fix(compiler): incorrectly inferring namespace for HTML nodes inside SVG (#38477)

The HTML parser gets an element's namespace either from the tag name
(e.g. `<svg:rect>`) or from its parent element `<svg><rect></svg>`) which
breaks down when an element is inside of an SVG `foreignElement`,
because foreign elements allow nodes from a different namespace to be
inserted into an SVG.

These changes add another flag to the tag definitions which tells child
nodes whether to try to inherit their namespaces from their parents.
It also adds a definition for `foreignObject` with the new flag,
allowing elements placed inside it to infer their namespaces instead.

Fixes #37218.

PR Close #38477

packages/compiler-cli/test/ngtsc/template_typecheck_spec.ts

@@ -2017,6 +2017,28 @@ export declare class AnimationEvent {
         expect(diags.length).toBe(0);
       });
 
+      it('should allow HTML elements without explicit namespace inside SVG foreignObject', () => {
+        env.write('test.ts', `
+        import {Component, NgModule} from '@angular/core';
+        @Component({
+          template: \`
+            <svg>
+              <foreignObject>
+                <div>Hello</div>
+              </foreignObject>
+            </svg>
+          \`,
+        })
+        export class FooCmp {}
+        @NgModule({
+          declarations: [FooCmp],
+        })
+        export class FooModule {}
+      `);
+        const diags = env.driveDiagnostics();
+        expect(diags.length).toBe(0);
+      });
+
       it('should check for unknown elements inside an SVG foreignObject', () => {
         env.write('test.ts', `
         import {Component, NgModule} from '@angular/core';
@@ -2042,6 +2064,33 @@ export declare class AnimationEvent {
 1. If 'foo' is an Angular component, then verify that it is part of this module.
 2. To allow any element add 'NO_ERRORS_SCHEMA' to the '@NgModule.schemas' of this component.`);
       });
+
+      it('should check for unknown elements without explicit namespace inside an SVG foreignObject',
+         () => {
+           env.write('test.ts', `
+        import {Component, NgModule} from '@angular/core';
+        @Component({
+          selector: 'blah',
+          template: \`
+            <svg>
+              <foreignObject>
+                <foo>Hello</foo>
+              </foreignObject>
+            </svg>
+          \`,
+        })
+        export class FooCmp {}
+        @NgModule({
+          declarations: [FooCmp],
+        })
+        export class FooModule {}
+      `);
+           const diags = env.driveDiagnostics();
+           expect(diags.length).toBe(1);
+           expect(diags[0].messageText).toBe(`'foo' is not a known element:
+1. If 'foo' is an Angular component, then verify that it is part of this module.
+2. To allow any element add 'NO_ERRORS_SCHEMA' to the '@NgModule.schemas' of this component.`);
+         });
     });
 
     // Test both sync and async compilations, see https://github.com/angular/angular/issues/32538

packages/compiler/src/ml_parser/html_tags.ts

@@ -17,6 +17,7 @@ export class HtmlTagDefinition implements TagDefinition {
   isVoid: boolean;
   ignoreFirstLf: boolean;
   canSelfClose: boolean = false;
+  preventNamespaceInheritance: boolean;
 
   constructor({
     closedByChildren,
@@ -24,14 +25,16 @@ export class HtmlTagDefinition implements TagDefinition {
     contentType = TagContentType.PARSABLE_DATA,
     closedByParent = false,
     isVoid = false,
-    ignoreFirstLf = false
+    ignoreFirstLf = false,
+    preventNamespaceInheritance = false
   }: {
     closedByChildren?: string[],
     closedByParent?: boolean,
     implicitNamespacePrefix?: string,
     contentType?: TagContentType,
     isVoid?: boolean,
-    ignoreFirstLf?: boolean
+    ignoreFirstLf?: boolean,
+    preventNamespaceInheritance?: boolean
   } = {}) {
     if (closedByChildren && closedByChildren.length > 0) {
       closedByChildren.forEach(tagName => this.closedByChildren[tagName] = true);
@@ -41,6 +44,7 @@ export class HtmlTagDefinition implements TagDefinition {
     this.implicitNamespacePrefix = implicitNamespacePrefix || null;
     this.contentType = contentType;
     this.ignoreFirstLf = ignoreFirstLf;
+    this.preventNamespaceInheritance = preventNamespaceInheritance;
   }
 
   isClosedByChild(name: string): boolean {
@@ -88,6 +92,17 @@ export function getHtmlTagDefinition(tagName: string): HtmlTagDefinition {
       'th': new HtmlTagDefinition({closedByChildren: ['td', 'th'], closedByParent: true}),
       'col': new HtmlTagDefinition({isVoid: true}),
       'svg': new HtmlTagDefinition({implicitNamespacePrefix: 'svg'}),
+      'foreignObject': new HtmlTagDefinition({
+        // Usually the implicit namespace here would be redundant since it will be inherited from
+        // the parent `svg`, but we have to do it for `foreignObject`, because the way the parser
+        // works is that the parent node of an end tag is its own start tag which means that
+        // the `preventNamespaceInheritance` on `foreignObject` would have it default to the
+        // implicit namespace which is `html`, unless specified otherwise.
+        implicitNamespacePrefix: 'svg',
+        // We want to prevent children of foreignObject from inheriting its namespace, because
+        // the point of the element is to allow nodes from other namespaces to be inserted.
+        preventNamespaceInheritance: true,
+      }),
       'math': new HtmlTagDefinition({implicitNamespacePrefix: 'math'}),
       'li': new HtmlTagDefinition({closedByChildren: ['li'], closedByParent: true}),
       'dt': new HtmlTagDefinition({closedByChildren: ['dt', 'dd']}),
@@ -111,5 +126,8 @@ export function getHtmlTagDefinition(tagName: string): HtmlTagDefinition {
           {contentType: TagContentType.ESCAPABLE_RAW_TEXT, ignoreFirstLf: true}),
     };
   }
-  return TAG_DEFINITIONS[tagName.toLowerCase()] || _DEFAULT_TAG_DEFINITION;
+  // We have to make both a case-sensitive and a case-insesitive lookup, because
+  // HTML tag names are case insensitive, whereas some SVG tags are case sensitive.
+  return TAG_DEFINITIONS[tagName] ?? TAG_DEFINITIONS[tagName.toLowerCase()] ??
+      _DEFAULT_TAG_DEFINITION;
 }

packages/compiler/src/ml_parser/parser.ts

@@ -10,7 +10,7 @@ import {ParseError, ParseSourceSpan} from '../parse_util';
 
 import * as html from './ast';
 import * as lex from './lexer';
-import {getNsPrefix, isNgContainer, mergeNsAndName, TagDefinition} from './tags';
+import {getNsPrefix, mergeNsAndName, splitNsName, TagDefinition} from './tags';
 
 export class TreeError extends ParseError {
   static create(elementName: string|null, span: ParseSourceSpan, msg: string): TreeError {
@@ -353,7 +353,11 @@ class _TreeBuilder {
     if (prefix === '') {
       prefix = this.getTagDefinition(localName).implicitNamespacePrefix || '';
       if (prefix === '' && parentElement != null) {
-        prefix = getNsPrefix(parentElement.name);
+        const parentTagName = splitNsName(parentElement.name)[1];
+        const parentTagDefinition = this.getTagDefinition(parentTagName);
+        if (!parentTagDefinition.preventNamespaceInheritance) {
+          prefix = getNsPrefix(parentElement.name);
+        }
       }
     }
 

packages/compiler/src/ml_parser/tags.ts

@@ -19,6 +19,7 @@ export interface TagDefinition {
   isVoid: boolean;
   ignoreFirstLf: boolean;
   canSelfClose: boolean;
+  preventNamespaceInheritance: boolean;
 
   isClosedByChild(name: string): boolean;
 }

packages/compiler/src/ml_parser/xml_tags.ts

@@ -20,6 +20,7 @@ export class XmlTagDefinition implements TagDefinition {
   isVoid: boolean = false;
   ignoreFirstLf: boolean = false;
   canSelfClose: boolean = true;
+  preventNamespaceInheritance: boolean = false;
 
   requireExtraParent(currentParent: string): boolean {
     return false;