Module Types Extra

[guybedford]

This implements the fallback approach as discussed in #2005 (comment), while abstracting all module types into their own extra.

This replaces the Web Assembly feature with a single module types extra, removing .json support in the s.js loader too so that it would need this extra for JSON support.

This gets the s.js loader footprint back down to 1.5KiB.

The hardest part was testing it, which required a custom server harness for the tests. Nice to have this finally though :)

[guybedford]

I've updated this PR to also bring all the different module types into a dedicated module-types extra that is not included in s.js by default. This allows s.js to get Web Assembly support too now!

[joeldenning]

This looks good to me. I think it's a little weird that we support js fallback for wasm and html, but not for json or css. But I like that this is pulled out into an extra.

[joeldenning]

👏 I think that this is better as an extra than baked into s.js and script-load. And am also glad that the module-types extra is included by default into system.js

[guybedford]

Thanks for the review, merging to prep for the composition PR, then hopefully we're getting there on v6.

I think it's a little weird that we support js fallback for wasm and html, but not for json or css

We support the fallback of application/javascript for all the fetch types.

[joeldenning]

We support the fallback of application/javascript for all the fetch types.

Ah I see that now -- misread the code earlier. 👍 this looks good.