fix(loader): pass emitFile to the child compilation (loaderContext.emitFile)

src/index.js

@@ -146,6 +146,7 @@ class MiniCssExtractPlugin {
               )}`
             );
           }
+
           const identifierCountMap = new Map();
           for (const line of content) {
             const count = identifierCountMap.get(line.identifier) || 0;

src/loader.js

@@ -59,6 +59,7 @@ export function pitch(request) {
       compilation.hooks.normalModuleLoader.tap(
         `${pluginName} loader`,
         (loaderContext, module) => {
+          loaderContext.emitFile = this.emitFile;
           loaderContext[MODULE_TYPE] = false; // eslint-disable-line no-param-reassign
           if (module.request === request) {
             // eslint-disable-next-line no-param-reassign

test/TestMemoryFS.test.js

@@ -0,0 +1,39 @@
+import path from 'path';
+
+import MemoryFS from 'memory-fs';
+import webpack from 'webpack';
+
+const assetsNames = (json) => json.assets.map((asset) => asset.name);
+
+describe('TestMemoryFS', () => {
+  it('should preserve asset even if not emitted', (done) => {
+    const casesDirectory = path.resolve(__dirname, 'cases');
+    const directoryForCase = path.resolve(casesDirectory, 'simple-publicpath');
+    const webpackConfig = require(path.resolve(
+      directoryForCase,
+      'webpack.config.js'
+    ));
+    const compiler = webpack({
+      ...webpackConfig,
+      mode: 'development',
+      context: directoryForCase,
+    });
+    compiler.outputFileSystem = new MemoryFS();
+    compiler.run((err1, stats1) => {
+      if (err1) {
+        done(err1);
+        return;
+      }
+      compiler.run((err2, stats2) => {
+        if (err2) {
+          done(err2);
+          return;
+        }
+        expect(assetsNames(stats1.toJson())).toEqual(
+          assetsNames(stats2.toJson())
+        );
+        done();
+      });
+    });
+  });
+});