feat(rule): add pipe-prefix rule

src/index.ts

@@ -24,6 +24,7 @@ export { Rule as NoTemplateCallExpressionRule } from './noTemplateCallExpression
 export { Rule as NoUnusedCssRule } from './noUnusedCssRule';
 export { Rule as PipeImpureRule } from './pipeImpureRule';
 export { Rule as PipeNamingRule } from './pipeNamingRule';
+export { Rule as PipePrefixRule } from './pipePrefixRule';
 export { Rule as PreferInlineDecorator } from './preferInlineDecoratorRule';
 export { Rule as PreferOutputReadonlyRule } from './preferOutputReadonlyRule';
 export { Rule as TemplateConditionalComplexityRule } from './templateConditionalComplexityRule';

src/pipeNamingRule.ts

@@ -11,7 +11,7 @@ const OPTION_KEBAB_CASE = 'kebab-case';
 
 export class Rule extends Lint.Rules.AbstractRule {
   static readonly metadata: Lint.IRuleMetadata = {
-    deprecationMessage: `You can name your pipes only ${OPTION_CAMEL_CASE}. If you try to use snake-case then your application will not compile.`,
+    deprecationMessage: `You can name your pipes only ${OPTION_CAMEL_CASE}. If you try to use snake-case then your application will not compile. For prefix validation use pipe-prefix rule.`,
     description: 'Enforce consistent case and prefix for pipes.',
     optionExamples: [
       [true, OPTION_CAMEL_CASE, 'myPrefix'],

src/pipePrefixRule.ts

@@ -0,0 +1,98 @@
+import { sprintf } from 'sprintf-js';
+import * as Lint from 'tslint';
+import * as ts from 'typescript';
+import { NgWalker } from './angular/ngWalker';
+import { SelectorValidator } from './util/selectorValidator';
+import { getDecoratorArgument } from './util/utils';
+
+export class Rule extends Lint.Rules.AbstractRule {
+  static readonly metadata: Lint.IRuleMetadata = {
+    description: 'Enforce consistent prefix for pipes.',
+    optionExamples: [[true, 'myPrefix'], [true, 'myPrefix', 'myOtherPrefix']],
+    options: {
+      items: [
+        {
+          type: 'string'
+        }
+      ],
+      minLength: 1,
+      type: 'array'
+    },
+    optionsDescription: Lint.Utils.dedent`
+      * The list of arguments are supported prefixes (given as strings).
+    `,
+    rationale: 'Consistent conventions make it easy to quickly identify and reference assets of different types.',
+    ruleName: 'pipe-prefix',
+    type: 'style',
+    typescriptOnly: true
+  };
+
+  static FAILURE_STRING = `The name of the Pipe decorator of class %s should start with prefix %s, however its value is "%s"`;
+
+  prefix: string;
+  private prefixChecker: Function;
+
+  constructor(options: Lint.IOptions) {
+    super(options);
+
+    let args = options.ruleArguments;
+    if (!(args instanceof Array)) {
+      args = [args];
+    }
+    this.prefix = args.join(',');
+    let prefixExpression = args.join('|');
+    this.prefixChecker = SelectorValidator.prefix(prefixExpression, 'camelCase');
+  }
+
+  apply(sourceFile: ts.SourceFile): Lint.RuleFailure[] {
+    return this.applyWithWalker(new ClassMetadataWalker(sourceFile, this));
+  }
+
+  isEnabled(): boolean {
+    const {
+      metadata: {
+        options: { minLength }
+      }
+    } = Rule;
+    const { length } = this.ruleArguments;
+
+    return super.isEnabled() && length >= minLength;
+  }
+
+  validatePrefix(prefix: string): boolean {
+    return this.prefixChecker(prefix);
+  }
+}
+
+export class ClassMetadataWalker extends NgWalker {
+  constructor(sourceFile: ts.SourceFile, private rule: Rule) {
+    super(sourceFile, rule.getOptions());
+  }
+
+  protected visitNgPipe(controller: ts.ClassDeclaration, decorator: ts.Decorator) {
+    let className = controller.name!.text;
+    this.validateProperties(className, decorator);
+    super.visitNgPipe(controller, decorator);
+  }
+
+  private validateProperties(className: string, pipe: ts.Decorator) {
+    const argument = getDecoratorArgument(pipe)!;
+
+    argument.properties
+      .filter(p => p.name && ts.isIdentifier(p.name) && p.name.text === 'name')
+      .forEach(this.validateProperty.bind(this, className));
+  }
+
+  private validateProperty(className: string, property: ts.Node) {
+    const initializer = ts.isPropertyAssignment(property) ? property.initializer : undefined;
+
+    if (initializer && ts.isStringLiteral(initializer)) {
+      const propName = initializer.text;
+      const isValid = this.rule.validatePrefix(propName);
+
+      if (!isValid) {
+        this.addFailureAtNode(property, sprintf(Rule.FAILURE_STRING, className, this.rule.prefix, propName));
+      }
+    }
+  }
+}

test/pipePrefixRule.spec.ts

@@ -0,0 +1,104 @@
+import { assertSuccess, assertAnnotated } from './testHelper';
+
+describe('pipe-prefix', () => {
+  describe('invalid pipe name', () => {
+    it('should fail when Pipe has no prefix ng', () => {
+      let source = `
+        @Pipe({
+          name: 'foo-bar'
+          ~~~~~~~~~~~~~~~
+        })
+        class Test {}
+      `;
+      assertAnnotated({
+        ruleName: 'pipe-prefix',
+        message: 'The name of the Pipe decorator of class Test should start with prefix ng, however its value is "foo-bar"',
+        source,
+        options: ['ng']
+      });
+    });
+
+    it('should fail when Pipe has no prefix applying multiple prefixes', () => {
+      let source = `
+        @Pipe({
+          name: 'foo-bar'
+          ~~~~~~~~~~~~~~~
+        })
+        class Test {}
+      `;
+      assertAnnotated({
+        ruleName: 'pipe-prefix',
+        message: 'The name of the Pipe decorator of class Test should start' + ' with prefix ng,mg,sg, however its value is "foo-bar"',
+        source,
+        options: ['ng', 'mg', 'sg']
+      });
+    });
+  });
+
+  describe('empty pipe', () => {
+    it('should not fail when @Pipe not invoked', () => {
+      let source = `
+        @Pipe
+        class Test {}
+      `;
+      assertSuccess('pipe-prefix', source, ['ng']);
+    });
+  });
+
+  describe('pipe with name as variable', () => {
+    it('should ignore the rule when the name is a variable', () => {
+      const source = `
+        export function mockPipe(name: string): any {
+          @Pipe({ name })
+          class MockPipe implements PipeTransform {
+            transform(input: any): any {
+              return input;
+            }
+          }
+          return MockPipe;
+        }
+      `;
+      assertSuccess('pipe-prefix', source, ['ng']);
+    });
+  });
+
+  describe('valid pipe name', () => {
+    it('should succeed with prefix ng in @Pipe', () => {
+      let source = `
+        @Pipe({
+          name: 'ngBarFoo'
+        })
+        class Test {}
+      `;
+      assertSuccess('pipe-prefix', source, ['ng']);
+    });
+
+    it('should succeed with multiple prefixes in @Pipe', () => {
+      let source = `
+        @Pipe({
+          name: 'ngBarFoo'
+        })
+        class Test {}
+      `;
+      assertSuccess('pipe-prefix', source, ['ng', 'sg', 'mg']);
+    });
+
+    it('should succeed when the class is not a Pipe', () => {
+      let source = `
+        class Test {}
+      `;
+      assertSuccess('pipe-prefix', source, ['ng']);
+    });
+
+    it('should do nothing if the name of the pipe is not a literal', () => {
+      let source = `
+        const pipeName = 'fooBar';
+        @Pipe({
+          name: pipeName
+        })
+        class Test {}
+      `;
+      assertSuccess('pipe-prefix', source, ['ng']);
+    });
+  });
+});