Scala.js: Implement JS exports. #10164
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I added a commit that adds neg tests and makes them pass. It should be squashed eventually, so if you haven't started reviewing, it's better to review the PR diff than the commits separately. |
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As a consequence, this fixes scala#9881.
Compared to the implementation in Scala 2, there is one significant difference. In Scala 2, top-level exports and static exports info are computed by `PrepJSInterop` and stored in an out-of-band mutable Map until the back-end. In this implementation, `PrepJSInterop` only performs checks for compile error messages, and the required data are recomputed by the back-end from the annotations. Since dotc does not (currently?) constant-fold expressions within annotations, `PrepJSInterop` specifically constant-folds the arguments of `@JSExportTopLevel` and `@JSExportStatic`, so that the literal values can be recovered by the back-end.
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Rebased, squashed, and added |
| } else /*if (jsInterop.topLevelExportsOf(sym).nonEmpty) { | ||
| val f = js.SelectStatic(encodeClassName(sym.owner), | ||
| encodeFieldSym(sym))(jstpe.AnyType) | ||
| } else if (sym.hasAnnotation(jsdefn.JSExportTopLevelAnnot)) { |
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Do you recall why we didn't simply do this in Scala 2?
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I don't know. It's probably historical, following a long chain of changes. @JSExportTopLevel inherited from @JSExport on classes and objects, in which the name could be implicit; which might explain it. git blame suggests scala-js/scala-js@273e9b8 as the moment at which we introduced those out-of-the-band mutable maps, but at the time @JSExportTopLevel did not exist yet.
We could try to get rid of it in Scala 2.
Compared to the implementation in Scala 2, there is one significant difference. In Scala 2, top-level exports and static exports info are computed by
PrepJSInteropand stored in an out-of-band mutable Map until the back-end. In this implementation,PrepJSInteroponly performs checks for compile error messages, and the required data are recomputed by the back-end from the annotations.Since dotc does not (currently?) constant-fold expressions within annotations,
PrepJSInteropspecifically constant-folds the arguments of@JSExportTopLeveland@JSExportStatic, so that the literal values can be recovered by the back-end.