fix: don't prepend the webpack context to absolute source roots

Fixes #33

src/util.js

@@ -26,7 +26,13 @@ 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)) {
+  if (
+    webpackConfig &&
+    webpackConfig.context &&
+    sourceMap.sourceRoot &&
+    !sourceMap.sourceRoot.startsWith(webpackConfig.context) &&
+    !path.isAbsolute(sourceMap.sourceRoot)
+  ) {
     sourceRoot = path.join(webpackConfig.context, sourceRoot);
   }
 

test/util.spec.js

@@ -142,5 +142,22 @@ describe('util', () => {
         context: '/Users/mattlewis/Code/open-source/karma-coverage-istanbul-reporter/test/fixtures/typescript'
       })).to.deep.equal(output);
     });
+
+    it('should not the webpack context to the source root if the source root is absolute', () => {
+      const input = {
+        file: 'example.ts',
+        sourceRoot: '/Users/mattlewis/Code/open-source/karma-coverage-istanbul-reporter/test/fixtures/typescript',
+        sources: ['example.ts']
+      };
+
+      const output = {
+        file: 'example.ts',
+        sourceRoot: '/Users/mattlewis/Code/open-source/karma-coverage-istanbul-reporter/test/fixtures/typescript',
+        sources: ['example.ts']
+      };
+      expect(fixWebpackSourcePaths(input, {
+        context: '/Users/mattlewis/Code/open-source/karma-coverage-istanbul-reporter/test/fixtures/typescript/src'
+      })).to.deep.equal(output);
+    });
   });
 });