fix: handle backticks in link text for emphasis processing by sajdakabir · Pull Request #3779 · markedjs/marked

sajdakabir · 2025-10-03T11:04:08Z

[PR] fix: handle backticks in link-like bracket text during emphasis parsing

Marked version: 16.3.0
Markdown flavor: CommonMark | GitHub Flavored Markdown

Description

Fixes Link backtick processing seems subtly broken #3777 by updating the blockSkip regex to correctly mask backticks inside link-like bracket text before emphasis processing.

Expectation

Bold/italic should close correctly even when the text includes bracketed segments that look like links and contain code spans:

**Really weird edge case: bold around what looks like it might be a link, but is actually a link-looking thing with a code specifier in. [Like `this](https://github.com)`. It's now impossible to close the bold**

Expected output:

<p><strong>Really weird edge case: bold around what looks like it might be a link, but is actually a link-looking thing with a code specifier in. [Like <code>this](https://github.com)</code>. It's now impossible to close the bold</strong></p>

Result (before fix)

Emphasis remained unclosed because backticks within the bracketed segment were not masked, interfering with strong/em parsing.

Technical summary

The blockSkip regex (used to mask links/code/HTML before emphasis) didn’t handle backticks inside the bracket text [...].
Updated pattern for link text to:
- Exclude backticks from the generic char class.
- Explicitly match inline code spans within brackets.
- Simplify escape handling with \\..

New blockSkip:

\[(?:[^\[\]\\`]|\\.|`[^`]*`)*?\]\((?:\\.|[^\\\(\)]|\((?:\\.|[^\\\(\)])*\))*\)|`[^`]*?`|<(?!)[^<>]*?>

Contributor

Tests: existing suite passes (1705 tests), including:
- angle_brackets (ensures < and > don’t break emphasis)
- link_tick_redos (guards against ReDOS)

Committer

In most cases, this should be a different person than the contributor.

CI is green (no forced merge required).
Squash and Merge PR following conventional commit guidelines.

vercel · 2025-10-03T11:04:13Z

@sajdakabir is attempting to deploy a commit to the MarkedJS Team on Vercel.

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gemini-code-assist · 2025-10-03T11:04:22Z

Summary of Changes

Hello @sajdakabir, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves a specific parsing bug in the Markdown renderer that caused emphasis (like bold or italic) to fail to close correctly when encountering bracketed text that looked like a link but contained inline code spans (backticks). The core of the fix involves updating a regular expression (blockSkip) responsible for identifying and skipping certain text blocks, ensuring that backticks within these link-like structures are properly masked, thereby allowing the emphasis parser to function as expected.

Highlights

Emphasis Parsing Fix: Corrects an issue where bold/italic emphasis failed to close properly when text included bracketed segments resembling links that contained code spans (backticks).
blockSkip Regex Update: The blockSkip regular expression in src/rules.ts has been modified to properly mask backticks within link-like bracket text before emphasis processing.
Improved Markdown Robustness: This change enhances the parser's ability to correctly render complex Markdown constructs, specifically preventing parsing errors in edge cases involving nested formatting.

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gemini-code-assist

Code Review

This pull request fixes an issue where backticks in link text were not handled correctly during emphasis processing. The change updates the blockSkip regular expression to correctly identify and mask code spans within link text. The fix is effective for the described problem. I've added a comment with suggestions to improve the consistency and robustness of the regular expression.

gemini-code-assist · 2025-10-03T11:06:26Z


 // sequences em should skip over [title](link), `code`, <html>
-const blockSkip = /\[[^\[\]]*?\]\((?:\\[\s\S]|[^\\\(\)]|\((?:\\[\s\S]|[^\\\(\)])*\))*\)|`[^`]*?`|<(?! )[^<>]*?>/g;
+const blockSkip = /\[(?:[^\[\]\\`]|\\.|`[^`]*`)*?\]\((?:\\.|[^\\\(\)]|\((?:\\.|[^\\\(\)])*\))*\)|`[^`]*?`|<(?! )[^<>]*?>/g;


This is a good fix for handling backticks in link text. However, I have a couple of suggestions regarding the new regex pattern.

Greedy vs. Non-greedy: The new pattern for code spans within link text is `[^`]*` (greedy), while the existing pattern for standalone code spans in blockSkip is `[^`]*?` (non-greedy). For consistency and to avoid potential subtle issues, it would be better to use the non-greedy version (*?) here as well.

Multi-backtick code spans: A more significant point is that this regex pattern (both for standalone code spans and within links) only correctly handles single-backtick code spans. It doesn't support multi-backtick code spans (e.g., code ). This is a pre-existing limitation, but it's being replicated in the new logic. An unmasked code span containing characters like * could interfere with emphasis parsing, leading to incorrect rendering.

For example, with **[``*text*``](url)**, blockSkip would fail to mask the link and code span correctly, exposing *text* to the emphasis parser.

While a full fix for multi-backtick spans might be out of scope for this PR, I'd recommend at least making the quantifier non-greedy for consistency. The suggestion below applies this change.

Suggested change

const blockSkip = /\[(?:[^\[\]\\`]|\\.|`[^`]*`)*?\]\((?:\\.|[^\\\(\)]|\((?:\\.|[^\\\(\)])*\))*\)|`[^`]*?`|<(?! )[^<>]*?>/g;

const blockSkip = /\B(?:[^\[\]\\`]|\\.|`[^`]*?`)*?\]\((?:\\.|[^\\\(\)]|\((?:\\.|[^\\\(\)])*\))*\)|`[^`]*?`|<(?! )[^<>]*?>/g;

UziTech

/\[(?:[^\[\]\\`]|\\.|`[^`]*?`)*?\]\((?:\\.|[^\\\(\)]|\((?:\\.|[^\\\(\)])*\))*\)|`[^`]*?`|<(?! )[^<>]*?>/g

Is vulnerable to ReDOS. You can check it by pasting it into https://makenowjust-labs.github.io/recheck/playground/

sajdakabir · 2025-10-05T08:52:31Z

@UziTech lmk if any changes are needed.

vercel · 2025-10-07T03:05:22Z

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UziTech

Can you remove the indentation changes?

…ix-blockskip-backtick-issue-3777

sajdakabir · 2025-10-07T09:34:19Z

@UziTech its done

Can you remove the indentation changes?

@UziTech its done

UziTech

Thanks 💯

styfle · 2025-10-08T13:05:30Z

@@ -0,0 +1,2 @@
+<p><strong>Really weird edge case: bold around what looks like it might be a link, but is actually a link-looking thing with a code specifier in. [Like <code>this](https://github.com)</code>. It&#39;s now impossible to close the bold</strong>.</p>
+<p><strong>Bold text with [unmatched `backtick](url) should close</strong>.</p>


@UziTech I noticed this doesn't match the commonmark output.

Are we okay with that?

link to dingus

@styfle thanks! I’ve updated the test — this should be resolved now.

I think @styfle was talking about the second paragraph. That is a different bug. Can we just remove the second paragraph from the test?

The first paragraph isn't actually testing this fix currently

@UziTech so should i remove the second paragraph?

ya and undo the last fix

@UziTech its done , let me know if any other changes are needed.

…abir/marked into fix-blockskip-backtick-issue-3777

UziTech · 2025-10-12T03:34:36Z

Looks like this was actually fixed in the latest version by #3785

fix: handle backticks in link text for emphasis processing

2e073a9

gemini-code-assist Bot reviewed Oct 3, 2025

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sajdakabir mentioned this pull request Oct 3, 2025

Link backtick processing seems subtly broken #3777

Closed

sajdakabir added 2 commits October 3, 2025 16:52

feat: test files

6842940

refc: accept reviewer suggestion

f246c14

UziTech requested changes Oct 5, 2025

View reviewed changes

fix: improve regex for block skipping in emphasis processing

4b5cd95

sajdakabir requested a review from UziTech October 5, 2025 08:50

vercel Bot deployed to Preview October 7, 2025 03:05 View deployment

UziTech requested changes Oct 7, 2025

View reviewed changes

sajdakabir added 3 commits October 7, 2025 14:31

chore: remove whitespace

b20cb9d

Merge branch 'master' of github.com-personal:sajdakabir/marked into f…

6b96546

…ix-blockskip-backtick-issue-3777

refc: remove indentations

35cc17b

sajdakabir requested a review from UziTech October 8, 2025 05:47

vercel Bot deployed to Preview October 8, 2025 06:32 View deployment

UziTech approved these changes Oct 8, 2025

View reviewed changes

UziTech requested review from calculuschild and styfle October 8, 2025 06:33

styfle reviewed Oct 8, 2025

View reviewed changes

sajdakabir added 2 commits October 8, 2025 21:04

fix: correct link formatting in bold codespan edge case tests

b2b29a5

Merge branch 'fix-blockskip-backtick-issue-3777' of github.com:sajdak…

f919bb5

…abir/marked into fix-blockskip-backtick-issue-3777

vercel Bot deployed to Preview October 9, 2025 19:22 View deployment

refc: undo the last fix and remove the second paragraph

4504904

vercel Bot deployed to Preview October 12, 2025 03:32 View deployment

UziTech closed this Oct 16, 2025

	const blockSkip = /\[(?:[^\[\]\\`]\|\\.\|`[^`]`)?\]\((?:\\.\|[^\\\(\)]\|\((?:\\.\|[^\\\(\)])\))\)\|`[^`]?`\|<(?! )[^<>]?>/g;
	const blockSkip = /\B(?:[^\[\]\\`]\|\\.\|`[^`]?`)?\]\((?:\\.\|[^\\\(\)]\|\((?:\\.\|[^\\\(\)])\))\)\|`[^`]?`\|<(?! )[^<>]?>/g;

		@@ -0,0 +1,2 @@
		<p><strong>Really weird edge case: bold around what looks like it might be a link, but is actually a link-looking thing with a code specifier in. [Like <code>this](https://github.com)</code>. It's now impossible to close the bold</strong>.</p>
		<p><strong>Bold text with [unmatched `backtick](url) should close</strong>.</p> No newline at end of file

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sajdakabir commented Oct 3, 2025

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