Egg cooking

Since Trac 0.11, Genshi is used as the new template engine. Some APIs have also been changed.

This tutorial shows how to make an egg, and load an egg in Trac. In the advanced parts you'll learn how to serve templates and static content from an egg.

You should be familiar with ​component architecture and ​plugin development. This plugin is based on the example in the plugin development article. Here we extend it a bit further.

Required items

• setuptools>=0.6b1. For instructions and files see ​EasyInstall page.
• Trac 0.11. Download it from the ​TracDownload page.
• Genshi>-0.4. Download it from the ​GenshiDownload page.

Directories

To develop a plugin you need to create a few directories to keep things together.

So let's create following directories:

./helloworld-plugin/
./helloworld-plugin/helloworld/

Main plugin

The first step is to generate the main module for this plugin. We will construct a simple plugin that will display "Hello world!" on the screen when accessed through the /helloworld URL. The plugin also provides a "Hello" button that is, by default, rendered on the far right in the main navigation bar.

So create helloworld.py in ./helloworld-plugin/helloworld/:

# Helloworld plugin

import re

from genshi.builder import tag

from trac.core import *
from trac.web import IRequestHandler
from trac.web.chrome import INavigationContributor

class HelloWorldPlugin(Component):
    implements(INavigationContributor, IRequestHandler)

    # INavigationContributor methods
    def get_active_navigation_item(self, req):
        return 'helloworld'
    
    def get_navigation_items(self, req):
        yield ('mainnav', 'helloworld',
               tag.a('Hello World', href=req.href.helloworld()))
    
    # IRequestHandler methods
    def match_request(self, req):
        return re.match(r'/helloworld(?:_trac)?(?:/.*)?$', req.path_info)
    
    def process_request(self, req):
        req.send_response(200)
        req.send_header('Content-Type', 'text/plain')
        req.end_headers()
        req.write('Hello world!')

To help understand how that works, read the ​INavigationContributor and ​IRequestHandler interface specifications.

Make it a module

To make the plugin a module, you simply create an __init__.py in ./helloworld-plugin/helloworld/:

# Helloworld module
from helloworld import *

Make it an egg

Now it's time to make it an egg. For that we need a chicken called setup.py in ./helloworld-plugin/:

from setuptools import find_packages, setup

# name can be any name.  This name will be used to create .egg file.
# name that is used in packages is the one that is used in the trac.ini file.
# use package name as entry_points
setup(
    name='Trachelloworld', version='1.1',
    packages=find_packages(exclude=['*.tests*']),
    entry_points = """
        [trac.plugins]
        helloworld = helloworld
    """,
)

You done need to add special ​egg metadata in Trac 0.11.

First deployment

Now try to build the plugin. Run the command python setup.py bdist_egg in the directory where you created it. If everything went OK you should have a .egg file in ./dist directory. Copy this .egg file to /[your trac env]/plugins directory.

During development you can run the command python setup.py develop in the directory where you created it. This way you don't need to do it every time you change the code. Check ​TracDev/PluginDevelopment for more deployment options.

Restart the trac server. If you're using mod_python you have to restart Apache.

Now you should see Hello World link at far right in main navigation bar when accessing your site. Click it.

Aftermath

Now you have successfully created your first egg. You can continue further to learn how to use templates in your plugins, and make its output look like other Trac pages.

TagIt(khundeen)?