Unify js library configuration model
------------------------------------
Key: SHINDIG-22
URL: https://issues.apache.org/jira/browse/SHINDIG-22
Project: Shindig
Issue Type: Improvement
Reporter: Kevin Brown
Assignee: Kevin Brown
Introduce a unified configuration model for all JsLibrary features to avoid
inline scripts being used for configuration. This improves type=url support,
reduces errors, and minimizes the number of changes required by integrators who
need to roll up their systems.
My proposal is to add a config namespace to gadgets.*, which is not part of the
gadgets spec, but can be safely depended on by anyone writing features for the
shindig platform (using the feature.xml mechanism). A rough API spec:
/**
* Registers a configurable component and its configuration parameters.
*
* @param {string} component The name of the component to register. Should be
the same as the fully qualified name of the <Require> feature or the fully
qualified javascript object reference (e.g. gadgets.io).
* @param {object} config Mapping of option name to validation function that
takes the form function(data) {return valid(data) ? true : false;}
* @param {function} opt_callbackA function to be invoked when a configuration
is registered. If passed, this function will be invoked immediately after a
call to init has been made. Do not assume that dependent libraries have been
configured until after init is complete. If you rely on this, it is better to
defer calling dependent libraries until you can be sure that configuration is
complete. Takes the form function(errors, extra), where errors will be an array
of parameters that failed to validate, and extra will be any parameters that
were specified that you did not explicitly register up front.
*/
gadgets.config.register = function(component, config, opt_callback);
/**
* Used when a configuration needs to be fetched for a component that did not
register a callback. Useful when inspecting the config parameters of another
component.
*
* @param {string} component @see gadgets.config.register
* @return {object} The component's config parameters
* @throws {Error} When requesting a component that was not registered.
*/
gadgets.config.get = function(component);
/**
* @param {object} config. All feature configuration, in the form:
* <code>
* {"component": {property: "value"}};
* </code>
**/
gadgets.config.init = function(config);
We should also provide a list of common validation routines (regular expression
based, enumeration based, etc.). For example:
gadgets.config.enumValidator = function(list) {
return function(data) {
for (var i = 0, test; test = list[i]; ++i) {
if (data === list[i]) {
return true;
}
}
return false;
}
}
gadgets.config.regexValidator = function(re) {
return function(data) {
return re.test(data);
}
}
To make all of this work correctly:
- gadgets.config *must* be the first library included in core (easily handled
by JsFeatureLoader, which guarantees the order of includes)
- gadgets.config.init *must* be called after all features have been fully
loaded and have registered their configuration
- gadgets.config.init *must* be called before any feature-dependent code is
called, such as gadget rendering code.
- features that use gadgets.config *must not* execute any code via up front
initialization that depends on config being registered, and should instead
provide init callbacks and / or provide lazy configuration retrieval mechanisms.
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