feat: add arrow function property mutator

packages/javascript-mutator/src/mutators/ArrowFunctionPropertyMutator.ts

@@ -0,0 +1,25 @@
+import * as types from '@babel/types';
+
+import { NodeGenerator } from '../helpers/NodeGenerator';
+
+import { NodeMutator } from './NodeMutator';
+
+/**
+ * Represents a mutator which can mutate an object shorthand property.
+ */
+export default class ArrowFunctionPropertyMutator implements NodeMutator {
+  public name = 'ArrowFunctionProperty';
+
+  public mutate(node: types.Node): Array<[types.Node, types.Node | { raw: string }]> {
+    return types.isObjectPattern(node)
+      ? node.properties
+          .filter((prop) => types.isObjectProperty(prop) && prop.shorthand)
+          .map((mutateProp) => [
+            node,
+            NodeGenerator.createMutatedCloneWithProperties(node, {
+              properties: node.properties.filter((prop) => prop !== mutateProp),
+            }),
+          ])
+      : [];
+  }
+}

packages/javascript-mutator/src/mutators/index.ts

@@ -1,6 +1,7 @@
 import ArithmeticOperatorMutator from './ArithmeticOperatorMutator';
 import ArrayDeclarationMutator from './ArrayDeclarationMutator';
 import ArrowFunctionMutator from './ArrowFunctionMutator';
+import ArrowFunctionPropertyMutator from './ArrowFunctionPropertyMutator';
 import BlockStatementMutator from './BlockStatementMutator';
 import BooleanLiteralMutator from './BooleanLiteralMutator';
 import ConditionalExpressionMutator from './ConditionalExpressionMutator';
@@ -15,6 +16,7 @@ export const nodeMutators = Object.freeze([
   new ArithmeticOperatorMutator(),
   new ArrayDeclarationMutator(),
   new ArrowFunctionMutator(),
+  new ArrowFunctionPropertyMutator(),
   new BlockStatementMutator(),
   new BooleanLiteralMutator(),
   new ConditionalExpressionMutator(),

packages/javascript-mutator/test/unit/mutators/ArrowFunctionPropertyMutator.spec.ts

@@ -0,0 +1,6 @@
+import ArrowFunctionPropertyMutatorSpec from '@stryker-mutator/mutator-specification/src/ArrowFunctionPropertyMutatorSpec';
+
+import ArrowFunctionPropertyMutator from '../../../src/mutators/ArrowFunctionPropertyMutator';
+import { verifySpecification } from '../../helpers/mutatorAssertions';
+
+verifySpecification(ArrowFunctionPropertyMutatorSpec, ArrowFunctionPropertyMutator);

packages/mutator-specification/src/ArrowFunctionPropertyMutatorSpec.ts

@@ -0,0 +1,23 @@
+import { expect } from 'chai';
+
+import ExpectMutation from './ExpectMutation';
+
+export default function ArrowFunctionPropertyMutatorSpec(name: string, expectMutation: ExpectMutation) {
+  describe('ArrowFunctionPropertyMutator', () => {
+    it('should have name "ArrowFunctionProperty"', () => {
+      expect(name).eq('ArrowFunctionProperty');
+    });
+
+    it('should mutate a single object property in an arrow function expression', () => {
+      expectMutation('({ bar }) => baz', '({}) => baz');
+    });
+
+    it('should mutate multiple object shorthand properties in an arrow function expression', () => {
+      expectMutation('({ bar, baz = "qux" }) => baz', '({ baz = "qux" }) => baz', '({ bar }) => baz');
+    });
+
+    it('shoud not mutate empty properties in an arrow function expression', () => {
+      expectMutation('({}) => baz');
+    });
+  });
+}

packages/mutator-specification/src/index.ts

@@ -1,6 +1,7 @@
 export { default as ArithmeticOperatorMutatorSpec } from './ArithmeticOperatorMutatorSpec';
 export { default as ArrayDeclarationMutatorSpec } from './ArrayDeclarationMutatorSpec';
 export { default as ArrowFunctionMutatorSpec } from './ArrowFunctionMutatorSpec';
+export { default as ArrowFunctionPropertyMutatorSpec } from './ArrowFunctionPropertyMutatorSpec';
 export { default as BlockStatementMutatorSpec } from './BlockStatementMutatorSpec';
 export { default as BooleanLiteralMutatorSpec } from './BooleanLiteralMutatorSpec';
 export { default as ConditionalExpressionMutatorSpec } from './ConditionalExpressionMutatorSpec';