from Common import *
from MiscUtils.PropertiesObject import PropertiesObject
class PlugInError(Exception):
pass
class PlugIn(Object):
"""Template for Webware Plug-ins.
A plug-in is a software component that is loaded by WebKit in order to
provide additional WebKit functionality without necessarily having to modify
WebKit's source. The most infamous plug-in is PSP (Python Server Pages)
which ships with Webware.
Plug-ins often provide additional servlet factories, servlet subclasses,
examples and documentation. Ultimately, it is the plug-in author's choice
as to what to provide and in what manner.
Instances of this class represent plug-ins which are ultimately Python
packages (see the Python Tutorial, 6.4: "Packages" at
http://docs.python.org/tut/node8.html#SECTION008400000000000000000).
A plug-in must also be a Webware component which means that it will have
a Properties.py file advertising its name, version, requirements, etc.
You can ask a plug-in for its properties().
The plug-in/package must have an __init__.py while must contain a function:
def InstallInWebKit(appServer):
This function is invoked to take whatever actions are needed to plug the
new component into WebKit. See PSP for an example.
If you ask an AppServer for its plugIns(), you will get a list of instances
of this class.
The path of the plug-in is added to sys.path, if it's not already there.
This is convenient, but we may need a more sophisticated solution in the
future to avoid name collisions between plug-ins.
Note that this class is hardly ever subclassed. The software in the
plug-in package is what provides new functionality and there is currently
no way to tell AppServer to use custom subclasses of this class on a
case-by-case basis (and so far there is currently no need).
Instructions for invoking:
p = PlugIn(self, '../Foo') # 'self' is typically AppServer. It gets passed to InstallInWebKit()
willNotLoadReason = plugIn.load()
if willNotLoadReason:
print ' Plug-in %s cannot be loaded because:\n %s' % (path, willNotLoadReason)
return None
p.install()
# Note that load() and install() could raise exceptions. You should expect this.
"""
def __init__(self, appServer, path):
"""Initializes the plug-in with basic information.
This lightweight constructor does not access the file system.
"""
self._appServer = appServer
self._path = path
self._dir, self._name = os.path.split(path)
self._cacheDir = os.path.join(
self._appServer.application()._cacheDir, self._name)
self._ver = '(unknown)'
self._docs = self._docContext = None
self._examplePages = self._examplePagesContext = None
def load(self):
"""Loads the plug-in into memory, but does not yet install it.
Will return None on success, otherwise a message (string) that says
why the plug-in could not be loaded.
"""
print 'Loading plug-in: %s at %s' % (self._name, self._path)
assert os.path.exists(self._path)
self._properties = PropertiesObject(self.serverSidePath('Properties.py'))
if not self._properties['willRun']:
return self._properties['willNotRunReason']
if not self._dir in sys.path:
sys.path.append(self._dir)
self._module = __import__(self._name, globals(), [], [])
if not hasattr(self._module, 'InstallInWebKit'):
raise PlugInError, \
"Plug-in '%s' in '%s' has no InstallInWebKit() function." \
% (self._name, self._dir)
setattr(self._module, 'plugIn', self)
if not os.path.exists(self._cacheDir):
os.mkdir(self._cacheDir)
self.setUpDocContext()
self.setUpExamplePages()
def setUpDocContext(self):
"""Add a context for the documentation."""
app = self._appServer.application()
if app.hasContext('Docs'):
self._docs = self._properties.get('docs', None) or None
if self.hasDocs():
docsPath = self.serverSidePath('Docs')
assert os.path.exists(docsPath), \
'Plug-in %s says it has documentation, ' \
'but there is no Docs/ subdir.' % self._name
if os.path.exists(os.path.join(docsPath, '__init__.py')):
ctxName = self._name + '/Docs'
if not app.hasContext(ctxName):
app.addContext(ctxName, docsPath)
self._docContext = ctxName
else:
print 'Cannot create Docs context for plug-in %s' \
' (no __init__.py found).' % self._name
def setUpExamplePages(self):
"""Add a context for the examples."""
app = self._appServer.application()
if app.hasContext('Examples'):
config = self._properties.get('WebKitConfig', {})
self._examplePages = config.get('examplePages', None) or None
if self.hasExamplePages():
examplesPath = self.serverSidePath('Examples')
assert os.path.exists(examplesPath), \
'Plug-in %s says it has example pages, ' \
'but there is no Examples/ subdir.' % self._name
if os.path.exists(os.path.join(examplesPath, '__init__.py')):
ctxName = self._name + '/Examples'
if not app.hasContext(ctxName):
app.addContext(ctxName, examplesPath)
self._examplePagesContext = ctxName
else:
print 'Cannot create Examples context for plug-in %s' \
' (no __init__.py found).' % self._name
def docs(self):
return self._docs
def hasDocs(self):
return self._docs is not None
def docsContext(self):
return self._docsContext
def examplePages(self):
return self._examplePages
def hasExamplePages(self):
return self._examplePages is not None
def examplePagesContext(self):
return self._examplePagesContext
def install(self):
"""Install plug-in by invoking its required InstallInWebKit function."""
self._module.InstallInWebKit(self._appServer)
def name(self):
"""Return the name of the plug-in. Example: 'Foo'"""
return self._name
def directory(self):
"""Return the directory in which the plug-in resides. Example: '..'"""
return self._dir
def path(self):
"""Return the full path of the plug-in. Example: '../Foo'"""
return self._path
def serverSidePath(self, path=None):
if path:
return os.path.normpath(os.path.join(self._path, path))
else:
return self._path
def module(self):
"""Return the Python module object of the plug-in."""
return self._module
def properties(self):
"""Return the properties.
This is a dictionary-like object, of the plug-in which comes
from its Properties.py file. See MiscUtils.PropertiesObject.py.
"""
return self._properties