fix(instrumenter): only add header when there are mutants

packages/instrumenter/src/transformers/babel-transformer.ts

@@ -33,5 +33,7 @@ export const transformBabel: AstTransformer<AstFormat.JS | AstFormat.TS> = ({ ro
       }
     },
   });
-  root.program.body.unshift(...instrumentationBabelHeader);
+  if (mutantCollector.hasMutants(originFileName)) {
+    root.program.body.unshift(...instrumentationBabelHeader);
+  }
 };

packages/instrumenter/src/transformers/mutant-collector.ts

@@ -33,4 +33,8 @@ export class MutantCollector {
   public markMutantsAsPlaced(mutants: Mutant[]): void {
     this.unplacedMutants = this.unplacedMutants.filter((unplaced) => !mutants.includes(unplaced));
   }
+
+  public hasMutants(fileName: string) {
+    return this.mutants.some((mutant) => mutant.fileName === fileName);
+  }
 }

packages/instrumenter/test/unit/transformers/babel-transformer.spec.ts

@@ -82,12 +82,21 @@ describe('babel-transformer', () => {
 
   it('should add the global stuff on top', () => {
     const ast = createJSAst({ rawContent: 'foo' });
+    mutantCollectorMock.hasMutants.returns(true);
     transformBabel(ast, mutantCollectorMock, context);
     for (let i = 0; i < instrumentationBabelHeader.length; i++) {
       expect(ast.root.program.body[i]).eq(instrumentationBabelHeader[i]);
     }
   });
 
+  it('should not add global js header if no mutants were placed in the code', () => {
+    const ast = createJSAst({ originFileName: 'foo.js', rawContent: 'foo' });
+    mutantCollectorMock.hasMutants.returns(false);
+    transformBabel(ast, mutantCollectorMock, context);
+    expect(mutantCollectorMock.hasMutants).calledWith('foo.js');
+    expect(ast.root.program.body).lengthOf(1);
+  });
+
   describe('types', () => {
     it('should skip type annotations', () => {
       const ast = createTSAst({ rawContent: 'const foo: string;' });

packages/instrumenter/test/unit/transformers/mutant-collector.spec.ts

@@ -91,4 +91,23 @@ describe(MutantCollector.name, () => {
       expect(actual).deep.eq([mutants[1]]);
     });
   });
+
+  describe(MutantCollector.prototype.hasMutants.name, () => {
+    it('should return true when a mutant is registered for the file', () => {
+      const input = [createMutant({ fileName: 'foo.js' }), createMutant({ fileName: 'bar.js' })];
+      input.map((mutant) => sut.add(mutant.fileName, mutant));
+      expect(sut.hasMutants('foo.js')).true;
+      expect(sut.hasMutants('bar.js')).true;
+    });
+
+    it('should return false when no mutants is registered for the file', () => {
+      const input = [createMutant({ fileName: 'foo.js' }), createMutant({ fileName: 'bar.js' })];
+      input.map((mutant) => sut.add(mutant.fileName, mutant));
+      expect(sut.hasMutants('baz.js')).false;
+    });
+
+    it('should return false when no mutants are registered at all', () => {
+      expect(sut.hasMutants('baz.js')).false;
+    });
+  });
 });

packages/instrumenter/testResources/instrumenter/flow-typed.js.out.snap

@@ -1,61 +1,7 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
 exports[`instrumenter integration type declarations should not produce mutants for flow-types 1`] = `
-"function stryNS_9fa48() {
-  var g = new Function(\\"return this\\")();
-  var ns = g.__stryker__ || (g.__stryker__ = {});
-
-  if (ns.activeMutant === undefined && g.process && g.process.env && g.process.env.__STRYKER_ACTIVE_MUTANT__) {
-    ns.activeMutant = Number(g.process.env.__STRYKER_ACTIVE_MUTANT__);
-  }
-
-  function retrieveNS() {
-    return ns;
-  }
-
-  stryNS_9fa48 = retrieveNS;
-  return retrieveNS();
-}
-
-stryNS_9fa48();
-
-function stryCov_9fa48() {
-  var ns = stryNS_9fa48();
-  var cov = ns.mutantCoverage || (ns.mutantCoverage = {
-    static: {},
-    perTest: {}
-  });
-
-  function cover() {
-    var c = cov.static;
-
-    if (ns.currentTestId) {
-      c = cov.perTest[ns.currentTestId] = cov.perTest[ns.currentTestId] || {};
-    }
-
-    var a = arguments;
-
-    for (var i = 0; i < a.length; i++) {
-      c[a[i]] = (c[a[i]] || 0) + 1;
-    }
-  }
-
-  stryCov_9fa48 = cover;
-  cover.apply(null, arguments);
-}
-
-function stryMutAct_9fa48(id) {
-  var ns = stryNS_9fa48();
-
-  function isActive(id) {
-    return ns.activeMutant === id;
-  }
-
-  stryMutAct_9fa48 = isActive;
-  return isActive(id);
-}
-
-declare module 'react-test-renderer' {// eslint-disable-next-line no-inner-declarations
+"declare module 'react-test-renderer' {// eslint-disable-next-line no-inner-declarations
 }
 declare type ReactTestRenderer = {
   toJSON(): null | ReactTestRendererJSON,

packages/instrumenter/testResources/instrumenter/ts-declarations.ts.out.snap

@@ -1,61 +1,7 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
 exports[`instrumenter integration type declarations should not produce mutants for a TS declaration file 1`] = `
-"function stryNS_9fa48() {
-  var g = new Function(\\"return this\\")();
-  var ns = g.__stryker__ || (g.__stryker__ = {});
-
-  if (ns.activeMutant === undefined && g.process && g.process.env && g.process.env.__STRYKER_ACTIVE_MUTANT__) {
-    ns.activeMutant = Number(g.process.env.__STRYKER_ACTIVE_MUTANT__);
-  }
-
-  function retrieveNS() {
-    return ns;
-  }
-
-  stryNS_9fa48 = retrieveNS;
-  return retrieveNS();
-}
-
-stryNS_9fa48();
-
-function stryCov_9fa48() {
-  var ns = stryNS_9fa48();
-  var cov = ns.mutantCoverage || (ns.mutantCoverage = {
-    static: {},
-    perTest: {}
-  });
-
-  function cover() {
-    var c = cov.static;
-
-    if (ns.currentTestId) {
-      c = cov.perTest[ns.currentTestId] = cov.perTest[ns.currentTestId] || {};
-    }
-
-    var a = arguments;
-
-    for (var i = 0; i < a.length; i++) {
-      c[a[i]] = (c[a[i]] || 0) + 1;
-    }
-  }
-
-  stryCov_9fa48 = cover;
-  cover.apply(null, arguments);
-}
-
-function stryMutAct_9fa48(id) {
-  var ns = stryNS_9fa48();
-
-  function isActive(id) {
-    return ns.activeMutant === id;
-  }
-
-  stryMutAct_9fa48 = isActive;
-  return isActive(id);
-}
-
-export declare const globalNamespace = \\"globalNamespace\\";
+"export declare const globalNamespace = \\"globalNamespace\\";
 declare function foo(): 'foo';
 declare module 'express' {}"
 `;

packages/instrumenter/testResources/instrumenter/type-definitions.ts.out.snap

@@ -1,61 +1,7 @@
 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
 exports[`instrumenter integration type declarations should not produce mutants for TS type definitions 1`] = `
-"function stryNS_9fa48() {
-  var g = new Function(\\"return this\\")();
-  var ns = g.__stryker__ || (g.__stryker__ = {});
-
-  if (ns.activeMutant === undefined && g.process && g.process.env && g.process.env.__STRYKER_ACTIVE_MUTANT__) {
-    ns.activeMutant = Number(g.process.env.__STRYKER_ACTIVE_MUTANT__);
-  }
-
-  function retrieveNS() {
-    return ns;
-  }
-
-  stryNS_9fa48 = retrieveNS;
-  return retrieveNS();
-}
-
-stryNS_9fa48();
-
-function stryCov_9fa48() {
-  var ns = stryNS_9fa48();
-  var cov = ns.mutantCoverage || (ns.mutantCoverage = {
-    static: {},
-    perTest: {}
-  });
-
-  function cover() {
-    var c = cov.static;
-
-    if (ns.currentTestId) {
-      c = cov.perTest[ns.currentTestId] = cov.perTest[ns.currentTestId] || {};
-    }
-
-    var a = arguments;
-
-    for (var i = 0; i < a.length; i++) {
-      c[a[i]] = (c[a[i]] || 0) + 1;
-    }
-  }
-
-  stryCov_9fa48 = cover;
-  cover.apply(null, arguments);
-}
-
-function stryMutAct_9fa48(id) {
-  var ns = stryNS_9fa48();
-
-  function isActive(id) {
-    return ns.activeMutant === id;
-  }
-
-  stryMutAct_9fa48 = isActive;
-  return isActive(id);
-}
-
-/**
+"/**
  * @see https://github.com/stryker-mutator/stryker/issues/2465
  */
 const flatten = (require('lodash/flatten') as typeof import('lodash/flatten'));"