fix(index): correct loader sourcemaps usage (#67)

* fix: pass sourcemaps to istanbul

package.json

@@ -8,6 +8,7 @@
     "dist"
   ],
   "dependencies": {
+    "convert-source-map": "^1.5.0",
     "istanbul-lib-instrument": "^1.7.3",
     "loader-utils": "^1.1.0"
   },
@@ -39,6 +40,7 @@
   "devDependencies": {
     "babel-cli": "^6.24.0",
     "babel-jest": "^20.0.3",
+    "babel-loader": "^7.1.1",
     "babel-plugin-transform-object-rest-spread": "^6.23.0",
     "babel-polyfill": "^6.23.0",
     "babel-preset-env": "^1.6.0",

src/index.js

@@ -1,11 +1,21 @@
 import { createInstrumenter } from 'istanbul-lib-instrument';
 import loaderUtils from 'loader-utils';
+import convert from 'convert-source-map';
+
+export default function (source, sourceMap) {
+  let srcMap = sourceMap;
+  // use inline source map, if any
+  if (!srcMap) {
+    const inlineSourceMap = convert.fromSource(source);
+    if (inlineSourceMap) {
+      srcMap = inlineSourceMap.sourcemap;
+    }
+  }
 
-export default function (source) {
   const options = Object.assign({ produceSourceMap: true }, loaderUtils.getOptions(this));
   const instrumenter = createInstrumenter(options);
 
   instrumenter.instrument(source, this.resourcePath, (error, instrumentedSource) => {
     this.callback(error, instrumentedSource, instrumenter.lastSourceMap());
-  });
+  }, srcMap);
 }

test/fixtures/basic.js

@@ -4,8 +4,4 @@ module.exports = class Foo {
     return !!this;
   }
 
-  baz() {
-    return !this.bar();
-  }
-
 };

test/index.test.js

@@ -9,7 +9,7 @@ test('instrument code', async () => {
 test('sourcemap files on by default', async () => {
   const stats = await webpack({
     extend: {
-      devtool: 'sourcemap',
+      devtool: 'source-map',
     },
   });
   const sourceMap = stats.compilation.assets['main.js.map'].source();
@@ -21,7 +21,7 @@ test('sourcemap files on by default', async () => {
 test('disabled sourcemaps', async () => {
   const stats = await webpack({
     extend: {
-      devtool: 'sourcemap',
+      devtool: 'source-map',
     },
     options: {
       produceSourceMap: false,

test/utils/loader.js

@@ -1,11 +1,18 @@
 import path from 'path';
 import loader from '../../src/cjs';
 
-module.exports = function (...args) {
+const normalize = str => str.split(path.sep).join('/');
+
+module.exports = function (source, map, ...args) {
   // hack the resourcePath to be consistent across systems so that tests always work
-  this.resourcePath = this.resourcePath
-    .replace(path.resolve(__dirname, '..'), '')
-    // make windows paths appear like unix
-    .replace(/\\/g, '/');
-  return loader.call(this, ...args);
+  this.resourcePath = normalize(this.resourcePath.replace(path.resolve(__dirname, '..'), ''));
+
+  // do the same hack for sourcemaps so tests are consistent
+  const sourceMap = map;
+  if (sourceMap) {
+    sourceMap.sourceRoot = '';
+    sourceMap.sources = sourceMap.sources.map(normalize);
+  }
+
+  return loader.call(this, source, sourceMap, ...args);
 };

test/utils/webpack.js

@@ -12,6 +12,9 @@ export default function ({ fixture = 'basic.js', options, extend = {} } = {}) {
     },
     module: {
       rules: [{
+        test: /\.js$/,
+        loader: 'babel-loader',
+      }, {
         test: /\.js$/,
         loader,
         enforce: 'post',