Re-exporting default from a dependency in JavaScript produces an invalid declaration file

[esdmr]

Bug Report

🔎 Search Terms

Re-export, default, declaration, module.exports, Identifier expected ts(1003), js, JavaScript.

🕗 Version & Regression Information

• This affects Bundler since version 5.0.
• This affects Node16/NodeNext since version 4.7.
• This affects System since version 3.7.

⏯ Playground Link

Workbench Repro

Switch to the “Debug” tab and look at /index.d.ts. @showEmittedFile did not work.

💻 Code

// @checkJs
// @module: Node16
// @moduleResolution: Node16
// @declaration
// @emitDeclarationOnly

// @filename: index.js
export {default as mod} from 'a';
// @filename: package.json
{"private": true, "type": "module"}
// @filename: node_modules/a/package.json
{"name": "a", "version": "0.0.0"}
// @filename: node_modules/a/index.js
exports.a = 123;
// @filename: node_modules/a/index.d.ts
export const a = 123;

Other cases like this:

• Indirect re-export
  (Only the declaration file that re-exports a dependency will be invalid.)
• index.js: export {default} from 'a';
  (Declaration file will have as default)
• node_modules/a/index.d.ts may be provided separately (e.g., by a @types/ package).
• My comment below

🙁 Actual behavior

Generated index.d.ts is invalid because, instead of re-exporting default as mod, it re-exports "/path/to/node_modules/a/index" as mod. Firstly, there is no export on a/index.js with that identifier. Secondly, TypeScript does not even support “arbitrary module namespace identifier names” (#40594), so the resulting declaration file cannot be subsequently parsed anyway. (Errs Identifier expected. ts(1003).)

🙂 Expected behavior

Generated index.d.ts should simply re-export default as mod, just like the JavaScript file. If node_modules/a is ESM, it should err that there is no export named default.

[typescript-bot]

👋 Hi, I'm the Repro bot. I can help narrow down and track compiler bugs across releases! This comment reflects the current state of the repro in the issue body running against the nightly TypeScript.

---

Issue body code block by @esdmr

👍 Compiled

Historical Information

Version	Reproduction Outputs
4.7.2, 4.8.2, 4.9.3, 5.0.2, 5.1.3	👍 Compiled

[esdmr]

Update on which @module, @moduleResolution, and "type" cause the bug. Columns represent @moduleResolution and rows represent @module. “CJS from ESM” means that node_modules/a/package.json is “CJS” and package.json is “ESM”.

Symbols:

• Empty: Compiler error,
• Dash: Invalid cases (incompatible options or importing ESM from CJS),
• ‘B’: Bug.

version 5.1.6

CJS from CJS	node	node16	nodenext	bundler
AMD				-
CommonJS				-
ES2015				B
ES2020				B
ES2022				B
ESNext				B
Node16	B	B	B	-
NodeNext	B	B	B	-
System	B	B	B	-
UMD				-

CJS from ESM	node	node16	nodenext	bundler
AMD		B	B	-
CommonJS		B	B	-
ES2015		B	B	B
ES2020		B	B	B
ES2022		B	B	B
ESNext		B	B	B
Node16	B	B	B	-
NodeNext	B	B	B	-
System	B	B	B	-
UMD		B	B	-

ESM from CJS	node	node16	nodenext	bundler
AMD		-	-	-
CommonJS		-	-	-
ES2015		-	-	B
ES2020		-	-	B
ES2022		-	-	B
ESNext		-	-	B
Node16	B	-	-	-
NodeNext	B	-	-	-
System	B	-	-	-
UMD		-	-	-

ESM from ESM	node	node16	nodenext	bundler
AMD				-
CommonJS				-
ES2015				B
ES2020				B
ES2022				B
ESNext				B
Node16	B			-
NodeNext	B			-
System	B			-
UMD				-

By comparison, here is the tables for version 4.6.

version 4.6.4

CJS from CJS	node	node16	nodenext	bundler
AMD		-	-	-
CommonJS		-	-	-
ES2015		-	-	-
ES2020		-	-	-
ES2022		-	-	-
ESNext		-	-	-
Node16	-	-	-	-
NodeNext	-	-	-	-
System	B	-	-	-
UMD		-	-	-

CJS from ESM	node	node16	nodenext	bundler
AMD		-	-	-
CommonJS		-	-	-
ES2015		-	-	-
ES2020		-	-	-
ES2022		-	-	-
ESNext		-	-	-
Node16	-	-	-	-
NodeNext	-	-	-	-
System	B	-	-	-
UMD		-	-	-

ESM from CJS	node	node16	nodenext	bundler
AMD		-	-	-
CommonJS		-	-	-
ES2015		-	-	-
ES2020		-	-	-
ES2022		-	-	-
ESNext		-	-	-
Node16	-	-	-	-
NodeNext	-	-	-	-
System	B	-	-	-
UMD		-	-	-

ESM from ESM	node	node16	nodenext	bundler
AMD		-	-	-
CommonJS		-	-	-
ES2015		-	-	-
ES2020		-	-	-
ES2022		-	-	-
ESNext		-	-	-
Node16	-	-	-	-
NodeNext	-	-	-	-
System	B	-	-	-
UMD		-	-	-

(script to run these test cases)

Edit: @allowSyntheticDefaultImports also seems to be related.

version 5.1.6, "esModuleInterop": true or "allowSyntheticDefaultImports": true

CJS from CJS	node	node16	nodenext	bundler
AMD	B	B	B	-
CommonJS	B	B	B	-
ES2015	B	B	B	B
ES2020	B	B	B	B
ES2022	B	B	B	B
ESNext	B	B	B	B
Node16	B	B	B	-
NodeNext	B	B	B	-
System	B	B	B	-
UMD	B	B	B	-

CJS from ESM	node	node16	nodenext	bundler
AMD	B	B	B	-
CommonJS	B	B	B	-
ES2015	B	B	B	B
ES2020	B	B	B	B
ES2022	B	B	B	B
ESNext	B	B	B	B
Node16	B	B	B	-
NodeNext	B	B	B	-
System	B	B	B	-
UMD	B	B	B	-

ESM from CJS	node	node16	nodenext	bundler
AMD	B	-	-	-
CommonJS	B	-	-	-
ES2015	B	-	-	B
ES2020	B	-	-	B
ES2022	B	-	-	B
ESNext	B	-	-	B
Node16	B	-	-	-
NodeNext	B	-	-	-
System	B	-	-	-
UMD	B	-	-	-

ESM from ESM	node	node16	nodenext	bundler
AMD	B			-
CommonJS	B			-
ES2015	B			B
ES2020	B			B
ES2022	B			B
ESNext	B			B
Node16	B			-
NodeNext	B			-
System	B			-
UMD	B			-

version 5.1.6, "allowSyntheticDefaultImports": false

CJS from CJS	node	node16	nodenext	bundler
AMD				-
CommonJS				-
ES2015
ES2020
ES2022
ESNext
Node16				-
NodeNext				-
System				-
UMD				-

CJS from ESM	node	node16	nodenext	bundler
AMD		B	B	-
CommonJS		B	B	-
ES2015		B	B
ES2020		B	B
ES2022		B	B
ESNext		B	B
Node16		B	B	-
NodeNext		B	B	-
System		B	B	-
UMD		B	B	-

ESM from CJS	node	node16	nodenext	bundler
AMD		-	-	-
CommonJS		-	-	-
ES2015		-	-
ES2020		-	-
ES2022		-	-
ESNext		-	-
Node16		-	-	-
NodeNext		-	-	-
System		-	-	-
UMD		-	-	-

ESM from ESM	node	node16	nodenext	bundler
AMD				-
CommonJS				-
ES2015
ES2020
ES2022
ESNext
Node16				-
NodeNext				-
System				-
UMD				-

version 5.1.6, "esModuleInterop": false and "allowSyntheticDefaultImports" unset

CJS from CJS	node	node16	nodenext	bundler
AMD				-
CommonJS				-
ES2015				B
ES2020				B
ES2022				B
ESNext				B
Node16				-
NodeNext				-
System	B	B	B	-
UMD				-

CJS from ESM	node	node16	nodenext	bundler
AMD		B	B	-
CommonJS		B	B	-
ES2015		B	B	B
ES2020		B	B	B
ES2022		B	B	B
ESNext		B	B	B
Node16		B	B	-
NodeNext		B	B	-
System	B	B	B	-
UMD		B	B	-

ESM from CJS	node	node16	nodenext	bundler
AMD		-	-	-
CommonJS		-	-	-
ES2015		-	-	B
ES2020		-	-	B
ES2022		-	-	B
ESNext		-	-	B
Node16		-	-	-
NodeNext		-	-	-
System	B	-	-	-
UMD		-	-	-

ESM from ESM	node	node16	nodenext	bundler
AMD				-
CommonJS				-
ES2015				B
ES2020				B
ES2022				B
ESNext				B
Node16				-
NodeNext				-
System	B			-
UMD				-