# Working from Twisted's Subversion repository

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.

## Checkout

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 pserver page, and is as follows:

    $ svn co svn://svn.twistedmatrix.com/svn/Twisted/trunk Twisted

## Alternate tree names

By using `cvs checkout -d foo Twisted`, 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/python2.2 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.

## Compiling C extensions

There are currently 3 C extension modules in Twisted: twisted.internet.cReactor, twisted.runner.portmap, and twisted.spread.cBanana . 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-i686-2.2` in order to run code against the Subversion twisted (as opposed to whatever's installed in `/usr/lib/python2.2` 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.

## Running tests

To run the full unit-test suite, do:

    ./bin/trial -v twisted.test

To run a single test file (like `twisted/test/test_defer.py`), do one of:

    ./bin/trial -v twisted.test.test_defer

or

    ./bin/trial -v twisted/test/test_defer.py

To run any tests that are related to a code file, like `twisted/protocols/imap4.py`, do:

    ./bin/trial -v --testmodule twisted/protocols/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.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 /tmp/@12345.1 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.

## Admin scripts

The `admin/` directory holds several administrative tools, some of which are used when turning a Subversion checkout into a full numbered release.

## Building docs

Twisted documentation (not including the automatically-generated API docs) is in Lore Format. These `.html` files are translated into `.xhtml` files by the bin/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 generate the full documentation set, run the `admin/process-docs` shell script. This will create processed HTML, man pages, and 250-page book.pdf file containing all the docs rolled into a single nicely-formatted volume. This script needs several helper tools to handle the images and the LaTeX conversion: debian packages tetex-extra, netpbm, and gs-common should be sufficient. The docs-build process currently takes about 3 minutes on the twistedmatrix.com build machine.

To build just the HTML form of the howto/ docs, do a subset of the work done in `admin/process-docs`, such as the following. Note that the index file will be placed in `doc/howto/index.xhtml`.

    ./bin/lore -p --config template=doc/howto/template.tpl doc/howto/*.html

To run hlint over a single Lore document, such as `doc/howto/cvs-dev.html`, do the following. This is useful because the HTML conversion may bail without a useful explanation if it sees mismatched tags.

    ./bin/lore -n --output lint doc/howto/cvs-dev.html

To convert it to HTML (including markup, interpolation of examples, footnote processing, etc), do the following. The results will be placed in `doc/howto/cvs-dev.xhtml`:

    ./bin/lore -p --config template=doc/howto/template.tpl doc/howto/cvs-dev.html

Note that hyperlinks to other documents may not be quite right unless you include a -l argument to `bin/lore`. Links in the .html file are to .html targets: when the .html is turned into .xhtml, the link targets are supposed to be turned into .xhtml 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.

## Emacs

Check out the TwistedEmacs module (which lives in the same Subversion repository, just do cvs checkout TwistedEmacs instead of cvs checkout Twisted). `twisted-dev.el` has several utility functions which make it easier to grep for methods, run test cases, process Lore documents, etc.

## Building Debian packages

Running debuild -uc -us from the top of the Subversion tree will (hopefully) result in a collection of .deb packages in the tree's parent directory. This requires other tools to be installed (devscripts for one), and requires that admin/process-docs be run first. The .debs created will have a version number based upon whatever is at the top of `debian/changelog`, which is generally only updated when an official release is made, so be careful that you don't create confusingly-numbered package files.