fix: disable katex when allowMath is false in code block

mod.ts

@@ -15,6 +15,13 @@ Marked.marked.use(mangle());
 Marked.marked.use(gfmHeadingId());
 
 class Renderer extends Marked.Renderer {
+  allowMath: boolean;
+
+  constructor(options: Marked.marked.MarkedOptions & RenderOptions = {}) {
+    super(options);
+    this.allowMath = options.allowMath ?? false;
+  }
+
   heading(
     text: string,
     level: 1 | 2 | 3 | 4 | 5 | 6,
@@ -36,7 +43,7 @@ class Renderer extends Marked.Renderer {
 
     // transform math code blocks into HTML+MathML
     // https://github.blog/changelog/2022-06-28-fenced-block-syntax-for-mathematical-expressions/
-    if (language === "math") {
+    if (language === "math" && this.allowMath) {
       return katex.renderToString(code, { displayMode: true });
     }
     const grammar =
@@ -107,7 +114,7 @@ export function render(markdown: string, opts: RenderOptions = {}): string {
   const marked_opts = {
     baseUrl: opts.baseUrl,
     gfm: true,
-    renderer: new Renderer(),
+    renderer: new Renderer(opts),
   };
 
   const html = opts.inline

test/test.ts

@@ -30,6 +30,20 @@ Deno.test("Math rendering doesn't throw on invalid katex input", () => {
   render(" $&$");
 });
 
+Deno.test("When allowMath is not specified, make sure math is not rendered", () => {
+  const markdown = "This is a test $$y=x^2$$";
+  const expected = `<p>This is a test $$y=x^2$$</p>\n`;
+  const html = render(markdown);
+  assertEquals(html, expected);
+});
+
+Deno.test("When allowMath is not specified, make sure math code block is not rendered", () => {
+  const markdown = "```math\ny=x^2\n```";
+  const expected = `<pre><code>y=x^2</code></pre>`;
+  const html = render(markdown);
+  assertEquals(html, expected);
+});
+
 Deno.test("bug #61 generate a tag", () => {
   const markdown = "[link](https://example.com)";
   const expected =