feat(eslint-plugin-template): [self-closing-tags] add rule (#1322)

packages/eslint-plugin-template/docs/rules/prefer-self-closing-tags.md

@@ -0,0 +1,263 @@
+<!--
+
+  DO NOT EDIT.
+
+  This markdown file was autogenerated using a mixture of the following files as the source of truth for its data:
+  - ../../src/rules/prefer-self-closing-tags.ts
+  - ../../tests/rules/prefer-self-closing-tags/cases.ts
+
+  In order to update this file, it is therefore those files which need to be updated, as well as potentially the generator script:
+  - ../../../../tools/scripts/generate-rule-docs.ts
+
+-->
+
+<br>
+
+# `@angular-eslint/template/prefer-self-closing-tags`
+
+Ensures that self-closing tags are used for elements with a closing tag but no content.
+
+- Type: layout
+- 🔧 Supports autofix (`--fix`)
+
+<br>
+
+## Rule Options
+
+The rule does not have any configuration options.
+
+<br>
+
+## Usage Examples
+
+> The following examples are generated automatically from the actual unit tests within the plugin, so you can be assured that their behavior is accurate based on the current commit.
+
+<br>
+
+<details>
+<summary>❌ - Toggle examples of <strong>incorrect</strong> code for this rule</summary>
+
+<br>
+
+#### Default Config
+
+```json
+{
+  "rules": {
+    "@angular-eslint/template/prefer-self-closing-tags": [
+      "error"
+    ]
+  }
+}
+```
+
+<br>
+
+#### ❌ Invalid Code
+
+```html
+<my-component></my-component>
+              ~~~~~~~~~~~~~~~
+```
+
+<br>
+
+---
+
+<br>
+
+#### Default Config
+
+```json
+{
+  "rules": {
+    "@angular-eslint/template/prefer-self-closing-tags": [
+      "error"
+    ]
+  }
+}
+```
+
+<br>
+
+#### ❌ Invalid Code
+
+```html
+<my-component type="text" [name]="foo"></my-component>
+                                       ~~~~~~~~~~~~~~~
+```
+
+<br>
+
+---
+
+<br>
+
+#### Default Config
+
+```json
+{
+  "rules": {
+    "@angular-eslint/template/prefer-self-closing-tags": [
+      "error"
+    ]
+  }
+}
+```
+
+<br>
+
+#### ❌ Invalid Code
+
+```html
+<my-component
+  type="text"
+  [name]="foo"
+  [items]="items">
+</my-component>
+~~~~~~~~~~~~~~~
+```
+
+</details>
+
+<br>
+
+---
+
+<br>
+
+<details>
+<summary>✅ - Toggle examples of <strong>correct</strong> code for this rule</summary>
+
+<br>
+
+#### Default Config
+
+```json
+{
+  "rules": {
+    "@angular-eslint/template/prefer-self-closing-tags": [
+      "error"
+    ]
+  }
+}
+```
+
+<br>
+
+#### ✅ Valid Code
+
+```html
+<my-component type="text" [name]="foo">With some content</my-component>
+```
+
+<br>
+
+---
+
+<br>
+
+#### Default Config
+
+```json
+{
+  "rules": {
+    "@angular-eslint/template/prefer-self-closing-tags": [
+      "error"
+    ]
+  }
+}
+```
+
+<br>
+
+#### ✅ Valid Code
+
+```html
+<my-component />
+```
+
+<br>
+
+---
+
+<br>
+
+#### Default Config
+
+```json
+{
+  "rules": {
+    "@angular-eslint/template/prefer-self-closing-tags": [
+      "error"
+    ]
+  }
+}
+```
+
+<br>
+
+#### ✅ Valid Code
+
+```html
+<my-component
+  type="text"
+  [name]="foo"
+  [items]="items" />
+```
+
+<br>
+
+---
+
+<br>
+
+#### Default Config
+
+```json
+{
+  "rules": {
+    "@angular-eslint/template/prefer-self-closing-tags": [
+      "error"
+    ]
+  }
+}
+```
+
+<br>
+
+#### ✅ Valid Code
+
+```html
+<img />
+```
+
+<br>
+
+---
+
+<br>
+
+#### Default Config
+
+```json
+{
+  "rules": {
+    "@angular-eslint/template/prefer-self-closing-tags": [
+      "error"
+    ]
+  }
+}
+```
+
+<br>
+
+#### ✅ Valid Code
+
+```html
+<div></div>
+```
+
+</details>
+
+<br>

packages/eslint-plugin-template/src/configs/all.json

@@ -24,6 +24,7 @@
     "@angular-eslint/template/no-interpolation-in-attributes": "error",
     "@angular-eslint/template/no-negated-async": "error",
     "@angular-eslint/template/no-positive-tabindex": "error",
+    "@angular-eslint/template/prefer-self-closing-tags": "error",
     "@angular-eslint/template/role-has-required-aria": "error",
     "@angular-eslint/template/table-scope": "error",
     "@angular-eslint/template/use-track-by-function": "error",

packages/eslint-plugin-template/src/index.ts

@@ -61,6 +61,9 @@ import noNegatedAsync, {
 import noPositiveTabindex, {
   RULE_NAME as noPositiveTabindexRuleName,
 } from './rules/no-positive-tabindex';
+import preferSelfClosingTags, {
+  RULE_NAME as preferSelfClosingTagsRuleName,
+} from './rules/prefer-self-closing-tags';
 import roleHasRequiredAria, {
   RULE_NAME as roleHasRequiredAriaRuleName,
 } from './rules/role-has-required-aria';
@@ -103,6 +106,7 @@ export = {
     [noInterpolationInAttributesRuleName]: noInterpolationInAttributes,
     [noNegatedAsyncRuleName]: noNegatedAsync,
     [noPositiveTabindexRuleName]: noPositiveTabindex,
+    [preferSelfClosingTagsRuleName]: preferSelfClosingTags,
     [roleHasRequiredAriaRuleName]: roleHasRequiredAria,
     [tableScopeRuleName]: tableScope,
     [useTrackByFunctionRuleName]: useTrackByFunction,

packages/eslint-plugin-template/src/rules/prefer-self-closing-tags.ts

@@ -0,0 +1,76 @@
+import type {
+  TmplAstElement,
+  TmplAstText,
+} from '@angular-eslint/bundled-angular-compiler';
+import { getTemplateParserServices } from '@angular-eslint/utils';
+import { createESLintRule } from '../utils/create-eslint-rule';
+import { getDomElements } from '../utils/get-dom-elements';
+
+export const MESSAGE_ID = 'preferSelfClosingTags';
+export const RULE_NAME = 'prefer-self-closing-tags';
+
+export default createESLintRule<[], typeof MESSAGE_ID>({
+  name: RULE_NAME,
+  meta: {
+    type: 'layout',
+    docs: {
+      description:
+        'Ensures that self-closing tags are used for elements with a closing tag but no content.',
+      recommended: false,
+    },
+    fixable: 'code',
+    schema: [],
+    messages: {
+      [MESSAGE_ID]:
+        'Use self-closing tags for elements with a closing tag but no content.',
+    },
+  },
+  defaultOptions: [],
+  create(context) {
+    const parserServices = getTemplateParserServices(context);
+
+    return {
+      Element$1({
+        children,
+        name,
+        startSourceSpan,
+        endSourceSpan,
+      }: TmplAstElement) {
+        // Ignore native elements.
+        if (getDomElements().has(name)) {
+          return;
+        }
+
+        const noContent =
+          !children.length ||
+          children.every((node) => {
+            const text = (node as TmplAstText).value;
+
+            // If the node has no value, or only whitespace,
+            // we can consider it empty.
+            return (
+              typeof text === 'string' && text.replace(/\n/g, '').trim() === ''
+            );
+          });
+        const noCloseTag =
+          !endSourceSpan ||
+          (startSourceSpan.start.offset === endSourceSpan.start.offset &&
+            startSourceSpan.end.offset === endSourceSpan.end.offset);
+
+        if (!noContent || noCloseTag) {
+          return;
+        }
+
+        context.report({
+          loc: parserServices.convertNodeSourceSpanToLoc(endSourceSpan),
+          messageId: MESSAGE_ID,
+          fix: (fixer) =>
+            fixer.replaceTextRange(
+              [startSourceSpan.end.offset - 1, endSourceSpan.end.offset],
+              ' />',
+            ),
+        });
+      },
+    };
+  },
+});