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Zend Framework: Zend_Dojo Automated Build Layers Component Proposal

Proposed Component Name Zend_Dojo Automated Build Layers
Developer Notes http://framework.zend.com/wiki/display/ZFDEV/Zend_Dojo Automated Build Layers
Proposers Matthew Weier O'Phinney
Zend Liaison Ralph Schindler
Revision 0.1 - 13 January 2009: Initial Draft.
0.2 - 25 January 2009: More comprehensive overview; modified requirements; referenced laboratory prototype (wiki revision: 6)

Table of Contents

1. Overview

Dojo is a highly modular Javascript framework with a structure that largely mirrors the 1-class-1-file structure of Zend Framework and PEAR. During development, this is an incredibly powerful paradigm as it provides the flexibility to add new functionality as needed. However, once in production, it can be a liability: each class loaded through dojo.require requires at least one, and in many cases dozens, of additional requests to the server to load dependencies. Fortunately, Dojo has a solution for this via custom builds.

Creating custom builds is relatively trivial. However, at this time, it requires the developer to examine each page, aggregate the dojo.require and other statements, create a layer file, and create the build profile.

Zend_Dojo provides a common point of aggregation for all these areas, and could be introspected to build a custom layer file and related build profile, which would leave creating the actual build as the only step necessary by the developer. This proposal aims to address this idea.

How Dojo custom layers work

Rather than generate a large number of dojo.require statements for every page, a
common solution in Dojo is to create what is known as a layer script. A layer
script typically is namespace, and contains simply a number of dojo.require
statements:

These scripts may also contain JavaScript to run on every request, such as dojo.addOnLoad events, definition of dojo.data stores, etc. Such an approach might look like this:

Within your view markup, then you would simply dojo.require this single layer script:

This approach has the benefit of making it easier to maintain your view scripts between environments, and prevents the necessity of constantly updating application code.

Dojo itself leverages this paradigm in its build system. The build system can use a layer script as a dependency, and compile all JavaScript into a single file, pulling in all dependencies recursively. Additionally, it can strip out comments, whitespace, and perform optimizations on the code.

Build profiles are simply JavaScript, and define the various build options, layers, and dependencies. An example for the above might look like the following:

Several things to note about it. First, note that the layer has a dependency on
itself. This allows you to reference the same module in your dojo.require both
before and after the build. Second, note that even though dojo.parser was
referenced in a dojo.require statement, there is no "dojo" prefix defined; the
dojo directory will always be included in the build.

You then pass this profile to the build script, typically located in
util/buildscripts/ of the dojo distribution. You need to provide the location of
the profile script, and a release directory. As an example:

The benefits to using custom builds are tremendous:

  • Decreased load times for end users. Without a build, each dojo.require statement will produce an XmlHttpRequest round trip with the server, leading to often dozens of calls; with a build script, these are practically eliminated. Additionally, due to the build stripping out white space and comments and doing code optimizations, the final file size is a fraction of the cumulative file size.
  • Faster JavaScript responses. The build process performs a number of code optimizations, resulting in snappier response times for JS operations.
  • Optionally, you can also request build operations on CSS associated with your custom Dojo namespace. This will evaluate all @import statements and pull the CSS from those files into a single file, and strip comments and whitespace. The result is a single, smaller CSS file – again, leading to decreased load times for end users.

But where does Zend Framework fit into this?

Proposed Zend Framework integration

The dojo() view helper aggregates all the information needed by a build layer: the various dojo.require statements, dojo.addOnLoad events (if desired), and Dojo-related initialization javascript (if desired).

We propose a class that can take the metadata contained in the dojo() view helper in order to generate both a layer script and a build profile. This will simplify the deployment story for developers using Zend Framework and Dojo.

This class will also allow aggregating the results of visiting several pages with differing Dojo requirements, allowing developers to create comprehensive build layers for their site.

2. References

3. Component Requirements, Constraints, and Acceptance Criteria

  • This component MUST provide the ability to generate Dojo custom layer files.
    • The component MUST allow specifying the layer name
    • The component MUST allow specifying whether or not to include dojo.addOnLoad events and/or Dojo-related JavaScript aggregated in the helper
  • The component MUST allow creating the build profile
    • The generated layer file MUST allow specifying the layer script path (relative to dojo.js)
    • The generated layer file MUST determine the dependent namespaces from the dojo.require statements
    • The component MUST allow specifying arbitrary build options
    • The component MUST provide default recommended build options
  • This component SHOULD allow parsing an existing layer file into tokens
    • The component SHOULD check to see if new dojo.require statements and/or javascript have been registered; if so, it MUST create a composite file

4. Dependencies on Other Framework Components

  • Zend_Dojo_View_Helper_Dojo
  • Zend_Dojo_View_Helper_Dojo_Container

5. Theory of Operation

When configuring the dojo() view helper, you will be able to optionally specify an automated build layer. When doing so, you will be able to specify a variety of options:

  • The layer namespace (e.g., "custom", "bug", "contact")
  • The filesystem path to the layer (e.g., APPLICATION_PATH . '/../public/js/custom'); by default, this will be auto-discovered based on the path to dojo.js and the public directory (assumed to be APPLICATION_PATH . '/../public').
  • The path to the layer, relative to dojo.js (e.g., '../custom'); by default, this will be assumed to be the '../$layerNamespace'.
  • The path to the build profile (e.g., APPLICATION_PATH . "/../misc/$layerNamespace.profile.js"); by default, this will be auto-discovered based on the path to dojo.js, and will be in ../util/buildscripts/profiles/$layerNamespace.profile.js.
  • Flag indicating whether only dojo.require statements should be part of the layer, or if all javascript captured by the dojo() view helper should be included. By default, only the dojo.require statements will be included.
  • Flag indicating whether or not the helper should update an existing layer file.

Once you have, anytime a page is hit where the dojo() view helper is rendered, the layer file will either be created or updated, and a corresponding build profile will as well. It is then up to the developer to either manually generate the build from the build profile, or create an automated task for doing so.

6. Milestones / Tasks

  • Milestone 1: Creation of proposal
  • Milestone 2: Working prototype created targetting all MUST and WILL requirements, including unit tests
  • Milestone 3: Updated prototype supporting all SHOULD and COULD requirements, including unit tests
  • Milestone 4: Full documentation of new functionality
  • Milestone 5: Review for inclusion in trunk

7. Class Index

  • Zend_Dojo_View_Helper_Dojo_Layer
  • Zend_Dojo_View_Helper_Dojo_BuildProfile
  • Zend_Dojo_View_Helper_Dojo_Container (updates)

8. Use Cases

UC-01

Fully automated build layer

The example below creates a fully automated build layer in ../custom/main.js (relative to dojo.js). As the developer browses to pages that utilize different Dojo functionality, it will be updated. Additionally, it will create a build profile in ../util/buildscripts/profiles/custom.profile.js.

UC-02

Aggregate javascript in the build layer

The example below builds on UC-01, and sets a flag telling the dojo() view helper to aggregate javascript to the build layer.

UC-03

Only create the build layer file once

The next example builds on the previous, and sets a flag indicating that the build layer file should only be created once, and never updated.

UC-04

Manually specify where to place the build layer file

UC-05

Manually specify where to put the build profile file

9. Class Skeletons

TBD

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