How to develop Trac with Eclipse PyDev

Follow the instructions for Setting up the environment and Installing and configuring Trac on the Developer setup for Trac page, before configuring Eclipse and PyDev.

Installing and configuring Eclipse

1. Install ​Eclipse (3.3 or newer will do).
2. Install the ​PyDev plugin for Eclipse.
3. Alternatively, install ​LiClipse, it comes with PyDev already integrated.
4. (Optional) Install either ​Subclipse or ​Subversive for Eclipse-integrated Subversion tools.
5. Create a new project in Eclipse that contains the sources for Trac.
6. In Eclipse, make sure that the PYTHONPATH in the project properties dialog includes the sources for Trac and for Genshi.
7. Create an initial run configuration by clicking right on trac/web/standalone.py file, and choosing Run As → Python Run. Trac will complain that no environment has been set.
8. Select Run → Open Run Dialog… and set the correct command line arguments in the arguments tab, eg. —port 8000 /path/to/myproject.
   • Note that the option —auto-reload will cause tracd to restart every time source code has been changed, but it seems to prevent debugging with PyDev. This seems to have something to do with the way Trac reloads new instance as a child thread using "thread" library, which doesn't seem to be compatible with PyDev debugging. Then, instead of using "thread"-module you should use "threading"-module (higherlevel).
   • Note that if your debugging doesn't work with a plugin, then remove the package from the install destination, eg rm -Rf and soft link it from your source.
9. You should now be able to run tracd, as well as to debug it using the same run configuration. To run the test cases, just click on a test folder and select Run → Python unit tests.

Automatic translation compilation

If you want to set up automatic translation compilation do the following:

1. Right click on Trac project and select Properties. Select Builders. Click New. Select Program.
2. Name builder, like 'Locale fi_FI builder'.
3. Main tab:
   • Location: click Browse File System…. Select Python executable.
   • Working Directory: set it to ${project_loc}.
   • Arguments: setup.py compile_catalog -f -l fi_FI (change to your locale).
4. Refresh tab:
   • Check Refresh resources upon completion.
   • Select Spesific resources and select trac/locale/fi_FI (select your locale).
5. Build Options tab:
   • Check During auto builds.
   • Check Specify working set of relevant resources.
   • Click Specify resources…. Select trac/locale/fi_FI (select your locale, same as in step 4).
   • Name it like fi_FI locale.
6. After modifying your message.po file you should get following output:

    running compile_catalog
    compiling catalog 'trac/locale\\fi_FI\\LC_MESSAGES\\messages.po' to 'trac/locale\\fi_FI\\LC_MESSAGES\\messages.mo'
   

If Trac is running, your changes will be effective immediately.

pylint integration

PyLint is a validator and quality checker for the Python programming language. It can be integrated with PyDev, see ​pydev.org for details.

For developing Trac plugins, you should reference to all dependent eggs, such as Trac, Genshi, Babel, etc. To do this open Project > Properties, go to node PyDev - PYTHONPATH and click on Add zip/jar/egg/ in tab External Libraries. Search for your Trac-$VERSION-.egg and do the same for all required libraries (Genshi, Babel).

If you import from pkg_resources you need to add #@UnresolvedImport after it, because otherwise you get the error: Unresolved import: resource_filename. See ​stackoverflow-question for details:

from pkg_resources import resource_filename #@UnresolvedImport

Ignoring warnings

As described in ​stackoverflow you can use a "deactivation comment" at the end of the line, if you want to suppress a warning. Examples:

from pkg_resources import resource_filename  # @UnresolvedImport
fpath, fname = os.path.split(name)  # @UnusedVariable

You can also configure PyDev to avoid getting a warning "unused variable", see ​PyDev Code Analysis.

Format Code

To enable Code Formatting using PEP8 (command "Format Code", short cut Ctrl + Shift + F) you need to check Preferences → PyDev/Editor/CodeStyle/CodeFormatter and activate "Using autopep8.py for code formatting".

Remote Debugging

With Eclipse ​PyDev it is possible to debug Trac remotely. This means you can evaluate all variables and "Step into" (F5), "Step over" (F6) and "Step out" (F7) of each line of code.

How to setup the remote debugger is described in ​PyDev Manual. Basically you need to follow these steps:

1. Go to the debug perspective.
2. Start the remote debugger server.
3. Make sure pydevd.py is in your pythonpath: the python file usually resides under eclipse/plugins/org.python.pydev_x.x.x/pysrc/pydevd.py.

Then you can insert the following code to start the debug mode (see Screenshot​):

try: import pydevd;pydevd.settrace() #@UnresolvedImport
except ImportError: None # avoids throwing an Exception when not in debug mode

Acknowledgements

Originally these instructions were ​posted on trac-dev list by Joachim Hoessler.