`@rollup/plugin-typescript` should error on TypeScript import of missing `.json` file (bundled with a different name by `@rollup/plugin-json`)

[andersk]

• Rollup Plugin Name: @rollup/plugin-typescript
• Rollup Plugin Version: 12.3.0

Feature Use Case

Careless use of @rollup/plugin-typescript and @rollup/plugin-json together results in broken TypeScript declarations, in a way that’s difficult to detect until after the package is published. A real example of this regression happening twice in the same package:

• [3.0.0 regression] error TS7016: Could not find a declaration file for module './adjacencyGraphs.json' zxcvbn-ts/zxcvbn#200
• [4.1.0 regression] error TS2307: Cannot find module './adjacencyGraphs.json' or its corresponding type declarations. zxcvbn-ts/zxcvbn#319

Here’s a minimal reproducible example:

package.json, tsconfig.json, src/data.json

package.json

{
  "name": "rollup-typescript-json-test",
  "version": "0.0.0",
  "private": true,
  "type": "module",
  "main": "dist/index.js",
  "types": "dist/index.d.ts",
  "devDependencies": {
    "@rollup/plugin-json": "^6.1.0",
    "@rollup/plugin-typescript": "^12.3.0",
    "rollup": "^4.61.1",
    "typescript": "^6.0.3"
  }
}

tsconfig.json

{
  "compilerOptions": {
    "declaration": true,
    "module": "nodenext",
    "noEmit": true,
    "outDir": "dist",
    "rootDir": "src"
  }
}

src/data.json

[0, 1, 2]

rollup.config.js

import json from "@rollup/plugin-json";
import typescript from "@rollup/plugin-typescript";

export default {
  input: "src/index.ts",
  plugins: [json(), typescript({ rootDir: "src" })],
  output: { dir: "dist", preserveModules: true },
};

src/index.ts

import data from "./data.json" with { type: "json" };

export { data };

It passes tsc and seemingly builds cleanly with rollup -c, but the resulting type declarations are broken in a way that’s difficult to notice until after publication.

$ npm i
$ npx tsc
$ npx rollup -c

src/index.ts → dist...
created dist in 315ms
$ npx tsc --ignoreConfig --noEmit --module nodenext dist/index.d.ts
dist/index.d.ts:1:18 - error TS2307: Cannot find module './data.json' or its corresponding type declarations.

1 import data from "./data.json";
                   ~~~~~~~~~~~~~


Found 1 error in dist/index.d.ts:1

$ npx tsc --ignoreConfig --noEmit dist/index.d.ts
dist/index.d.ts:1:18 - error TS7016: Could not find a declaration file for module './data.json'. '/home/anders/zulip/test/plugin-typescript-dts-json-repro/dist/data.json.js' implicitly has an 'any' type.

1 import data from "./data.json";
                   ~~~~~~~~~~~~~


Found 1 error in dist/index.d.ts:1

dist/data.json.js, dist/index.d.ts, dist/index.js

dist/data.json.js

var data = [
	0,
	1,
	2
];

export { data as default };

dist/index.d.ts

import data from "./data.json";
export { data };

dist/index.js

export { default as data } from './data.json.js';

The emitted declarations point to a nonexistent dist/data.json. The problem is that @rollup/plugin-json has emitted dist/data.json.js rather than dist/data.json, but TypeScript has no way to know this and couldn’t use dist/data.json.js even if it knew.

One way to discover this problem is using @arethetypeswrong/cli:

$ npx @arethetypeswrong/cli --pack .

rollup-typescript-json-test v0.0.0

Build tools:
- typescript@^6.0.3
- rollup@^4.61.1
- @rollup/plugin-typescript@^12.3.0

⚠️ A require call resolved to an ESM JavaScript file, which is an error in Node and some bundlers. CommonJS consumers will need to use a dynamic import. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/CJSResolvesToESM.md

🥴 Import found in a type declaration file failed to resolve. Either this indicates that runtime resolution errors will occur, or (more likely) the types misrepresent the contents of the JavaScript files. Use -f json to see the imports that failed to resolve. https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/InternalResolutionError.md


┌───────────────────┬───────────────────────────────┐
│                   │ "rollup-typescript-json-test" │
├───────────────────┼───────────────────────────────┤
│ node10            │ 🟢                            │
├───────────────────┼───────────────────────────────┤
│ node16 (from CJS) │ ⚠️ ESM (dynamic import only)  │
│                   │ 🥴 Internal resolution error  │
├───────────────────┼───────────────────────────────┤
│ node16 (from ESM) │ 🥴 Internal resolution error  │
├───────────────────┼───────────────────────────────┤
│ bundler           │ 🟢                            │
└───────────────────┴───────────────────────────────┘

But @arethetypeswrong/cli isn’t used nearly as widely as it should be, so it would be better if @rollup/plugin-typescript could somehow detect this problem before it happens.

Feature Proposal

@rollup/plugin-typescript could try to resolve relative imports and re-exports within the emitted declarations against the set of emitted files, and complain if any are missing.