feat: emitFile option

README.md

@@ -261,6 +261,7 @@ module.exports = {
 |              Name               |         Type         |              Default               | Description                                                                       |
 | :-----------------------------: | :------------------: | :--------------------------------: | :-------------------------------------------------------------------------------- |
 | **[`publicPath`](#publicPath)** | `{String\|Function}` | `webpackOptions.output.publicPath` | Specifies a custom public path for the external resources like images, files, etc |
+|       **[`emit`](#emit)**       |     `{Boolean}`      |               `true`               | If false, the plugin will extract the CSS but **will not** emit the file          |
 |   **[`esModule`](#esModule)**   |     `{Boolean}`      |               `true`               | Use ES modules syntax                                                             |
 |    **[`modules`](#modules)**    |      `{Object}`      |            `undefined`             | Configuration CSS Modules                                                         |
 
@@ -344,6 +345,14 @@ module.exports = {
 };
 ```
 
+#### `emit`
+
+Type: `Boolean`
+Default: `true`
+
+If true, emits a file (writes a file to the filesystem). If false, the plugin will extract the CSS but **will not** emit the file.
+It is often useful to disable this option for server-side packages.
+
 #### `esModule`
 
 Type: `Boolean`

src/loader-options.json

@@ -12,6 +12,9 @@
         }
       ]
     },
+    "emit": {
+      "type": "boolean"
+    },
     "esModule": {
       "type": "boolean"
     },

src/loader.js

@@ -189,21 +189,16 @@ export function pitch(request) {
   childCompiler.runAsChild((error, entries, compilation) => {
     const assets = Object.create(null);
     const assetsInfo = new Map();
+    const emit = typeof options.emit !== 'undefined' ? options.emit : true;
 
-    for (const asset of compilation.getAssets()) {
-      assets[asset.name] = asset.source;
-      assetsInfo.set(asset.name, asset.info);
+    if (emit) {
+      for (const asset of compilation.getAssets()) {
+        assets[asset.name] = asset.source;
+        assetsInfo.set(asset.name, asset.info);
+      }
     }
 
     const addDependencies = (dependencies) => {
-      if (!Array.isArray(dependencies) && dependencies != null) {
-        throw new Error(
-          `Exported value was not extracted as an array: ${JSON.stringify(
-            dependencies
-          )}`
-        );
-      }
-
       const identifierCountMap = new Map();
 
       let lastDep;
@@ -282,6 +277,8 @@ export function pitch(request) {
 
       if (!Array.isArray(exports)) {
         dependencies = [[null, exports]];
+      } else if (!emit) {
+        dependencies = exports;
       } else {
         dependencies = exports.map(([id, content, media, sourceMap]) => {
           const module = findModuleById(compilation, id);

test/__snapshots__/validate-loader-options.test.js.snap

@@ -1,5 +1,10 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
+exports[`validate options should throw an error on the "emit" option with "1" value 1`] = `
+"Invalid options object. Mini CSS Extract Plugin Loader has been initialized using an options object that does not match the API schema.
+ - options.emit should be a boolean."
+`;
+
 exports[`validate options should throw an error on the "esModule" option with "1" value 1`] = `
 "Invalid options object. Mini CSS Extract Plugin Loader has been initialized using an options object that does not match the API schema.
  - options.esModule should be a boolean."
@@ -29,47 +34,47 @@ exports[`validate options should throw an error on the "publicPath" option with
 exports[`validate options should throw an error on the "unknown" option with "/test/" value 1`] = `
 "Invalid options object. Mini CSS Extract Plugin Loader has been initialized using an options object that does not match the API schema.
  - options has an unknown property 'unknown'. These properties are valid:
-   object { publicPath?, esModule?, modules? }"
+   object { publicPath?, emit?, esModule?, modules? }"
 `;
 
 exports[`validate options should throw an error on the "unknown" option with "[]" value 1`] = `
 "Invalid options object. Mini CSS Extract Plugin Loader has been initialized using an options object that does not match the API schema.
  - options has an unknown property 'unknown'. These properties are valid:
-   object { publicPath?, esModule?, modules? }"
+   object { publicPath?, emit?, esModule?, modules? }"
 `;
 
 exports[`validate options should throw an error on the "unknown" option with "{"foo":"bar"}" value 1`] = `
 "Invalid options object. Mini CSS Extract Plugin Loader has been initialized using an options object that does not match the API schema.
  - options has an unknown property 'unknown'. These properties are valid:
-   object { publicPath?, esModule?, modules? }"
+   object { publicPath?, emit?, esModule?, modules? }"
 `;
 
 exports[`validate options should throw an error on the "unknown" option with "{}" value 1`] = `
 "Invalid options object. Mini CSS Extract Plugin Loader has been initialized using an options object that does not match the API schema.
  - options has an unknown property 'unknown'. These properties are valid:
-   object { publicPath?, esModule?, modules? }"
+   object { publicPath?, emit?, esModule?, modules? }"
 `;
 
 exports[`validate options should throw an error on the "unknown" option with "1" value 1`] = `
 "Invalid options object. Mini CSS Extract Plugin Loader has been initialized using an options object that does not match the API schema.
  - options has an unknown property 'unknown'. These properties are valid:
-   object { publicPath?, esModule?, modules? }"
+   object { publicPath?, emit?, esModule?, modules? }"
 `;
 
 exports[`validate options should throw an error on the "unknown" option with "false" value 1`] = `
 "Invalid options object. Mini CSS Extract Plugin Loader has been initialized using an options object that does not match the API schema.
  - options has an unknown property 'unknown'. These properties are valid:
-   object { publicPath?, esModule?, modules? }"
+   object { publicPath?, emit?, esModule?, modules? }"
 `;
 
 exports[`validate options should throw an error on the "unknown" option with "test" value 1`] = `
 "Invalid options object. Mini CSS Extract Plugin Loader has been initialized using an options object that does not match the API schema.
  - options has an unknown property 'unknown'. These properties are valid:
-   object { publicPath?, esModule?, modules? }"
+   object { publicPath?, emit?, esModule?, modules? }"
 `;
 
 exports[`validate options should throw an error on the "unknown" option with "true" value 1`] = `
 "Invalid options object. Mini CSS Extract Plugin Loader has been initialized using an options object that does not match the API schema.
  - options has an unknown property 'unknown'. These properties are valid:
-   object { publicPath?, esModule?, modules? }"
+   object { publicPath?, emit?, esModule?, modules? }"
 `;

test/validate-loader-options.test.js

@@ -6,6 +6,10 @@ describe('validate options', () => {
       success: ['/public/path/to/'],
       failure: [true],
     },
+    emit: {
+      success: [true, false],
+      failure: [1],
+    },
     esModule: {
       success: [true, false],
       failure: [1],