fix(duplicate files): make transpile always result in unique file nam…

…es (#1405)

Make sure that the typescript transpiler plugin always results in unique
file names. For example, given the following input:

```
foo.js
foo.ts
```

It will transpile `foo.ts` to `foo.js`, the result is now:

```
foo.js
```

packages/typescript/src/TypescriptTranspiler.ts

@@ -1,4 +1,3 @@
-import flatMap = require('lodash.flatmap');
 import * as ts from 'typescript';
 import { Transpiler } from '@stryker-mutator/api/transpile';
 import { File, StrykerOptions } from '@stryker-mutator/api/core';
@@ -31,7 +30,7 @@ export default class TypescriptTranspiler implements Transpiler {
     if (error.length) {
       return Promise.reject(new Error(error));
     } else {
-      const resultFiles: File[] = this.transpileFiles(files);
+      const resultFiles = this.transpileFiles(files);
       return Promise.resolve(resultFiles);
     }
   }
@@ -47,23 +46,27 @@ export default class TypescriptTranspiler implements Transpiler {
       compilerOptions, typescriptFiles, getProjectDirectory(this.options), this.produceSourceMaps, this.getLogger);
   }
 
-  private transpileFiles(files: ReadonlyArray<File>) {
+  private transpileFiles(files: ReadonlyArray<File>): ReadonlyArray<File> {
     let isSingleOutput = false;
-    // Keep original order of the files using a flatmap.
-    return flatMap(files, file => {
-      if (!isHeaderFile(file.name) && this.filter.isIncluded(file.name)) {
-        // File is to be transpiled. Only emit if more output is expected.
-        if (isSingleOutput) {
-          return [];
-        } else {
-          const emitOutput = this.languageService.emit(file.name);
-          isSingleOutput = emitOutput.singleResult;
-          return emitOutput.outputFiles;
+    const fileDictionary: { [name: string]: File } = {};
+    files.forEach(file => fileDictionary[file.name] = file);
+    files.forEach(file => {
+      if (!isHeaderFile(file.name)) {
+        if (this.filter.isIncluded(file.name)) {
+
+          // File is to be transpiled. Only emit if more output is expected.
+          if (!isSingleOutput) {
+            const emitOutput = this.languageService.emit(file.name);
+            isSingleOutput = emitOutput.singleResult;
+            emitOutput.outputFiles.forEach(file => fileDictionary[file.name] = file);
+          }
+
+          // Remove original file
+          delete fileDictionary[file.name];
         }
-      } else {
-        // File is not an included typescript file
-        return [file];
       }
     });
+
+    return Object.keys(fileDictionary).map(name => fileDictionary[name]);
   }
 }

packages/typescript/test/unit/TypescriptTranspiler.spec.ts

@@ -9,7 +9,7 @@ import sinon = require('sinon');
 import { testInjector } from '@stryker-mutator/test-helpers';
 import { commonTokens } from '@stryker-mutator/api/plugin';
 
-describe('TypescriptTranspiler', () => {
+describe(TypescriptTranspiler.name, () => {
 
   let languageService: sinon.SinonStubbedInstance<TranspilingLanguageService>;
   let sut: TypescriptTranspiler;
@@ -96,35 +96,20 @@ describe('TypescriptTranspiler', () => {
       expect(languageService.emit).calledWith('file1.ts');
     });
 
-    it('should keep order if single output result file', async () => {
+    it('should remove duplicate files (issue 1318)', async () => {
       // Arrange
-      const input = [
-        new File('file1.ts', 'file1'),
-        new File('file2.ts', 'file2'),
-        new File('file3.bin', Buffer.from([1, 2, 3])),
-        new File('file4.ts', 'file4'),
-        new File('file5.ts', 'file5')
-      ];
-      const allOutput = new File('allOutput.js', 'single output');
-      const emitResult: EmitOutput = {
-        outputFiles: [allOutput],
-        singleResult: true
-      };
-      languageService.emit.returns(emitResult);
-      arrangeIncludedFiles([input[1], input[3]]);
+      const inputFile = new File('file1.ts', 'const foo: number = 42;');
+      const expectedOutputFile = new File('file1.js', 'const foo = 42;');
+      arrangeIncludedFiles([inputFile]);
+      const input = [inputFile, new File('file1.js', 'js content')];
+      languageService.emit.returns(multiResult(expectedOutputFile));
 
       // Act
       const outputFiles = await sut.transpile(input);
 
       // Assert
-      expectFilesEqual(outputFiles, [
-        new File('file1.ts', 'file1'),
-        allOutput,
-        new File('file3.bin', Buffer.from([1, 2, 3])),
-        new File('file5.ts', 'file5')
-      ]);
-      expect(languageService.emit).calledOnce;
-      expect(languageService.emit).calledWith('file2.ts');
+      expect(outputFiles).lengthOf(1);
+      expect(outputFiles[0]).eq(expectedOutputFile);
     });
 
     it('should reject errors when there are diagnostic messages', async () => {
@@ -136,7 +121,11 @@ describe('TypescriptTranspiler', () => {
   });
 
   function expectFilesEqual(actual: ReadonlyArray<File>, expected: ReadonlyArray<File>) {
-    expect(serialize(actual)).eq(serialize(expected));
+    expect(serialize(orderByName(actual))).eq(serialize(orderByName(expected)));
+  }
+
+  function orderByName(files: ReadonlyArray<File>) {
+    files.slice().sort((a, b) => a.name.localeCompare(b.name));
   }
 
   function multiResult(file: File): EmitOutput {