Refer to the entry point instead of the first module for default identifier

The order of modules can be reordered by optimize-module-order plugins.
The intention is to use the entry point as the default identifier, so
refer to entries property of the compilation.

Author: akihikodaki

src/loader.js

@@ -94,13 +94,16 @@ export function pitch(request) {
       }
       try {
         let text = this.exec(source, request);
-        if (typeof text === 'string') { text = [[0, text]]; }
-        text.forEach((item) => {
-          const id = item[0];
-          compilation.modules.forEach((module) => {
-            if (module.id === id) { item[0] = module.identifier(); }
+        if (typeof text === 'string') {
+          text = [[compilation.entries[0].identifier(), text]];
+        } else {
+          text.forEach((item) => {
+            const id = item[0];
+            compilation.modules.forEach((module) => {
+              if (module.id === id) { item[0] = module.identifier(); }
+            });
           });
-        });
+        }
         this[NS](text, query);
         if (text.locals && typeof resultSource !== 'undefined') {
           resultSource += `\nmodule.exports = ${JSON.stringify(text.locals)};`;

test/__snapshots__/webpack-integration.test.js.snap

@@ -160,3 +160,9 @@ exports[`Webpack Integration Tests splitted-chunk 1`] = `
 exports[`Webpack Integration Tests splitted-multiple-entries 1`] = `""`;
 
 exports[`Webpack Integration Tests splitted-multiple-entries 2`] = `""`;
+
+exports[`Webpack Integration Tests string-export-with-optimize-module-order 1`] = `
+"a
+b
+"
+`;

test/cases/string-export-with-optimize-module-order/a.js

@@ -0,0 +1,2 @@
+require("./module")();
+module.exports = "a\n";

test/cases/string-export-with-optimize-module-order/b.js

@@ -0,0 +1,2 @@
+require("./module")();
+module.exports = "b\n";

test/cases/string-export-with-optimize-module-order/expected/main.txt

@@ -0,0 +1,2 @@
+a
+b

test/cases/string-export-with-optimize-module-order/loader.js

@@ -0,0 +1,3 @@
+module.exports = function(source) {
+  return source;
+}

test/cases/string-export-with-optimize-module-order/module.js

@@ -0,0 +1 @@
+module.exports = () => {};

test/cases/string-export-with-optimize-module-order/webpack.config.js

@@ -0,0 +1,26 @@
+import ExtractTextPlugin from '../../../src/index';
+
+function moduleOrderOptimizer() {
+  this.plugin("after-plugins", compiler =>
+    compiler.plugin("compilation", compilation =>
+      compilation.plugin("optimize-module-order", modules => {
+        const index = modules.findIndex(module => module.rawRequest == "./module");
+        [modules[0], modules[index]] = [modules[index], modules[0]];
+      })));
+}
+
+module.exports = {
+  entry: ['./a', './b'],
+  module: {
+    loaders: [
+      {
+        test: /(a|b)\.js$/,
+        use: ExtractTextPlugin.extract('./loader')
+      },
+    ],
+  },
+  plugins: [
+    moduleOrderOptimizer,
+    new ExtractTextPlugin('[name].txt'),
+  ],
+};