fix: prepend the webpack context to the source root if not set

Closes #32

src/reporter.js

@@ -61,7 +61,7 @@ function CoverageIstanbulReporter(baseReporterDecorator, logger, config) {
       Object.keys(coverage).forEach(filename => {
         const fileCoverage = coverage[filename];
         if (fileCoverage.inputSourceMap && coverageIstanbulReporter.fixWebpackSourcePaths) {
-          fileCoverage.inputSourceMap = util.fixWebpackSourcePaths(fileCoverage.inputSourceMap);
+          fileCoverage.inputSourceMap = util.fixWebpackSourcePaths(fileCoverage.inputSourceMap, config.webpack);
         }
         if (
           coverageIstanbulReporter.skipFilesWithNoCoverage &&

src/util.js

@@ -22,8 +22,16 @@ function fixWebpackFilePath(filePath) {
   return filePath;
 }
 
-function fixWebpackSourcePaths(sourceMap) {
+function fixWebpackSourcePaths(sourceMap, webpackConfig) {
+  let sourceRoot = sourceMap.sourceRoot;
+  // Fix for https://github.com/mattlewis92/karma-coverage-istanbul-reporter/issues/32
+  // The sourceRoot is relative to the project directory and not an absolute path, so add the webpack context to it if set
+  if (webpackConfig && webpackConfig.context && sourceMap.sourceRoot && !sourceMap.sourceRoot.startsWith(webpackConfig.context)) {
+    sourceRoot = path.join(webpackConfig.context, sourceRoot);
+  }
+
   return Object.assign({}, sourceMap, {
+    sourceRoot: sourceRoot, // eslint-disable-line object-shorthand
     sources: (sourceMap.sources || []).map(source => {
       source = fixWebpackFilePath(source);
       if (sourceMap.sourceRoot && source.startsWith(sourceMap.sourceRoot)) {

test/util.spec.js

@@ -108,5 +108,39 @@ describe('util', () => {
 
       expect(fixWebpackSourcePaths(input)).to.deep.equal(output);
     });
+
+    it('should add the webpack context to the source root if not set', () => {
+      const input = {
+        file: 'example.ts',
+        sourceRoot: 'src',
+        sources: ['example.ts']
+      };
+
+      const output = {
+        file: 'example.ts',
+        sourceRoot: '/Users/mattlewis/Code/open-source/karma-coverage-istanbul-reporter/test/fixtures/typescript/src',
+        sources: ['example.ts']
+      };
+      expect(fixWebpackSourcePaths(input, {
+        context: '/Users/mattlewis/Code/open-source/karma-coverage-istanbul-reporter/test/fixtures/typescript'
+      })).to.deep.equal(output);
+    });
+
+    it('should only add the webpack context to the source root if not already set', () => {
+      const input = {
+        file: 'example.ts',
+        sourceRoot: '/Users/mattlewis/Code/open-source/karma-coverage-istanbul-reporter/test/fixtures/typescript/src',
+        sources: ['example.ts']
+      };
+
+      const output = {
+        file: 'example.ts',
+        sourceRoot: '/Users/mattlewis/Code/open-source/karma-coverage-istanbul-reporter/test/fixtures/typescript/src',
+        sources: ['example.ts']
+      };
+      expect(fixWebpackSourcePaths(input, {
+        context: '/Users/mattlewis/Code/open-source/karma-coverage-istanbul-reporter/test/fixtures/typescript'
+      })).to.deep.equal(output);
+    });
   });
 });