Add rule in order to enforce the declaration of a selector (#557)

* Add a new rule in order to enforce the declaration of a selector

Author: wKoza

src/enforceComponentSelectorRule.ts

@@ -0,0 +1,50 @@
+import * as Lint from 'tslint';
+import * as ts from 'typescript';
+import { sprintf } from 'sprintf-js';
+import { NgWalker } from './angular/ngWalker';
+import { ComponentMetadata } from './angular/metadata';
+
+export class Rule extends Lint.Rules.AbstractRule {
+
+    public static metadata: Lint.IRuleMetadata = {
+        ruleName: 'enforce-component-selector',
+        type: 'style',
+        description: 'Component selector must be declared.',
+        rationale: 'Omit the component selector makes debugging difficult.',
+        options: null,
+        optionsDescription: 'Not configurable.',
+        typescriptOnly: true
+    };
+
+
+    static SELECTOR_FAILURE: string = 'The selector of the component "%s" is mandatory.';
+
+    public apply(sourceFile: ts.SourceFile): Lint.RuleFailure[] {
+        return this.applyWithWalker(
+            new EnforceComponentSelectorValidatorWalker(sourceFile, this));
+    }
+}
+
+export class EnforceComponentSelectorValidatorWalker extends NgWalker {
+
+    constructor(sourceFile: ts.SourceFile, private rule: Rule) {
+        super(sourceFile, rule.getOptions());
+    }
+
+    visitNgComponent(metadata: ComponentMetadata) {
+        if (!metadata.selector) {
+            const failureConfig: string[] = [metadata.controller.name.text];
+            failureConfig.unshift(Rule.SELECTOR_FAILURE);
+            this.generateFailure(metadata.decorator.getStart(), metadata.decorator.getWidth(), failureConfig);
+        }
+        super.visitNgComponent(metadata);
+    }
+
+    private generateFailure(start: number, width: number, failureConfig: string[]) {
+        this.addFailure(
+            this.createFailure(
+                start,
+                width,
+                sprintf.apply(this, failureConfig)));
+    }
+}

src/index.ts

@@ -6,6 +6,7 @@ export { Rule as ContextualLifeCycleRule } from './contextualLifeCycleRule';
 export { Rule as DecoratorNotAllowedRule } from './decoratorNotAllowedRule';
 export { Rule as DirectiveClassSuffixRule } from './directiveClassSuffixRule';
 export { Rule as DirectiveSelectorRule } from './directiveSelectorRule';
+export { Rule as EnforceComponentSelectorRule} from './enforceComponentSelectorRule';
 export { Rule as I18nRule } from './i18nRule';
 export { Rule as ImportDestructuringSpacingRule } from './importDestructuringSpacingRule';
 export { Rule as MaxInlineDeclarationsRule } from './maxInlineDeclarationsRule';
@@ -31,6 +32,7 @@ export { Rule as UseOutputPropertyDecoratorRule } from './useOutputPropertyDecor
 export { Rule as UsePipeDecoratorRule } from './usePipeDecoratorRule';
 export { Rule as UsePipeTransformInterfaceRule } from './usePipeTransformInterfaceRule';
 export { Rule as UseViewEncapsulationRule } from './useViewEncapsulationRule';
+
 export * from './angular/config';
 
 // this file exists for tslint to resolve the rules directory

test/enforceComponentSelectorRule.spec.ts

@@ -0,0 +1,70 @@
+import { assertAnnotated, assertSuccess } from './testHelper';
+
+describe('enforceComoponentSelectorRule', () => {
+    it('should fail when selector is not given in @Component', () => {
+        let source = `
+      @Component()
+      ~~~~~~~~~~~~
+      class Test {}`;
+        assertAnnotated({
+            ruleName: 'enforce-component-selector',
+            message:  'The selector of the component "Test" is mandatory.',
+            source
+        });
+    });
+
+    it('should fail when selector is empty in @Component', () => {
+        let source = `
+      @Component({
+      ~~~~~~~~~~~~
+        selector: ''
+      })
+      ~~
+      class Test {}`;
+        assertAnnotated({
+            ruleName: 'enforce-component-selector',
+            message:  'The selector of the component "Test" is mandatory.',
+            source
+        });
+    });
+
+
+    it('should fail when selector equals 0 in @Component', () => {
+        let source = `
+      @Component({
+      ~~~~~~~~~~~~
+        selector: 0
+      })
+      ~~
+      class Test {}`;
+        assertAnnotated({
+            ruleName: 'enforce-component-selector',
+            message:  'The selector of the component "Test" is mandatory.',
+            source
+        });
+    });
+
+    it('should fail when selector equals null in @Component', () => {
+        let source = `
+      @Component({
+      ~~~~~~~~~~~~
+        selector: null
+      })
+      ~~
+      class Test {}`;
+        assertAnnotated({
+            ruleName: 'enforce-component-selector',
+            message:  'The selector of the component "Test" is mandatory.',
+            source
+        });
+    });
+
+    it('should succeed when selector is given in @Component', () => {
+        let source = `
+      @Component({
+        selector: 'sg-bar-foo'
+      })
+      class Test {}`;
+        assertSuccess('enforce-component-selector', source);
+    });
+});