Fail parsing on HTML syntax error

.gitignore

@@ -139,3 +139,6 @@ dist
 # Vite logs files
 vite.config.js.timestamp-*
 vite.config.ts.timestamp-*
+
+# IDE files
+.idea

package.json

@@ -42,5 +42,8 @@
   },
   "peerDependencies": {
     "prettier": "^3.0.0"
+  },
+  "dependencies": {
+    "angular-html-parser": "^10.6.1"
   }
 }

src/parser.ts

@@ -10,6 +10,7 @@ import {
   Placeholder,
   RootNode,
 } from "./jte";
+import {parseHtml} from "angular-html-parser";
 
 const NOT_FOUND = -1;
 const IGNORE_START = /^<!--\s*prettier-ignore-start\s*-->/;
@@ -30,6 +31,28 @@ export const parse: Parser<Node>["parse"] = (text) => {
   const generatePlaceholder = placeholderGenerator(text);
   root.content = parseFragment(text, root.nodes, generatePlaceholder);
 
+  // Validate HTML using the same parser prettier uses internally
+  const { errors } = parseHtml(root.content, {
+    canSelfClose: true,
+    allowHtmComponentClosingTags: true,
+  });
+
+  if (errors.length > 0) {
+    const error = errors[0];
+    const { msg, span: { start, end } } = error;
+    const line = start.line + 1;
+    const col = start.col;
+
+    const err = new SyntaxError(
+        `${msg} (${line}:${col + 1})`
+    );
+    (err as any).loc = {
+      start: { line, column: col + 1 },
+      end: { line: end.line + 1, column: end.col },
+    };
+    throw err;
+  }
+
   return root;
 };
 

test/parser.test.ts

@@ -14,3 +14,13 @@ test("keeps broken directive text untouched", async () => {
       .content,
   ).toEqual("<div>@for(var entry : entries </div>");
 });
+test("throws on invalid HTML nesting", () => {
+  expect(() =>
+      parse("<p><ul><li>item</li></ul></p>", {} as ParserOptions)
+  ).toThrow(SyntaxError);
+});
+test("throws on malformed tag", () => {
+  expect(() =>
+      parse("<strong>Title</strong>\n</\n<ul><li>item</li></ul>", {} as ParserOptions)
+  ).toThrow(SyntaxError);
+});