Support circular dependencies and export let with experimentalImportSupport #1429
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Summary:
Currently, `experimentalImportSupport` transforms named imports such that they're accessed immediately at the top level, eg:
```js
import {foo} from 'bar';
export function getFoo() {
return foo;
}
```
Becomes
```js
Object.defineProperty(exports, '__esModule', {
value: true
});
var foo = require('bar').foo;
function getFoo() {
return foo;
}
exports.getFoo = getFoo;
```
This immediate, top-level assignment of `require('bar').foo` to `foo` problematic for two reasons:
1. In the case of circular dependencies, the module at `'bar'` may not have been fully initialised, so that `foo` might be undefined at this point.
2. In the case where `bar` defines `export let foo = 'something mutable'`, a reassigment of `foo` within `'bar'` at runtime will not be reflected by the importing module.
Differential Revision: D68394514
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This pull request was exported from Phabricator. Differential Revision: D68394514 |
Summary:
NOTE: This is an opt-in extension to `experimentalImportSupport`, this diff is a no-op by default.
Currently, `experimentalImportSupport` transforms named imports such that they're accessed immediately at the top level, eg:
```js
import {foo} from 'bar';
export function getFoo() {
return foo;
}
```
Becomes
```js
Object.defineProperty(exports, '__esModule', {
value: true
});
var foo = require('bar').foo;
function getFoo() {
return foo;
}
exports.getFoo = getFoo;
```
This immediate, top-level assignment of `require('bar').foo` to `foo` problematic for two reasons:
1. In the case of circular dependencies, the module at `'bar'` may not have been fully initialised, so that `foo` might be undefined at this point.
2. In the case where `bar` defines `export let foo = 'something mutable'`, a reassignment of `foo` within `'bar'` at runtime will not be reflected by the importing module.
This aims to fix 1 and get closer to a fix for 2. The new output would be:
```js
Object.defineProperty(exports, '__esModule', {
value: true
});
var _bar = require('bar');
function getFoo() {
return _bar.foo;
}
exports.getFoo = getFoo;
```
By lazily accessing values
Differential Revision: D68394514
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This pull request was exported from Phabricator. Differential Revision: D68394514 |
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Summary:
Currently,
experimentalImportSupporttransforms named imports such that they're accessed immediately at the top level, eg:Becomes
This immediate, top-level assignment of
require('bar').footofoois problematic for two reasons:'bar'may not have been fully initialised, so thatfoomight be undefined at this point.bardefinesexport let foo = 'something mutable', a reassigment offoowithin'bar'at runtime will not be reflected by the importing module.Differential Revision: D68394514