Add mathml tag check

package.json

@@ -31,6 +31,7 @@
     "content-tag": "^2.0.1",
     "eslint-scope": "^7.2.2",
     "html-tags": "^3.3.1",
+    "mathml-tag-names": "^2.1.3",
     "svg-tags": "^1.0.0"
   },
   "devDependencies": {

src/parser/transforms.js

@@ -5,6 +5,7 @@ const { visitorKeys: glimmerVisitorKeys } = require('@glimmer/syntax');
 const { Reference, Scope, Variable, Definition } = require('eslint-scope');
 const htmlTags = require('html-tags');
 const svgTags = require('svg-tags');
+const mathMLTags = require('mathml-tag-names');
 
 let TypescriptScope = null;
 try {
@@ -489,7 +490,7 @@ module.exports.convertAst = function convertAst(result, preprocessedResult, visi
       if we do not find a variable we register it with a missing variable if
         * it starts with upper case, it should be a component with a reference
         * it includes a dot, it's a path which should have a reference
-        * it's NOT a standard html or svg tag, it should have a referenced variable
+        * it's NOT a standard html, svg or mathml tag, it should have a referenced variable
       */
       const ignore =
         // Local instance access
@@ -507,7 +508,9 @@ module.exports.convertAst = function convertAst(result, preprocessedResult, visi
       const registerUndef =
         isUpperCase(n.name[0]) ||
         node.name.includes('.') ||
-        (!htmlTags.includes(node.name) && !svgTags.includes(node.name));
+        (!htmlTags.includes(node.name) &&
+          !svgTags.includes(node.name) &&
+          !mathMLTags.includes(node.name));
 
       if (!ignore && (variable || registerUndef)) {
         registerNodeInScope(n, scope, variable);

tests/parser.test.js

@@ -2721,6 +2721,24 @@ export const NotFound = <template>
     expect(result.scopeManager.scopes[0].through.length).toBe(0);
   });
 
+  it('mathml elements are not added to global scope', () => {
+    result = parseForESLint(
+      `<template>
+        <math><msqrt><mi>x</mi></msqrt></math>
+        <mi>x</mi>
+      </template>`,
+      {
+        filePath: 'example.gts',
+        comment: true,
+        loc: true,
+        range: true,
+        tokens: true,
+      }
+    );
+
+    expect(result.scopeManager.scopes[0].through.length).toBe(0);
+  });
+
   it('custom-elements are ignored entirely, like they are in the browser', () => {
     result = parseForESLint(
       `<template>