render.mjs

Functions

Imports

It imports render-error.mjs, render-math.mjs, render-nomath.mjs. No module of this repo imports it.

Source

1// The markdown pipeline with math: render-nomath.mjs's pipeline, with remark-math, a KaTeX check of every expression and rehype-katex
2// passed in. KaTeX is imported only here, so a site that imports `render/nomath` never bundles it.
3
4import katex from "katex";
5import rehypeKatex from "rehype-katex";
6import remarkMath from "remark-math";
7import { visit } from "unist-util-visit";
8
9import { ContentError, errorMessage } from "./render-error.mjs";
10import { KATEX_OPTIONS } from "./render-math.mjs";
11import { renderWith } from "./render-nomath.mjs";
12
13export { ContentError, DEFAULT_MAX_BYTES, DEFAULT_MAX_DEPTH, RENDER_VERSION, isAllowedUrl } from "./render-nomath.mjs";
14
15/**
16 * The AST-side owner of hasMath; a site compares it with htmlHasMath over its corpus.
17 *
18 * @param {string} file
19 * @param {{ value: boolean }} sink set to true when the post carries any math
20 */
21function remarkMathValidate(file, sink) {
22  return (/** @type {import("mdast").Root} */ tree) => {
23    visit(tree, (node) => {
24      if (node.type !== "inlineMath" && node.type !== "math") return;
25      sink.value = true;
26
27      const expression = String(/** @type {any} */ (node).value ?? "");
28      const line = node.position?.start?.line;
29      try {
30        // The same KATEX_OPTIONS rehype-katex gets, so passing here proves its catch branch unreachable.
31        katex.renderToString(expression, {
32          ...KATEX_OPTIONS,
33          displayMode: node.type === "math",
34          throwOnError: true,
35        });
36      } catch (error) {
37        const detail = errorMessage(error);
38        // A line of the BODY: the tree is parsed without frontmatter, and an editor preview has no file.
39        throw new ContentError(
40          file,
41          `KaTeX cannot render ${node.type === "math" ? "the display" : "the inline"} ` +
42            `expression${line ? ` on line ${line} of the body` : ""}: ${detail}. ` +
43            `The expression is: ${expression.trim()}`,
44        );
45      }
46    });
47  };
48}
49
50/**
51 * Markdown in, a safe HTML fragment out, with `$…$` and `$$…$$` as math.
52 *
53 * @param {import("./render-nomath.mjs").RenderInput} input
54 */
55export function render(input) {
56  // Option 3 in render-nomath.mjs's header: KATEX_OPTIONS leaves `trust` off.
57  return renderWith(input, { parse: remarkMath, validate: remarkMathValidate, html: rehypeKatex, options: KATEX_OPTIONS });
58}