fix(@angular/build): support valid self-closing MathML tags in HTML index file

Prior to this change, the Angular build process incorrectly flagged self-closing MathML tags (e.g., `<msqrt />`) as invalid HTML. This commit rectifies this issue by explicitly allowing self-closing syntax for MathML elements embedded within the HTML index file.

(cherry picked from commit c33629e)

Author: alan-agius4

packages/angular/build/src/utils/index-file/augment-index-html.ts

@@ -10,6 +10,7 @@ import { createHash } from 'node:crypto';
 import { extname } from 'node:path';
 import { loadEsmModule } from '../load-esm';
 import { htmlRewritingStream } from './html-rewriting-stream';
+import { VALID_SELF_CLOSING_TAGS } from './valid-self-closing-tags';
 
 export type LoadOutputFileFunctionType = (file: string) => Promise<string>;
 
@@ -49,47 +50,6 @@ export interface FileInfo {
   extension: string;
 }
 
-/** A list of valid self closing HTML elements */
-const VALID_SELF_CLOSING_TAGS = new Set([
-  'area',
-  'base',
-  'br',
-  'col',
-  'embed',
-  'hr',
-  'img',
-  'input',
-  'link',
-  'meta',
-  'param',
-  'source',
-  'track',
-  'wbr',
-  /** SVG tags */
-  'circle',
-  'ellipse',
-  'line',
-  'path',
-  'polygon',
-  'polyline',
-  'rect',
-  'text',
-  'tspan',
-  'linearGradient',
-  'radialGradient',
-  'stop',
-  'image',
-  'pattern',
-  'defs',
-  'g',
-  'marker',
-  'mask',
-  'style',
-  'symbol',
-  'use',
-  'view',
-]);
-
 /*
  * Helper function used by the IndexHtmlWebpackPlugin.
  * Can also be directly used by builder, e. g. in order to generate an index.html

packages/angular/build/src/utils/index-file/valid-self-closing-tags.ts

@@ -0,0 +1,59 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+/** A list of valid self closing HTML elements */
+export const VALID_SELF_CLOSING_TAGS = new Set([
+  'area',
+  'base',
+  'br',
+  'col',
+  'embed',
+  'hr',
+  'img',
+  'input',
+  'link',
+  'meta',
+  'param',
+  'source',
+  'track',
+  'wbr',
+  /** SVG tags */
+  'circle',
+  'ellipse',
+  'line',
+  'path',
+  'polygon',
+  'polyline',
+  'rect',
+  'text',
+  'tspan',
+  'linearGradient',
+  'radialGradient',
+  'stop',
+  'image',
+  'pattern',
+  'defs',
+  'g',
+  'marker',
+  'mask',
+  'style',
+  'symbol',
+  'use',
+  'view',
+  /** MathML tags */
+  'mspace',
+  'mphantom',
+  'mrow',
+  'mfrac',
+  'msqrt',
+  'mroot',
+  'mstyle',
+  'merror',
+  'mpadded',
+  'mtable',
+]);