Parsing errors and content lost when saving Markdown #525

These examples show parsing errors and content lost when Comark saves Markdown. Reproduced on Comark 0.8.1 and main at b17f456.

Keep a case unchecked until its fix is merged and verified. Each linked PR is a proposed fix; cases without a fix link have no matching open PR found. Playground links use the preview from #526. Open the Formatted tab to see what changes when the Markdown is saved.

Markdown loses content when saved

References: GFM task lists and CommonMark fenced code blocks. Cases 2–4 concern Comark components.

• 1. Task items with nested blocks lose their text and indent following blocks as code. playground · Fix: #527 (open)
• 2. ::table{src="data.csv"} is saved as an empty table. playground · Fix: #527 (open)
• 3. :comment[a note] disappears. playground · Fix: #527 (open)
• 4. :math[x] becomes $x$ instead of staying a component. playground · Fix: #527 (open)
• 5. Fenced code loses trailing blank lines and spaces. playground · Fix: #527 (open)

Text moves out of HTML tags

Also reported in #505. Reference: CommonMark raw HTML.

• 6. Raw <details> inside ::tabs-item loses its nesting and content. Also tracked in Inline HTML inside a block component loses its content (0.8) #505. playground · Fix: #506 (open)
• 7. Text moves outside its HTML tag when that tag is inside emphasis, a link, or a heading. playground · Fix: #506 (open)

HTML parsing

References: CommonMark raw HTML, HTML blocks, soft line breaks, and browser HTML tree construction. For malformed HTML, the expected output follows how browsers parse it.

• 8. Newlines inside HTML disappear, joining words and script lines. playground
• 9. An HTML block with JSX-style attributes, such as <div style={{a: 1}}>, becomes literal text instead of remaining HTML. playground · Fix: #530 (open)
• 10. An HTML tag left open inside a paragraph swallows later blocks. playground · Fix: #530 (open)
• 11. </br> disappears instead of producing the line break browsers give it. playground · Fix: #530 (open)
• 12. A second <p> nests inside the first instead of closing it. playground · Fix: #530 (open)
• 13. Images, <br>, and custom elements inside HTML split or lose their paragraph. playground · Fix: #530 (open)
• 14. An HTML tag left open in a list changes the text order and adds a <fragment> element. playground · Fix: #530 (open)
• 15. Standalone HTML comments gain a <p> wrapper. Comark also fails to recognize <!--- ---> as a comment. playground · Fix: #530 (open)
• 16. Raw <pre><code> content renders its tags and entities literally. playground · Fix: #530 (open)
• 17. autoUnwrap removes a <p> written by the author and moves its attributes onto the parent. playground · Fix: #530 (open)
• 18. Duplicate HTML attributes keep the last value rather than the first. playground · Fix: #530 (open)
• 19. html({ markdown: false }) leaves character references encoded in HTML text. · Fix: #530 (open)

Markdown structure and autolinks

References: CommonMark images, ATX headings, fenced code blocks, block quotes, list items, GFM tables, and GFM autolinks.

• 20. Decorative Markdown images lose alt="". playground
• 21. Empty ATX headings disappear. playground
• 22. A code block's language disappears when it is written as {x}. playground
• 23. Bare URLs and emails differ from GFM for .dev addresses, underscores in hosts, non-numeric ports, emphasis around URLs, and percent-encoded link text. playground · example 2 · example 3 · example 4
• 24. markdown-exit parses some indented blockquote lines, code fences inside lists, and table rows inside list items differently from the spec. playground · example 2 · example 3

Comark attributes and frontmatter

CommonMark does not define these Comark extensions: attributes and frontmatter.

• 25. An unclosed attribute group, such as a {b c, deletes the rest of the line. playground
• 26. --- x closes frontmatter too early. A leading byte order mark stops Comark from finding frontmatter. playground · example 2
• 27. Invalid YAML frontmatter makes parseMarkdown throw. Report the invalid YAML without losing the document. playground

Callouts and footnotes

CommonMark does not define these extensions. References: GitHub alerts and Comark footnotes.

• 28. > [!NOTE] Title moves Title into the body when saved. fix(stringify): fix renderMarkdown round-trip losses from #525 #527 leaves this out because the parser and renderers need to agree on how to store the title. playground
• 29. Footnote definitions do not parse Markdown. The plugin also deletes definition-like lines inside code blocks and uses the last duplicate definition. playground · example 2 · example 3

Code changes when rendered, and large paragraphs crash

Reference: CommonMark fenced code blocks. Cases 30 and 31 need the API reproductions below.

• 30. @comark/html adds indentation inside nested code and escapes > in <style>/<script>, changing their content.
• 31. A paragraph with many children throws RangeError: parseMarkdown("https://x.com/a ".repeat(65536)).

Examples that need the API

import { parseMarkdown } from "comark";
import { renderHtmlFromDocument } from "@comark/html";
import html from "comark/plugins/html";

// 30: Code indentation changes, and the CSS selector becomes a > b.
console.log(await renderHtmlFromDocument(await parseMarkdown(
  "- x\n\n  ```\n  a\n    b\n  ```\n\n<style>\na > b {}\n</style>"
)));

// 19: Expected HTML text is "<b> & x", not "&lt;b&gt; &amp; x".
console.log((await parseMarkdown("<div>\n&lt;b&gt; &amp; x\n</div>", {
  plugins: [html({ markdown: false })]
})).nodes);

// 31: RangeError: Maximum call stack size exceeded.
await parseMarkdown("https://x.com/a ".repeat(65536));

Runnable checks for all cases.