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Post-rendering Resource Inclusion

Project Description

The resource library is a Zope 3 extension that is designed to make the inclusion of JavaScript, CSS, and other resources easy, cache-friendly, and component-friendly.

Resource Library

The resource library is designed to make the inclusion of JavaScript, CSS, and other resources easy, cache-friendly, and component-friendly. For instance, if two widgets on a page need the same JavaScript library, the library should be only loaded once, but the widget designers should not have to concern themselves with the presence of other widgets.

Imagine that one widget has a copy of a fictional Javascript library. To configure that library as available use ZCML like this:

>>> zcml("""
... <configure
...     xmlns="http://namespaces.zope.org/zope"
...     package="zc.resourcelibrary">
...   <include package="." file="meta.zcml" />
...   <resourceLibrary name="some-library">
...     <directory source="tests/example"/>
...   </resourceLibrary>
...
... </configure>
... """)

This is exactly equivalent to a resourceDirectory tag, with no additional effect.

Loading Files

It is also possible to indicate that one or more Javascript or CSS files should be included (by reference) into the HTML of a page that needs the library. This is the current difference between resourceLibrary and resourceDirectory.

>>> zcml("""
... <configure
...     xmlns="http://namespaces.zope.org/zope"
...     package="zc.resourcelibrary">
...   <include package="." file="meta.zcml" />
...   <resourceLibrary name="my-lib">
...     <directory
...         source="tests/example/my-lib"
...         include="included.js included.css included.kss"
...     />
...   </resourceLibrary>
...
... </configure>
... """)

If a file is included that the resource library doesn’t understand (i.e. it isn’t Javascript or CSS), an exception will occur.

>>> zcml("""
... <configure
...     xmlns="http://namespaces.zope.org/zope"
...     package="zc.resourcelibrary">
...   <include package="." file="meta.zcml" />
...   <resourceLibrary name="bad-lib">
...     <directory
...         source="tests/example/my-lib"
...         include="included.bad"
...     />
...   </resourceLibrary>
...
... </configure>
... """)
Traceback (most recent call last):
...
ZopeXMLConfigurationError:...
    ConfigurationError: Resource library doesn't know how to include this file: "included.bad".

Usage

Components signal their need for a particular resource library (Javascript or otherwise) by using a special TAL expression. (The use of replace is not mandated, the result may be assigned to a dummy variable, or otherwise ignored.)

>>> zpt('<tal:block replace="resource_library:my-lib"/>')

We’ll be using a testbrowser.Browser to simulate a user viewing web pages.

>>> from zope.testbrowser.wsgi import Browser
>>> browser = Browser()
>>> browser.addHeader('Authorization', 'Basic mgr:mgrpw')
>>> browser.handleErrors = False

When a page is requested that does not need any resource libraries, the HTML will be untouched.

>>> browser.open('http://localhost/zc.resourcelibrary.test_template_1')
>>> browser.contents
'...<head></head>...'

When a page is requested that uses a component that needs a resource library, the library will be referenced in the rendered page.

>>> browser.open('http://localhost/zc.resourcelibrary.test_template_2')

A reference to the JavaScript is inserted into the HTML.

>>> '/@@/my-lib/included.js' in browser.contents
True

And the JavaScript is available from the URL referenced.

>>> browser.open('/@@/my-lib/included.js')
>>> browser.headers['Content-Type']
'application/javascript'
>>> print(browser.contents.decode('ascii'))
    function be_annoying() {
    alert('Hi there!');
}

For inclusion of resources the full base url with namespaces is used.

>>> browser.open('http://localhost/++skin++Basic/zc.resourcelibrary.test_template_2')
>>> print(browser.contents)
<html...
src="http://localhost/++skin++Basic/@@/my-lib/included.js"...
</html>

A reference to the CSS is also inserted into the HTML.

>>> browser.open('http://localhost/zc.resourcelibrary.test_template_2')
>>> '/@@/my-lib/included.css' in browser.contents
True

And the CSS is available from the URL referenced.

>>> browser.open('/@@/my-lib/included.css')
>>> browser.headers['Content-Type']
'text/css'
>>> print(browser.contents.decode('ascii'))
div .border {
    border: 1px silid black;
}

A reference to an unknown library causes an exception.

>>> browser.open('http://localhost/zc.resourcelibrary.test_template_3')
Traceback (most recent call last):
...
RuntimeError: Unknown resource library: "does-not-exist"

Library usage may also be signaled programattically. For example, if a page would not otherwise include a resource library…

>>> page = ('<html><head></head>'
...         '<body tal:define="unused view/doSomething">'
...         'This is the body.</body>')
>>> class View(object):
...     context = getRootFolder()
...     def doSomething(self):
...         pass
>>> zpt(page, view=View())
'...<head></head>...'

If we then programmatically indicate that a resource library is needed, it will be included.

>>> import zc.resourcelibrary
>>> class View(object):
...     context = getRootFolder()
...     def doSomething(self):
...         zc.resourcelibrary.need('my-lib')
>>> '/@@/my-lib/included.js' in zpt(page, view=View())
True

Content-type checking

Resources should be referenced only from HTML and XML content, other content types should not be touched by the resource library:

>>> page = ('<html><head>'
...         '<tal:block replace="resource_library:my-lib"/>'
...         '</head><body></body></html>')
>>> '/@@/my-lib/included.js' in zpt(page, content_type='text/html')
True
>>> '/@@/my-lib/included.js' in zpt(page, content_type='text/xml')
True
>>> '/@@/my-lib/included.js' in zpt(page, content_type='text/none')
False

This also works if the content type contains uppercase characters, as per RfC 2045 on the syntax of MIME type specifications (we can’t test uppercase characters in the major type yet since the publisher is not completely up to the RfC on that detail yet):

>>> '/@@/my-lib/included.js' in zpt(page, content_type='text/hTMl')
True
>>> '/@@/my-lib/included.js' in zpt(page, content_type='text/nOne')
False

Parameters to the content type can’t fool the check either:

>>> '/@@/my-lib/included.js' in zpt(
...     page, content_type='text/xml; charset=utf-8')
True
>>> '/@@/my-lib/included.js' in zpt(
...     page, content_type='text/none; charset=utf-8')
False

The content type is, however, assumed to be a strictly valid MIME type specification, implying that it can’t contain any whitespace up to the semicolon signalling the start of parameters, if any (we can’t test whitespace around the major type as that would already upset the publisher):

>>> '/@@/my-lib/included.js' in zpt(
...     page, content_type='text/ xml')
False
>>> '/@@/my-lib/included.js' in zpt(
...     page, content_type='text/xml ; charset=utf-8')
False

The content type may also be None if it was never set, which of course doesn’t count as HTML or XML either:

>>> from zc.resourcelibrary import publication
>>> from io import BytesIO
>>> request = publication.Request(body_instream=BytesIO(), environ={})
>>> request.response.setResult("This is not HTML text.")
>>> b'/@@/my-lib/included.js' in request.response.consumeBody()
False

Dependencies

If a resource library registers a dependency on another library, the dependency must be satisfied or an error will be generated.

>>> zcml("""
... <configure
...     xmlns="http://namespaces.zope.org/zope"
...     package="zc.resourcelibrary">
...   <include package="." file="meta.zcml" />
...
...   <resourceLibrary name="dependent-but-unsatisfied" require="not-here">
...     <directory source="tests/example"/>
...   </resourceLibrary>
...
... </configure>
... """)
Traceback (most recent call last):
...
ConfigurationExecutionError:...Resource library "dependent-but-unsatisfied" has unsatisfied dependency on "not-here"...
...

When the dependencies are satisfied, the registrations will succeed.

>>> zcml("""
... <configure
...     xmlns="http://namespaces.zope.org/zope"
...     package="zc.resourcelibrary">
...   <include package="." file="meta.zcml" />
...
...   <resourceLibrary name="dependent" require="dependency">
...     <directory source="tests/example" include="1.js"/>
...   </resourceLibrary>
...
...   <resourceLibrary name="dependency">
...     <directory source="tests/example" include="2.css"/>
...   </resourceLibrary>
...
... </configure>
... """)

If one library depends on another and the first library is referenced on a page, the second library will also be included in the rendered HTML.

>>> zpt('<tal:block replace="resource_library:dependent"/>')
>>> browser.open('http://localhost/zc.resourcelibrary.test_template_4')
>>> '/@@/dependent/1.js' in browser.contents
True
>>> '/@@/dependency/2.css' in browser.contents
True

Order matters, espacially for js files, so the dependency should appear before the dependent library in the page

>>> print(browser.contents.strip())
<html>...dependency/2.css...dependent/1.js...</html>

It is possible for a resource library to only register a list of dependencies and not specify any resources.

When such a library is used in a resource_library statement in a template, only its dependencies are referenced in the final rendered page.

>>> zcml("""
... <configure
...     xmlns="http://namespaces.zope.org/zope"
...     package="zc.resourcelibrary">
...   <include package="." file="meta.zcml" />
...
...   <resourceLibrary name="only_require" require="my-lib dependent"/>
...
... </configure>
... """)
>>> zpt('<tal:block replace="resource_library:only_require"/>')
>>> browser.open('http://localhost/zc.resourcelibrary.test_template_7')
>>> '/@@/my-lib/included.js' in browser.contents
True
>>> '/@@/my-lib/included.css' in browser.contents
True
>>> '/@@/dependent/1.js' in browser.contents
True
>>> '/@@/dependency/2.css' in browser.contents
True
>>> '/@@/only_require' in browser.contents
False

Error Conditions

Errors are reported if you do something wrong.

>>> zcml("""
... <configure
...     xmlns="http://namespaces.zope.org/zope"
...     package="zc.resourcelibrary">
...   <include package="." file="meta.zcml" />
...
...   <resourceLibrary name="some-library">
...     <directory source="does-not-exist"/>
...   </resourceLibrary>
...
... </configure>
... """)
Traceback (most recent call last):
...
ZopeXMLConfigurationError: ...
    ConfigurationError: Directory u'...does-not-exist' does not exist

Multiple Heads

On occasion the body of an HTML document may contain the text “<head>”. In those cases, only the actual head tag should be manipulated. The first occurrence of “<head>” has the script tag inserted…

>>> browser.open('http://localhost/zc.resourcelibrary.test_template_5')
>>> print(browser.contents)
<html>...<head> <script src="http://localhost/@@/my-lib/included.js"...

…but that is the only time it is inserted.

>>> browser.contents.count('src="http://localhost/@@/my-lib/included.js"')
1

Error during publishing

Note that in case an exception is raised during publishing, the resource library is disabled.

>>> browser.handleErrors = True
>>> browser.post(
...    'http://localhost/zc.resourcelibrary.test_template_5',
...    'value:int=dummy', 'multipart/form-data')
Traceback (most recent call last):
 ...
urllib.error.HTTPError: ...
>>> '/@@/my-lib/included.js' in browser.contents
False

Custom “directory” factories

By default, a resource directory is created when a directory directive is used. You can add a factory option to specify a different resource-directory factory. This can be used, for example, to provide dynamic resources.

>>> zcml("""
... <configure
...     xmlns="http://namespaces.zope.org/zope"
...     package="zc.resourcelibrary">
...   <include package="." file="meta.zcml" />
...
...   <resourceLibrary name="my-lib">
...     <directory
...         source="tests/example/my-lib"
...         include="foo.js"
...         factory="zc.resourcelibrary.tests.tests.TestFactory"
...     />
...   </resourceLibrary>
...
... </configure>
... """, clear=['my-lib'])

The factory will be called with a source directory, a security checker and a name. We’ve created a class that implements a resource directory dynamically.

>>> browser.open('http://localhost/zc.resourcelibrary.test_template_2')
>>> '/@@/my-lib/foo.js' in browser.contents
True
>>> browser.open('http://localhost/@@/my-lib/foo.js')
>>> print(browser.contents)
foo = 1;

Library insertion place marker

You can explicitly mark where to insert HTML. Do do that, add the special comment “<!– zc.resourcelibrary –>” (exact string, w/o quotes) to the template. It will be replaced by resource libraries HTML on processing.

>>> browser.open('http://localhost/zc.resourcelibrary.test_template_6')

A reference to the JavaScript is inserted into the HTML.

>>> print(browser.contents)
<html>
  <head>
    <title>Marker test</title>
<BLANKLINE>
    <!-- Libraries will be included below -->
    <script src="http://localhost/@@/my-lib/foo.js"
        type="text/javascript">
    </script>
  </head>
...
</html>

Future Work

  • We want to be able to specify a single file to add to the resource.
  • We may want to be able to override a file in the resource with a different file.
  • Currently only one <directory> tag is allowed per-library. If multiple tags are allowed, should they be merged or have distinct prefixes?
  • Add a test to ensure that files are only included once, and in the proper order

CHANGES

2.0.0 (2017-05-23)

  • Add support for Python 3.4, 3.5, 3.6 and PyPy.
  • Drop test dependency on zope.app.testing and zope.app.zcmlfiles, among others.
  • Make zope.app.publication dependency optional.

1.3.4 (2012-01-20)

1.3.2 (2010-08-16)

  • Response._addDependencies will only include a ResourceLibrary in the list of dependencies if the ResourceLibrary actually has included resources.

    This makes directives that simply declare dependencies on other libraries work again.

  • Add missing depedency on zope.app.pagetemplate, clean up unused imports and whitespace.

1.3.1 (2010-03-24)

  • Resource libraries that are required during a retried request are now correctly registered and injected to the HTML.
  • Import hooks functionality from zope.component after it was moved there from zope.site. This lifts the dependency on zope.site.
  • Removed an unused ISite import and thereby, the undeclared dependency on zope.location.

1.3.0 (2009-10-08)

  • Use zope.browserresource instead of zope.app.publisher, removing a dependency on latter.
  • Look up the “resources view” via queryMultiAdapter instead of looking into the adapter registry.
  • Moved the dependency on zope.site to the test dependencies.

1.2.0 (2009-06-04)

  • Use zope.site instead of zope.app.component. Removes direct dependency on zope.app.component.

1.1.0 (2009-05-05)

New features:

  • An attempt to generate resource URLs using the “resources view” (@@) is now made; if unsuccesful, we fall back to the previous method of crafting the URL by hand from the site url. This ensures that the resource library respects the existing plugging points for resource publishing (see zope.app.publisher.browser.resources).
  • You can now explicitly specify where resource links should be inserted using the special marker comment ‘<!– zc.resourcelibrary –>’.

1.0.2 (2009-01-27)

  • Remove zope.app.zapi from dependencies, substituting its uses with direct imports.
  • Use zope-dev at zope.org mailing list address instead of zope3-dev at zope.org as the latter one is retired.
  • Change “cheeseshop” to “pypi” in the package homepage.

1.0.1 (2008-03-07)

Bugs fixed:

  • added the behavior from the standard Zope 3 response to guess that a body that is not HTML without an explicit mimetype should have a ‘text/plain’ mimetype. This means that, for instance, redirects with a body of ‘’ and no explicit content type will no longer cause an exception in the resourcelibrary response code.

1.0.0 (2008-02-17)

New features:

  • You can now provide an alternative “directory-resource” factory. This facilitates implementation of dynamic resources.

Bugs fixed:

  • Updated the functional-testing zcml file to get rid of a deprecation warning.

0.8.2 (2007-12-07)

  • bug fix: when checking content type, take into account that it may be None

0.8.1 (2007-12-05)

  • changed MIME type handling to be more restrictive about whitespace to conform to RfC 2045

0.8 (2007-12-04)

  • fixed the check for HTML and XML content to allow content type parameters

0.6.1 (2007-11-03)

  • Update package meta-data.
  • Fixed package dependencies.
  • Merged functional and unit tests.

0.5.2 (2006-06-15)

  • Add more package meta-data.

0.5.1 (2006-06-06)

  • Update package code to work with newer versions of other packages.

0.5.0 (2006-04-24)

  • Initial release.
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