as Fn-Pause). You can continue execution by typing ``c``. This can
436
be disabled if necessary by setting the environment variable
437
``BZR_SIGQUIT_PDB=0``.
439
All tests inheriting from bzrlib.tests.TestCase can use ``self.debug()``
440
instead of the longer ``import pdb; pdb.set_trace()``. The former also works
441
when ``stdin/stdout`` are redirected (by using the original ``stdin/stdout``
442
file handles at the start of the ``bzr`` script) while the later doesn't.
443
``bzrlib.debug.set_trace()`` also uses the original ``stdin/stdout`` file
449
Bazaar accepts some global options starting with ``-D`` such as
450
``-Dhpss``. These set a value in `bzrlib.debug.debug_flags`, and
451
typically cause more information to be written to the trace file. Most
452
`mutter` calls should be guarded by a check of those flags so that we
453
don't write out too much information if it's not needed.
455
Debug flags may have effects other than just emitting trace messages.
457
Run ``bzr help global-options`` to see them all.
459
These flags may also be set as a comma-separated list in the
460
``debug_flags`` option in e.g. ``~/.bazaar/bazaar.conf``. (Note that it
461
must be in this global file, not in the branch or location configuration,
462
because it's currently only loaded at startup time.) For instance you may
463
want to always record hpss traces and to see full error tracebacks::
465
debug_flags = hpss, error
309
474
indexes into the branch's revision history.
315
The ``Transport`` layer handles access to local or remote directories.
316
Each Transport object acts like a logical connection to a particular
317
directory, and it allows various operations on files within it. You can
318
*clone* a transport to get a new Transport connected to a subdirectory or
321
Transports are not used for access to the working tree. At present
322
working trees are always local and they are accessed through the regular
323
Python file io mechanisms.
328
Transports work in URLs. Take note that URLs are by definition only
329
ASCII - the decision of how to encode a Unicode string into a URL must be
330
taken at a higher level, typically in the Store. (Note that Stores also
331
escape filenames which cannot be safely stored on all filesystems, but
332
this is a different level.)
334
The main reason for this is that it's not possible to safely roundtrip a
335
URL into Unicode and then back into the same URL. The URL standard
336
gives a way to represent non-ASCII bytes in ASCII (as %-escapes), but
337
doesn't say how those bytes represent non-ASCII characters. (They're not
338
guaranteed to be UTF-8 -- that is common but doesn't happen everywhere.)
340
For example if the user enters the url ``http://example/%e0`` there's no
341
way to tell whether that character represents "latin small letter a with
342
grave" in iso-8859-1, or "latin small letter r with acute" in iso-8859-2
343
or malformed UTF-8. So we can't convert their URL to Unicode reliably.
345
Equally problematic if we're given a url-like string containing non-ascii
346
characters (such as the accented a) we can't be sure how to convert that
347
to the correct URL, because we don't know what encoding the server expects
348
for those characters. (Although this is not totally reliable we might still
349
accept these and assume they should be put into UTF-8.)
351
A similar edge case is that the url ``http://foo/sweet%2Fsour" contains
352
one directory component whose name is "sweet/sour". The escaped slash is
353
not a directory separator. If we try to convert URLs to regular Unicode
354
paths this information will be lost.
356
This implies that Transports must natively deal with URLs; for simplicity
357
they *only* deal with URLs and conversion of other strings to URLs is done
358
elsewhere. Information they return, such as from ``list_dir``, is also in
359
the form of URL components.
365
If you'd like to propose a change, please post to the
366
bazaar-ng@lists.canonical.com list with a patch, bzr changeset, or link to a
367
branch. Please put '[patch]' in the subject so we can pick them out, and
368
include some text explaining the change. Remember to put an update to the NEWS
369
file in your diff, if it makes any changes visible to users or plugin
370
developers. Please include a diff against mainline if you're giving a link to
373
Please indicate if you think the code is ready to merge, or if it's just a
374
draft or for discussion. If you want comments from many developers rather than
375
to be merged, you can put '[rfc]' in the subject lines.
377
Anyone is welcome to review code. There are broadly three gates for
380
* Doesn't reduce test coverage: if it adds new methods or commands,
381
there should be tests for them. There is a good test framework
382
and plenty of examples to crib from, but if you are having trouble
383
working out how to test something feel free to post a draft patch
386
* Doesn't reduce design clarity, such as by entangling objects
387
we're trying to separate. This is mostly something the more
388
experienced reviewers need to help check.
390
* Improves bugs, features, speed, or code simplicity.
392
Code that goes in should pass all three.
394
If you read a patch please reply and say so. We can use a numeric scale
395
of -1, -0, +0, +1, meaning respectively "really don't want it in current
396
form", "somewhat uncomfortable", "ok with me", and "please put it in".
397
Anyone can "vote". (It's not really voting, just a terse expression.)
399
If something gets say two +1 votes from core reviewers, and no
400
vetos, then it's OK to come in. Any of the core developers can bring it
401
into their integration branch, which I'll merge regularly. (If you do
402
so, please reply and say so.)
477
Unicode and Encoding Support
478
============================
480
This section discusses various techniques that Bazaar uses to handle
481
characters that are outside the ASCII set.
486
When a ``Command`` object is created, it is given a member variable
487
accessible by ``self.outf``. This is a file-like object, which is bound to
488
``sys.stdout``, and should be used to write information to the screen,
489
rather than directly writing to ``sys.stdout`` or calling ``print``.
490
This file has the ability to translate Unicode objects into the correct
491
representation, based on the console encoding. Also, the class attribute
492
``encoding_type`` will effect how unprintable characters will be
493
handled. This parameter can take one of 3 values:
496
Unprintable characters will be represented with a suitable replacement
497
marker (typically '?'), and no exception will be raised. This is for
498
any command which generates text for the user to review, rather than
499
for automated processing.
500
For example: ``bzr log`` should not fail if one of the entries has text
501
that cannot be displayed.
504
Attempting to print an unprintable character will cause a UnicodeError.
505
This is for commands that are intended more as scripting support, rather
506
than plain user review.
507
For example: ``bzr ls`` is designed to be used with shell scripting. One
508
use would be ``bzr ls --null --unknowns | xargs -0 rm``. If ``bzr``
509
printed a filename with a '?', the wrong file could be deleted. (At the
510
very least, the correct file would not be deleted). An error is used to
511
indicate that the requested action could not be performed.
514
Do not attempt to automatically convert Unicode strings. This is used
515
for commands that must handle conversion themselves.
516
For example: ``bzr diff`` needs to translate Unicode paths, but should
517
not change the exact text of the contents of the files.
520
``bzrlib.urlutils.unescape_for_display``
521
----------------------------------------
523
Because Transports work in URLs (as defined earlier), printing the raw URL
524
to the user is usually less than optimal. Characters outside the standard
525
set are printed as escapes, rather than the real character, and local
526
paths would be printed as ``file://`` URLs. The function
527
``unescape_for_display`` attempts to unescape a URL, such that anything
528
that cannot be printed in the current encoding stays an escaped URL, but
529
valid characters are generated where possible.
535
We write some extensions in C using pyrex. We design these to work in
538
* User with no C compiler
539
* User with C compiler
542
The recommended way to install bzr is to have a C compiler so that the
543
extensions can be built, but if no C compiler is present, the pure python
544
versions we supply will work, though more slowly.
546
For developers we recommend that pyrex be installed, so that the C
547
extensions can be changed if needed.
549
For the C extensions, the extension module should always match the
550
original python one in all respects (modulo speed). This should be
551
maintained over time.
553
To create an extension, add rules to setup.py for building it with pyrex,
554
and with distutils. Now start with an empty .pyx file. At the top add
555
"include 'yourmodule.py'". This will import the contents of foo.py into this
556
file at build time - remember that only one module will be loaded at
557
runtime. Now you can subclass classes, or replace functions, and only your
558
changes need to be present in the .pyx file.
560
Note that pyrex does not support all 2.4 programming idioms, so some
561
syntax changes may be required. I.e.
563
- 'from foo import (bar, gam)' needs to change to not use the brackets.
564
- 'import foo.bar as bar' needs to be 'import foo.bar; bar = foo.bar'
566
If the changes are too dramatic, consider
567
maintaining the python code twice - once in the .pyx, and once in the .py,
568
and no longer including the .py file.
571
Making Installers for OS Windows
572
================================
573
To build a win32 installer, see the instructions on the wiki page:
574
http://wiki.bazaar.canonical.com/BzrWin32Installer
582
What is a Core Developer?
583
-------------------------
585
While everyone in the Bazaar community is welcome and encouraged to
586
propose and submit changes, a smaller team is reponsible for pulling those
587
changes together into a cohesive whole. In addition to the general developer
588
stuff covered above, "core" developers have responsibility for:
592
* managing releases (see `Releasing Bazaar <http://doc.bazaar.canonical.com/developers/releasing.html>`_)
595
Removing barriers to community participation is a key reason for adopting
596
distributed VCS technology. While DVCS removes many technical barriers,
597
a small number of social barriers are often necessary instead.
598
By documenting how the above things are done, we hope to
599
encourage more people to participate in these activities, keeping the
600
differences between core and non-core contributors to a minimum.
603
Communicating and Coordinating
604
------------------------------
606
While it has many advantages, one of the challenges of distributed
607
development is keeping everyone else aware of what you're working on.
608
There are numerous ways to do this:
610
#. Assign bugs to yourself in Launchpad
611
#. Mention it on the mailing list
614
As well as the email notifcations that occur when merge requests are sent
615
and reviewed, you can keep others informed of where you're spending your
616
energy by emailing the **bazaar-commits** list implicitly. To do this,
617
install and configure the Email plugin. One way to do this is add these
618
configuration settings to your central configuration file (e.g.
619
``~/.bazaar/bazaar.conf``)::
622
email = Joe Smith <joe.smith@internode.on.net>
623
smtp_server = mail.internode.on.net:25
625
Then add these lines for the relevant branches in ``locations.conf``::
627
post_commit_to = bazaar-commits@lists.canonical.com
628
post_commit_mailer = smtplib
630
While attending a sprint, RobertCollins' Dbus plugin is useful for the
631
same reason. See the documentation within the plugin for information on
632
how to set it up and configure it.
643
Keeping on top of bugs reported is an important part of ongoing release
644
planning. Everyone in the community is welcome and encouraged to raise
645
bugs, confirm bugs raised by others, and nominate a priority. Practically
646
though, a good percentage of bug triage is often done by the core
647
developers, partially because of their depth of product knowledge.
649
With respect to bug triage, core developers are encouraged to play an
650
active role with particular attention to the following tasks:
652
* keeping the number of unconfirmed bugs low
653
* ensuring the priorities are generally right (everything as critical - or
654
medium - is meaningless)
655
* looking out for regressions and turning those around sooner rather than later.
658
As well as prioritizing bugs and nominating them against a
659
target milestone, Launchpad lets core developers offer to mentor others in
added
removed
doc/developers/HACKING.txt
