webresource

webresource

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A resource registry for web applications.

Webresource is a compact Python library to declare resources (primarily Javascript and CSS files) for delivery in your web application.

Features

• Declare web resources via python.
• Manage dependencies between resources.
• Grouping of resources.
• Conditional delivery of resources.
• Development and a production mode.

Detailed Documentation

The detailed webresource documentation is available here <https://webresource.readthedocs.io>_.

Source Code

The sources are in a GIT DVCS with its main branches at github <http://github.com/conestack/webresource>_.

Copyright

• Copyright (c) 2021-2022 Cone Contributors

Contributors

• Robert Niederreiter (Author)

Overview

Declaring resources

Webresource provides 3 types of resources. ScriptResource is used for registering Javascript, StyleResource for CSS files and LinkResource can be used for registering all sorts of resource links.

Declare a script:

.. code-block:: python

import webresource as wr

my_js = wr.ScriptResource(
    name='my_js',
    directory='/path/to/scripts',
    resource='my.js',
    compressed='my.min.js',
    path='js'
)

name is a unique identifier for the resource. directory defines the location in the file system where the resource can be found. resource is the default resource file corresponding to this declaration. compressed is the minified version of the resource, which gets considered if Webresource is used in production mode. path defines the path part of the URL at which this resource is published.

Dependencies between resources are defined by passing depends argument, which can be a single dependency or multiple dependencies as tuple or list:

.. code-block:: python

other_js = wr.ScriptResource(
    name='other_js',
    depends='my_js',
    ...
)

It's possible to pass a callback funtion as include argument. It can be used to calculate whether a resource should be included or not:

.. code-block:: python

def include_conditional_js():
    # Compute whether to include resource here.
    return True

conditional_js = wr.ScriptResource(
    name='conditional_js',
    include=include_conditional_js,
    ...
)

The include property can also be set as boolean which might be useful for excluding some already registered resources:

.. code-block:: python

conditional_js.include = False

Resource URLs can be rendered including a unique key of the resource file. This is useful in environments with strong caching to make sure changed resources get reloaded properly. When working with unique resource URLs, the unique key gets rendered intermediate between path and file name, thus the integrator needs to implement custom URL rewriting/dispatching/traversal for correct resource delivery:

.. code-block:: python

cached_js = wr.ScriptResource(
    name='cached_js',
    unique=True,
    unique_prefix='++webresource++',
    ...
)

If external resources should be declared, pass url argument. In this case path, resource and compressed get ignored:

.. code-block:: python

external_js = wr.ScriptResource(
    name='external_js',
    url='https://example.org/resource.js'
    ...
)

It is possible to render additional attributes on resource tags by passing additional keyword arguments to the constructor. This can be usefule when working with web compilers like Diazo.

.. code-block:: python

custom_attr_js = wr.ScriptResource(
    name='custom_attr_js',
    **{'data-bundle': 'bundle-name'}
)

This examples uses ScriptResource but the above described behavior applies to all provided Resource types.

Resource groups

Resources can be grouped by adding them to ResourceGroup objects:

.. code-block:: python

scripts = wr.ResourceGroup(name='scripts')

Resources can be added to a group at instantiation time if group is known in advance.

.. code-block:: python

script = wr.ScriptResource(
    name='script',
    group=scripts
    ...
)

or an already declared resource can be added to a group:

.. code-block:: python

scripts.add(script)

Groups can be nested:

.. code-block:: python

scripts = wr.ResourceGroup(name='scripts')
base_scripts = wr.ResourceGroup(
    name='base_scripts',
    group=scripts
)
addon_scripts = wr.ResourceGroup(
    name='addon_scripts',
    group=scripts
)

A group can define the default path for its members. It is taken unless a contained group member defines a path on its own:

.. code-block:: python

scripts = wr.ResourceGroup(name='scripts', path='js')

Same applies for the resource directory. If defined on a resource group, is taken unless a contained member overrides it.

.. code-block:: python

scripts = wr.ResourceGroup(name='scripts', directory='/path/to/scripts')

To control whether an entire group should be included, define an include callback funtion or flag.

.. code-block:: python

def include_group():
    # Compute whether to include resource group here.
    return True

group = wr.ResourceGroup(
    name='group',
    include=include_group,
    ...
)

Deliver resources

Webresource not provides any mechanism to publish the declared resources. It's up to the user to make the resources in the defined directories available to the browser at the defined paths.

But it provides a renderer for the resulting resource HTML tags.

First a ResourceResolver needs to be created knowing about the resources to deliver. members can be an instance or list of resources or resource groups.

The ResourceRenderer then is used to create the markup.

The GracefulResourceRenderer creates the markup, but does not fail if one resource is invalid. It logs an error and places a comment about the failure instead of a HTML-tag.

A complete example:

.. code-block:: python

import webresource as wr

icon = wr.LinkResource(
    name='icon',
    resource='icon.png',
    rel='icon',
    type_='image/png'
)

css = wr.StyleResource(name='css', resource='styles.css')

ext_css = wr.StyleResource(
    name='ext_css',
    url='https://ext.org/styles.css'
)

script = wr.ScriptResource(
    name='script',
    resource='script.js',
    compressed='script.min.js'
)

resources = wr.ResourceGroup(name='resources', path='res')
resources.add(icon)
resources.add(css)
resources.add(ext_css)
resources.add(script)

resolver = wr.ResourceResolver(resources)
renderer = wr.ResourceRenderer(resolver, base_url='https://tld.org')

rendered = renderer.render()

rendered results in:

.. code-block:: html

<link href="https://tld.org/res/icon.png"
      rel="icon" type="image/png" />
<link href="https://tld.org/res/styles.css" media="all"
      rel="stylesheet" type="text/css" />
<link href="https://ext.org/styles.css" media="all"
      rel="stylesheet" type="text/css" />
<script src="https://tld.org/res/script.min.js"></script>

Debugging

To prevent Webresource generating links to the compressed versions of declared resources, development flag of the config singleton needs to be set:

.. code-block:: python

wr.config.development = True

Changelog

1.2 (2022-12-21)

• Accept additional keyword arguments in resources. They get rendered as additional attributes on resource tag. [rnix, aormazabal]

1.1 (2022-07-01)

• Remove relative directory resolving. [rnix]

• Add remove function to ResourceMixin. [rnix]

• Add copy function to ResourceMixin. [rnix]

• Add scripts, styles, and links properties to ResourceGroup. [rnix]

• Introduce parent attribute on ResourceMixin. Gets set in ResourceGroup.add method to provide hierarchy information. [rnix]

• Remove magic path resolving behavior for resources. Path no longer gets overwritten in resolver. It gets now aquired from parent if not set on resource or resource group. [rnix]

• LinkResource and StyleResource have common superclass LinkMixin now. StyleResource no longer derives from LinkResource. This way, link and style resources respective subclasses of it can be differentiated with isinstance. [rnix]

• Remove sizes keyword argument from StyleResource constructor. [rnix]

• ResourceGroup can define a directory for contained resources. [rnix]

• Resource.directory no longer gets set to package path by default but remains None. [rnix]

• Resources can define multiple dependencies. [rnix]

1.0 (2022-03-24)

• Add Tox, Github actions and make it run on Windows. Modernize setup.[py|cfg]. [jensens]

• Added GracefulResourceRenderer. Fixes #1. [jensens]

1.0b8 (2021-09-23)

• Rename hash_ keyword argument of resources to unique.

• Introduce unique_prefix keyword argument on resources.

• Change behavior of unique URL generation. Unique key now gets rendered itermediate between URL path and file name. This way we play nice with caching servers, but this also implies the need of custom URL dispatching/rewriting/traversal when working with unique resource URLs.

1.0b7 (2021-08-16)

• Add auto integrity hash calculation on ScriptResource.

• Add hash_ and hash_algorithm keyword arguments to Resource, ScriptResource, LinkResource and FileResource.

• Add Resource.file_hash property.

• Add Resource.file_data property.

1.0b6 (2021-08-10)

• Raise explicit ResourceError instead of generic ValueError.

1.0b5 (2021-08-09)

• Make Resource.directory a R/W property.

1.0b4 (2021-08-08)

• Change path cascading behavior. Path set on ResourceGroup always takes precedence over its members paths.

• include property of Resource and ResourceGroup can be set from outside.

1.0b3 (2021-08-06)

• Add remaining missing rst files to release.

1.0b2 (2021-08-06)

• Add missing docs/source/overview.rst to release.

1.0b1 (2021-08-06)

• Initial release.