Migrate to SystemJS module format from AMD for bundles #3559
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kitsonk
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Moves to using a minimal System loader for bundles generated by Deno. TypeScript in 3.8 will be able to output TLA for modules, and the loader is written to take advantage of that as soon as we update Deno to TS 3.8. System also allows us to support `import.meta` and provide more ESM aligned assignment of exports, as well as there is better handling of circular imports. The loader is also very terse versus to try to save overhead. Also, fixed an issue where abstract classes were not being rexported. Fixes denoland#2553 Fixes denoland#3559 Fixes denoland#3751 Fixes denoland#3825 Refs denoland#3301
kitsonk
added a commit
to kitsonk/deno
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Feb 11, 2020
Moves to using a minimal System loader for bundles generated by Deno. TypeScript in 3.8 will be able to output TLA for modules, and the loader is written to take advantage of that as soon as we update Deno to TS 3.8. System also allows us to support `import.meta` and provide more ESM aligned assignment of exports, as well as there is better handling of circular imports. The loader is also very terse versus to try to save overhead. Also, fixed an issue where abstract classes were not being rexported. Fixes denoland#2553 Fixes denoland#3559 Fixes denoland#3751 Fixes denoland#3825 Refs denoland#3301
ry
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Feb 12, 2020
Moves to using a minimal System loader for bundles generated by Deno. TypeScript in 3.8 will be able to output TLA for modules, and the loader is written to take advantage of that as soon as we update Deno to TS 3.8. System also allows us to support `import.meta` and provide more ESM aligned assignment of exports, as well as there is better handling of circular imports. The loader is also very terse versus to try to save overhead. Also, fixed an issue where abstract classes were not being re-exported. Fixes #2553 Fixes #3559 Fixes #3751 Fixes #3825 Refs #3301
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As pointed out in #2475 comment supporting top level await in bundles is going to be problematic.
In AMD, the define factory function needs to return immediately according to the standard. There are specific issues in the specification relating to attempting to provide an asynchronous define function, and there has been strong feedback to not allow this. While we could of course implement a loader that supported an asynchronous return from the define factory, it would require us to convince the TypeScript team to emit AMD modules that were not compliant to the spec, which they would rightfully push back on.
So the only other "quick" solution is to migrate to SystemJS format for bundles, as the module definition supports asynchronous returns.
Other non-quick solutions is to implement some sort specialised bundle format, which is complicated and may cause more challenges as we hit edge cases in the way exports are handled, and modules formed. I still think it would be a lot better to rely upon something that is done by TypeScript and we handle.
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