Design Meeting Notes, 9/17/2024

[DanielRosenwasser]

Extension Rewriting

#59767

• We've discussed what we need to do with async imports.
  • One possibility: you do the transform yourself.
  • Another: we provide a runtime shim - possibly overridable.
• Also: we have the same situation for require calls in JS input files.
  • It is currently not as common, but possible, for us to transform JavaScript input files.
  • Those files can still refer to .ts files - do we want rewriting for those?
• Does the experimental mode in Node support require?
  • Pretty sure it does?
• There's require with a plain string and an arbitrary expression.
  • Why do we care about this difference?
  • require can be passed into arbitrary places.
    • Makes us inclined to say no shimming.
• We could error on require of an arbitrary expression in this mode.
  • People can always alias require or // @ts-ignore.
• Extension rewriting was always weird - but if we're gonna do it, maybe we should do it in a maximalist way?
  • Feels like if semantics diverges between runtime and emit, that's a problem.
• Could just say only require on static imports.
• Can you just create arbitrary requires?
  • Yes, there's createRequire - could maybe monkey-patch this?
  • Also require.call(...)
• Could add an import attribute to turn off rewriting for import().
• Moved from "don't shim anything" to "shim everything".
• Between import attributes and (require)(...) these are reasonable opt-outs.
• Also open to just a global flag...
• Or a third state for the flag.
  • "none", "staticImportsOnly", "bestEffort"?