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About

This repo demonstrates that microbundle generates typings matching the directory structure of src. For a single-file package, this introduce relative dependencies in the root .d.ts. This creates a problem when a dependent package tries to resolve those types, as TS does not resolve these relative declarations.

This is specifically targeting the "modern" module build where:

Package Config File Configuration
library package.json type: module
exports.types: ./dist/index.d.ts
tsconfig.json compilerOptions.module: node16
dependent package.json type: module
tsconfig.json compilerOptions.moduleResolution: node16

The library package

Clone repo and run:

npm run build

The the resulting build directory looks like:

dist/
├── foo.d.ts <-------.
├── index.cjs        | 
├── index.cjs.map    | Relative dependency
├── index.d.ts <-----'
├── index.modern.mjs
├── index.modern.mjs.map
├── index.module.mjs
├── index.module.mjs.map
├── index.umd.js
└── index.umd.js.map

The dependent package

Navigate to test-package/. Run npm run build to build the dependent package with tsc version 4.9.4.

Run ./trace-build to build the package and log where the module resolution goes wrong. Output:

======== Module name 'microbundle-typings' was successfully resolved to '~/workspace/microbundle-typings/dist/index.d.ts' with Package ID 'microbundle-typings/dist/index.d.ts@1.0.0'. ========
File '~/workspace/microbundle-typings/dist/package.json' does not exist.
Found 'package.json' at '~/workspace/microbundle-typings/package.json'.
'package.json' does not have a 'typesVersions' field.
======== Resolving module './foo' from '~/workspace/microbundle-typings/dist/index.d.ts'. ========
Explicitly specified module resolution kind: 'Node16'.
Resolving in ESM mode with conditions 'node', 'import', 'types'.
Loading module as file / folder, candidate module location '~/workspace/microbundle-typings/dist/foo', target file type 'TypeScript'.
Directory '~/workspace/microbundle-typings/dist/foo' does not exist, skipping all lookups in it.
Loading module as file / folder, candidate module location '~/workspace/microbundle-typings/dist/foo', target file type 'JavaScript'.
Directory '~/workspace/microbundle-typings/dist/foo' does not exist, skipping all lookups in it.
======== Module name './foo' was not resolved. ========

Note that rejiggering the library's exports doesn't matter, because TS doesn't consider the original module's package.json when looking for relative dependents. Namely, this doesn't change anything:

"exports": {
  "./foo": {
    "types": "./dist/foo.d.ts",
  },
  ".": {
    "types": "./dist/index.d.ts",
    "import": "./dist/index.modern.mjs"
  }
},