New --emitExtension and --noImplicitExtensionName compiler options by Jack-Works · Pull Request #35148 · microsoft/TypeScript (original) (raw)

Related: denoland/deno#8529, #27957, #35749

fixes #30076, fixes #18442, fixes #16577, fixes #33306

See also: Node.js new ESModule support: https://medium.com/@nodejs/announcing-core-node-js-support-for-ecmascript-modules-c5d6dc29b663

Summary

Improve support for deno and browser style import. Note: This pr doesn't include URI style import resolution (https://deno.land/... or std:kv-storage...), about URI style import, see #35749

New --noImplicitExtensionName compiler options.

With this option on, the following code becomes invalid.

This new options will enforce developer to write valid import path on deno (noImplicitExtensionName + emitExtension=.ts) and ES Module for browser (noImplicitExtensionName + emitExtension=.js (default value)).

New --emitExtension compiler options.

This flag allows tsc to emit .mjs, .es.js, .es, .ts or any extension user specifies.

tsconfig.json

{ compilerOptions: { emitExtension: ".mjs", noImplicitExtensionName: true } }

Source files:

Emitted files:

Discussions

According to #35163 (comment) maybe --noImplicitExtensionName should be default to true when the target module system is ESModule

Details

Due to the ts meeting note for this pr (#35589 )
I decided to rewrite ts pr to follow the ts design principle.

• Resolve TS file by --emitExtension
• Type error for import with no extension name
• Emit file as ext of emitExtension
• Allow import .ts and .tsx file when emitExtension === .ts or .tsx
• If the extension name !== emitExtension, emit a compile error

Resolve TS file by --emitExtension

Resolve type of import './x.mjs' to the file x.ts.
Will NOT rewrite the emitted file path.