don't prefix output properties check rule (#440)

* don't prefix output properties check rule

* I18nRule export back

* Update index.ts

Author: eromano

README.md

@@ -208,6 +208,7 @@ Below you can find a recommended configuration which is based on the [Angular St
   "use-host-property-decorator": true,
   "no-attribute-parameter-decorator": true,
   "no-input-rename": true,
+  "no-on-prefix-output-name": true,
   "no-output-rename": true,
   "no-forward-ref": true,
   "use-life-cycle-interface": true,
@@ -292,6 +293,8 @@ module.exports = {
 [<img alt="leosvelperez" src="https://avatars0.githubusercontent.com/u/12051310?v=3&s=117" width="117">](https://github.com/leosvelperez) |[<img alt="rtfpessoa" src="https://avatars3.githubusercontent.com/u/902384?v=3&s=117" width="117">](https://github.com/rtfpessoa) |[<img alt="scttcper" src="https://avatars0.githubusercontent.com/u/1400464?v=3&s=117" width="117">](https://github.com/scttcper) |[<img alt="laco0416" src="https://avatars0.githubusercontent.com/u/1529180?v=3&s=117" width="117">](https://github.com/laco0416) |[<img alt="tmair" src="https://avatars1.githubusercontent.com/u/1596276?v=3&s=117" width="117">](https://github.com/tmair) |[<img alt="cexbrayat" src="https://avatars0.githubusercontent.com/u/411874?v=3&s=117" width="117">](https://github.com/cexbrayat) |
 :---: |:---: |:---: |:---: |:---: |:---: |
 [leosvelperez](https://github.com/leosvelperez) |[rtfpessoa](https://github.com/rtfpessoa) |[scttcper](https://github.com/scttcper) |[laco0416](https://github.com/laco0416) |[tmair](https://github.com/tmair) |[cexbrayat](https://github.com/cexbrayat) |
+[<img alt="eromano" src="https://avatars0.githubusercontent.com/u/1030050?v=3&s=117" width="117">](https://github.com/eromano) | | | | | |
+[eromano](https://github.com/eromano) | | | | ||
 
 ## License
 

docs/src/worker.ts

@@ -10,6 +10,7 @@ const rulesConfig = {
   'use-host-property-decorator': true,
   'no-input-rename': true,
   'no-output-rename': true,
+  'no-on-prefix-output-name': true,
   'use-life-cycle-interface': true,
   'use-pipe-transform-interface': true,
   'component-class-suffix': true,

package.json

@@ -23,7 +23,8 @@
   "contributors": [
     "Minko Gechev <[email protected]>",
     "Preslav Semov <[email protected]>",
-    "William Koza <[email protected]>"
+    "William Koza <[email protected]>",
+    "Eugenio Romano <[email protected]>"
   ],
   "repository": {
     "type": "git",

src/index.ts

@@ -11,6 +11,7 @@ export { Rule as ImportDestructuringSpacingRule } from './importDestructuringSpa
 export { Rule as NoAttributeParameterDecoratorRule } from './noAttributeParameterDecoratorRule';
 export { Rule as NoForwardRefRule } from './noForwardRefRule';
 export { Rule as NoInputRenameRule } from './noInputRenameRule';
+export { Rule as NoOutputOnPrefixNameRule } from './noOutputOnPrefixNameRule';
 export { Rule as NoOutputRenameRule } from './noOutputRenameRule';
 export { Rule as NoUnusedCssRule } from './noUnusedCssRule';
 export { Rule as PipeImpureRule } from './pipeImpureRule';

src/noOutputOnPrefixNameRule.ts

@@ -0,0 +1,44 @@
+import * as Lint from 'tslint';
+import * as ts from 'typescript';
+import { sprintf } from 'sprintf-js';
+import { NgWalker } from './angular/ngWalker';
+
+export class Rule extends Lint.Rules.AbstractRule {
+    public static metadata: Lint.IRuleMetadata = {
+        ruleName: 'no-on-prefix-output-name',
+        type: 'maintainability',
+        description: `Name events without the prefix on`,
+        descriptionDetails: `See more at https://angular.io/guide/styleguide#dont-prefix-output-properties`,
+        rationale: `Angular allows for an alternative syntax on-*. If the event itself was prefixed with on
+         this would result in an on-onEvent binding expression`,
+        options: null,
+        optionsDescription: `Not configurable.`,
+        typescriptOnly: true,
+    };
+
+    static FAILURE_STRING: string = 'In the class "%s", the output ' +
+        'property "%s" should not be prefixed with on';
+
+    public apply(sourceFile: ts.SourceFile): Lint.RuleFailure[] {
+        return this.applyWithWalker(
+            new OutputWalker(sourceFile,
+                this.getOptions()));
+    }
+}
+
+export class OutputWalker extends NgWalker {
+    visitNgOutput(property: ts.PropertyDeclaration, output: ts.Decorator, args: string[]) {
+      let className = (<any>property).parent.name.text;
+      let memberName = (<any>property.name).text;
+
+      if (memberName && memberName.startsWith('on')) {
+            let failureConfig: string[] = [className, memberName];
+            failureConfig.unshift(Rule.FAILURE_STRING);
+            this.addFailure(
+                this.createFailure(
+                    property.getStart(),
+                    property.getWidth(),
+                    sprintf.apply(this, failureConfig)));
+        }
+    }
+}

test/noOutputOnPrefixNameRule.spec.ts

@@ -0,0 +1,27 @@
+import { assertSuccess, assertAnnotated } from './testHelper';
+
+describe('no-on-prefix-output-name', () => {
+  describe('invalid directive output property', () => {
+    it(`should fail, when a directive output property is named with on prefix`, () => {
+      let source = `
+      class ButtonComponent {
+        @Output() onChange = new EventEmitter<any>();
+        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+      }`;
+      assertAnnotated({
+        ruleName: 'no-on-prefix-output-name',
+        source
+      });
+    });
+  });
+
+  describe('valid directive output property', () => {
+    it('should succeed, when a directive output property is properly named', () => {
+      let source = `
+      class ButtonComponent {
+         @Output() change = new EventEmitter<any>();
+      }`;
+      assertSuccess('no-on-prefix-output-name', source);
+    });
+  });
+});