If you’re going to be doing development on Twisted itself, or if you want to take advantage of bleeding-edge features (or bug fixes) that are not yet available in a numbered release, you’ll probably want to check out a tree from the Twisted Subversion repository. The Trunk is where all current development takes place.
This document lists some useful tips for working on this cutting edge.
Subversion tutorials can be found elsewhere, see in particular the Subversion homepage . The relevant data you need to check out a copy of the Twisted tree is available on the development page , and is as follows:
$ svn co svn://svn.twistedmatrix.com/svn/Twisted/trunk Twisted
By using svn co svn://svn.twistedmatrix.com/svn/Twisted/trunk otherdir , you can put the workspace tree in a directory other than “Twisted” . I do this (with a name like “Twisted-Subversion” ) to remind myself that this tree comes from Subversion and not from a released version (like “Twisted-1.0.5” ). This practice can cause a few problems, because there are a few places in the Twisted tree that need to know where the tree starts, so they can add it to sys.path without requiring the user manually set their PYTHONPATH. These functions walk the current directory up to the root, looking for a directory named “Twisted” (sometimes exactly that, sometimes with a .startswith test). Generally these are test scripts or other administrative tools which expect to be launched from somewhere inside the tree (but not necessarily from the top).
If you rename the tree to something other than Twisted , these tools may wind up trying to use Twisted source files from /usr/lib/python2.5 or elsewhere on the default sys.path . Normally this won’t matter, but it is good to be aware of the issue in case you run into problems.
twisted/test/process_twisted.py is one of these programs.
In order to simplify the use of Subversion, we typically use Divmod Combinator . You may find it to be useful, too. In particular, because Twisted uses branches for almost all feature development, if you plan to contribute to Twisted you will probably find Combinator very useful. For more details, see the Combinator website, as well as the UQDS page.
There are currently several C extension modules in Twisted: twisted.internet.cfsupport , twisted.internet.iocpreactor._iocp , and twisted.python._epoll . These modules are optional, but you’ll have to compile them if you want to experience their features, performance improvements, or bugs. There are two approaches.
The first is to do a regular distutils ./setup.py build , which will create a directory under build/ to hold both the generated .so files as well as a copy of the 600-odd .py files that make up Twisted. If you do this, you will need to set your PYTHONPATH to something like MyDir/Twisted/build/lib.linux-i686-2.5 in order to run code against the Subversion twisted (as opposed to whatever’s installed in /usr/lib/python2.5 or wherever python usually looks). In addition, you will need to re-run the build command every time you change a .py file. The build/lib.foo directory is a copy of the main tree, and that copy is only updated when you re-run setup.py build . It is easy to forget this and then wonder why your code changes aren’t being expressed.
The second technique is to build the C modules in place, and point your PYTHONPATH at the top of the tree, like MyDir/Twisted . This way you’re using the .py files in place too, removing the confusion a forgotten rebuild could cause with the separate build/ directory above. To build the C modules in place, do ./setup.py build_ext -i . You only need to re-run this command when you change the C files. Note that setup.py is not Make, it does not always get the dependencies right (.h files in particular), so if you are hacking on the cReactor you may need to manually delete the .o files before doing a rebuild. Also note that doing a setup.py clean will remove the .o files but not the final .so files, they must be deleted by hand.
To run the full unit-test suite, do:
To run a single test file (like twisted/test/test_defer.py ), do one of:
To run any tests that are related to a code file, like twisted/protocols/imap4.py , do:
./bin/trial --testmodule twisted/mail/imap4.py
This depends upon the .py file having an appropriate “test-case-name” tag that indicates which test cases provide coverage. See the Test Standards document for details about using “test-case-name” . In this example, the twisted.mail.test.test_imap test will be run.
Many tests create temporary files in /tmp or ./_trial_temp, but everything in /tmp should be deleted when the test finishes. Sometimes these cleanup calls are commented out by mistake, so if you see a stray /email@example.com directory, it is probably from test_dirdbm or test_popsicle . Look for an rmtree that has been commented out and complain to the last developer who touched that file.
Twisted documentation (not including the automatically-generated API docs) is in Lore Format . These .xhtml files are translated into .html files by the “bin/lore/lore” script, which can check the files for syntax problems (hlint), process multiple files at once, insert the files into a template before processing, and can also translate the files into LaTeX or PostScript instead.
To build the HTML form of the howto/ docs, do the following. Note that the index file will be placed in doc/core/howto/index.html .
./bin/lore/lore -p --config template=doc/core/howto/template.tpl doc/core/howto/*.xhtml
To run hlint over a single Lore document, such as doc/development/policy/svn-dev.xhtml , do the following. This is useful because the HTML conversion may bail without a useful explanation if it sees mismatched tags.
./bin/lore/lore -n --output lint doc/development/policy/svn-dev.xhtml
To convert it to HTML (including markup, interpolation of examples, footnote processing, etc), do the following. The results will be placed in doc/development/policy/svn-dev.html :
./bin/lore/lore -p --config template=doc/core/howto/template.tpl \ doc/development/policy/svn-dev.xhtml
Note that hyperlinks to other documents may not be quite right unless you include a “-l” argument to bin/lore/lore . Links in the .xhtml file are to .xhtml targets: when the .xhtml is turned into .html, the link targets are supposed to be turned into .html also. In addition to this, Lore markup of the form <code class="API"> is supposed to turn into a link to the corresponding API reference page. These links will probably be wrong unless the correct base URL is provided to Lore.
Twisted uses a customized trac-post-commit-hook to enable ticket updates based on svn commit logs. When making a branch for a ticket, the branch name should end in -<ticket number> , for example my-branch-9999 . This will add a ticket comment containing a changeset link and branch name. To make your commit message show up as a comment on a Trac ticket, add a refs #<ticket number> line at the bottom of your commit message. To automatically close a ticket on Trac as Fixed and add a comment with the closing commit message, add a Fixes: #<ticket number> line to your commit message. In general, a commit message closing a ticket looks like this:
Merge my-branch-9999: A single-line summary. Author: jesstess Reviewers: exarkun, glyph Fixes: #9999 My longer description of the changes made.
The Twisted Coding Standard elaborates on commit messages and source control.
A minor mode for development with Twisted using Emacs is available. See twisted-dev.el , provided by twisted-emacs , for several utility functions which make it easier to grep for methods, run test cases, etc.