prefer commonjs externals even if "module" condition is used in package.json
## Bug
- [ ] Related issues linked using `fixes #number`
- [x] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`
add `experimental.esmExternals: boolean | 'loose'` config option
remove `output.environment` configuration in favor of `target`
| | `esmExternals: false` (default) | `esmExternals: 'loose'` | `esmExternals: true` |
| ------------------------ | ------------------------------- | ----------------------- | -------------------- |
| import cjs package | `require()` | `require()` | `require()` |
| require cjs package | `require()` | `require()` | `require()` |
| import mixed package | `require()` *** | `import()` | `import()` |
| require mixed package | `require()` | `require()` | `require()` |
| import pure esm package | `import()` | `import()` | `import()` |
| require pure esm package | Error ** | `import()` * | Error ** |
| import pure cjs package | `require()` | `require()` | Resolving error |
| require pure cjs package | `require()` | `require()` | `require()` |
cjs package: Offers only CJS implementation (may not even have an `exports` field)
mixed package: Offers CJS and ESM implementation via `exports` field
pure esm package: Only offers an ESM implementation (may not even have an `exports` field)
pure cjs package: CommonJs package that prevents importing via `exports` field when `import` is used.
`*` This case will behave a bit unexpected for now, since `require` will return a Promise. So that need to be awaited. This will be fixed once the whole next.js bundle is ESM. It didn't work at all before this PR.
`**` This is a new Error when trying to require an esm package.
`***` For mixed packages we prefer the CommonJS variant to avoid a breaking change.
## Feature
- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [x] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [x] Errors have helpful link attached, see `contributing.md`
## Documentation / Examples
- [ ] Make sure the linting passes
