ComfyChloe opened a new issue, #21778:
URL: https://github.com/apache/echarts/issues/21778
## Summary
echarts declares `"types": "index.d.ts"` in its package manifest, but
`index.d.ts` is authored in CommonJS style and ends with `export = echarts`.
TypeScript rejects that when the consuming project targets ECMAScript modules,
so any modern ESM project with `skipLibCheck: false` fails to typecheck.
## Affected file
```ts
// node_modules/echarts/index.d.ts (lines 21-23)
import * as echarts from './types/dist/echarts';
// Export for UMD module.
export as namespace echarts;
export = echarts; // <-- TS1203 under `module: ESNext`
```
## Package manifest (5.6.0)
```json
{
"main": "dist/echarts.js",
"module": "index.js",
"types": "index.d.ts",
"exports": {
".": {
"types": "./index.d.ts",
"import": "./index.js",
"require": "./dist/echarts.js"
}
}
}
```
Both the legacy `types` field and the `exports["."].types` condition resolve
to the CommonJS-authored `index.d.ts`. The ESM-friendly declarations already
exist at `./types/dist/echarts.d.ts` and are exported (e.g.
`./types/dist/echarts`), but the default entrypoint does not point at them.
## Reproduction
```jsonc
// tsconfig.json
{
"compilerOptions": {
"target": "ES2022",
"module": "ESNext",
"moduleResolution": "bundler",
"lib": ["ES2023", "DOM"],
"strict": true,
"skipLibCheck": false,
"noEmit": true
}
}
```
```ts
import type { EChartsOption } from 'echarts';
export const o: EChartsOption = {};
```
```
error TS1203: Export assignment cannot be used when targeting ECMAScript
modules.
Consider using 'export default' or another module format instead.
at node_modules/echarts/index.d.ts:23:1
```
This error appears regardless of `exactOptionalPropertyTypes`; it is purely
the `module: ESNext` + `export =` combination.
## Relation to previously closed issues
ESM compatibility has been reported and closed before — #20554
("Compatibility with ESM") and #21250 ("Cannot use ESM imports in modern
TypeScript project"). Both were closed, yet the default `types` entry still
resolves to a CommonJS declaration file in 5.6.0, so this looks like a
regression rather than a new problem.
## Suggested fix
Point the type entrypoints at the ESM declaration file, e.g. ship an
`index.d.mts` (or make `index.d.ts` ESM-authored) and have `exports["."]`
select it:
```json
{
"exports": {
".": {
"import": { "types": "./index.d.mts", "default": "./index.js" },
"require": { "types": "./index.d.ts", "default": "./dist/echarts.js" }
}
}
}
```
## Environment
- echarts 5.6.0
- TypeScript 5.9.3
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