/opt/canhelp/node_modules/next/dist/build/webpack/loaders
Edit: /opt/canhelp/node_modules/next/dist/build/webpack/loaders/next-barrel-loader.d.ts (3140B)
/**
* ## Barrel Optimizations
*
* This loader is used to optimize the imports of "barrel" files that have many
* re-exports. Currently, both Node.js and Webpack have to enter all of these
* submodules even if we only need a few of them.
*
* For example, say a file `foo.js` with the following contents:
*
* export { a } from './a'
* export { b } from './b'
* export { c } from './c'
* ...
*
* If the user imports `a` only, this loader will accept the `names` option to
* be `['a']`. Then, it request the "__barrel_transform__" SWC transform to load
* `foo.js` and receive the following output:
*
* export const __next_private_export_map__ = '[["a","./a","a"],["b","./b","b"],["c","./c","c"],...]'
*
* format: '["
", "", ""]'
* e.g.: import { a as b } from './module-a' => '["b", "./module-a", "a"]'
*
* The export map, generated by SWC, is a JSON that represents the exports of
* that module, their original file, and their original name (since you can do
* `export { a as b }`).
*
* Then, this loader can safely remove all the exports that are not needed and
* re-export the ones from `names`:
*
* export { a } from './a'
*
* That's the basic situation and also the happy path.
*
*
*
* ## Wildcard Exports
*
* For wildcard exports (e.g. `export * from './a'`), it becomes a bit more complicated.
* Say `foo.js` with the following contents:
*
* export * from './a'
* export * from './b'
* export * from './c'
* ...
*
* If the user imports `bar` from it, SWC can never know which files are going to be
* exporting `bar`. So, we have to keep all the wildcard exports and do the same
* process recursively. This loader will return the following output:
*
* export * from '__barrel_optimize__?names=bar&wildcard!=!./a'
* export * from '__barrel_optimize__?names=bar&wildcard!=!./b'
* export * from '__barrel_optimize__?names=bar&wildcard!=!./c'
* ...
*
* The "!=!" tells Webpack to use the same loader to process './a', './b', and './c'.
* After the recursive process, the "inner loaders" will either return an empty string
* or:
*
* export * from './target'
*
* Where `target` is the file that exports `bar`.
*
*
*
* ## Non-Barrel Files
*
* If the file is not a barrel, we can't apply any optimizations. That's because
* we can't easily remove things from the file. For example, say `foo.js` with:
*
* const v = 1
* export function b () {
* return v
* }
*
* If the user imports `b` only, we can't remove the `const v = 1` even though
* the file is side-effect free. In these caes, this loader will simply re-export
* `foo.js`:
*
* export * from './foo'
*
* Besides these cases, this loader also carefully handles the module cache so
* SWC won't analyze the same file twice, and no instance of the same file will
* be accidentally created as different instances.
*/
import type webpack from 'webpack';
declare const NextBarrelLoader: (this: webpack.LoaderContext<{
names: string[];
swcCacheDir: string;
}>) => Promise;
export default NextBarrelLoader;