research on conditional/when after and before

[caridy]

Part of the alignments with ES modules will require some adjustments in our current conditional loading strategy. As today, YUI Core only uses after and instead as values for when property when defining a conditional module, it doesn't use before although we have tests for them, and there might be some people using it.

The problem is that in ES there is not after and before, only instead, since each module is suppose to export something, and you should not mix the export with more things that happen after or before.

After looking at the metas today, it seems like the use of after is hacky, and could be solved by implementing instead, and having a more granular approach for the things that are common for multiple modules.

Here is the current meta using after:

    "yql-jsonp": {
        "condition": {
            "name": "yql-jsonp",
            "test": function (Y) {
                  /* Only load the JSONP module when not in nodejs or winjs
                  TODO Make the winjs module a CORS module
                  */
                  return (!Y.UA.nodejs && !Y.UA.winjs);
            },
            "trigger": "yql",
            "when": "after"
        },
        "requires": [
            "jsonp",
            "jsonp-url"
        ]
    },
    "yql-nodejs": {
        "condition": {
            "name": "yql-nodejs",
            "trigger": "yql",
            "ua": "nodejs",
            "when": "after"
        }
    },
    "yql-winjs": {
        "condition": {
            "name": "yql-winjs",
            "trigger": "yql",
            "ua": "winjs",
            "when": "after"
        }
    }

Ideally, we could have a yql-base that implements the shared pieces between all these 3 modules, and then having yql, yql-winjs and yql-nodejs to depend on it, then having yql-winjs as a replacement for yql when in winjs, and the same for the nodejs version. That's a more elegant solution, and we could finally kill the when property, implementing the instead path for all conditionals.

In the case of the yql-jsonp, this really qualifies as an optionalRequires, specially if it depends on yql-base. Where yql is just a simple shim around the yql-base implementation.

Here is the proposed meta:

    "yql-base": {}
    "yql": {
        "requires": ["yql-base"],
        "optionalRequires": ["yql-jsonp"]
    },
    "yql-jsonp": {
        "test": function (Y) {
                  /* Only load the JSONP module when not in nodejs or winjs
                  TODO Make the winjs module a CORS module
                  */
                  return (!Y.UA.nodejs && !Y.UA.winjs);
        },
        "requires": [
            "jsonp",
            "jsonp-url"
        ]
    },
    "yql-nodejs": {
        "condition": {
            "name": "yql-nodejs",
            "trigger": "yql",
            "ua": "nodejs"
        }
    },
    "yql-winjs": {
        "condition": {
            "name": "yql-winjs",
            "trigger": "yql",
            "ua": "winjs"
        }
    }

/cc @juandopazo

[juandopazo]

We should probably have this conversation in yui-contrib.

[caridy]

sure thing. /cc @triptych

[triptych]

Yeah, I'd say just kick off a thread in yui-contrib to point to this issue, so you can capture the discussion here.
This is similar to how Satyen worked on the YUI performance work he did.

[caridy]

Discussion is here: https://groups.google.com/forum/#!topic/yui-contrib/MozIbGBQm2w

[caridy]

Related to issue #1661 and PR #1704