fix(mdxish): tone down empty line addition preprocessing after html blocks by eaglethrost · Pull Request #1344 · readmeio/markdown

eaglethrost · 2026-02-16T03:53:44Z

	Fix RM-15306

🧰 Changes

Tightens up the preprocessing logic in mdxish to add blank lines after HTML construct lines introduced in #1336 to no longer do so if the next line is an HTML construct or not indented.

The previous logic was causing a regression where the new blank line caused an HTML line after an opening HTML tag, that was 4 tabs indented, to get rendered as a code block instead of an html element. In common mark, lines with at least 4 indents are treated as code blocks (see here), but if it's right under a line with an HTML construct (opened or closed), it won't get treated as a code block. Hence the additional blank line caused the customer HTML to break.

The adjusted conditions here removes adding blank lines where we don't want it to be added, and also where it's not really needed (if the next line is indented as it already doesn't get consumed by the previous line HTML flow)

🧬 QA & Testing

In the markdown playground, test these markdown with mdxish flag on:

<div>
        <a class="glossary-letter" href="#a">A</a> |
        <a class="glossary-letter" href="#b">B</a> |
</div>

<div>
[block:callout]
{
  "type": "success",
  "body": "Hello"
}
[/block]
</div>

The indented HTML tags wrapped in an HTML tree shouldn't get converted to code block, and any content right after a line with HTML construct should get rendered & not consumed (retain that behaviour)
Test with more examples & compare it with legacy, basically there shouldn't be any difference

maximilianfalco · 2026-02-16T04:02:59Z

__tests__/transformers/terminate-html-flow-blocks.test.ts

+[/block]
+</div>
+      `);
+    })


Suggested change

})

});

maximilianfalco · 2026-02-16T04:03:32Z

__tests__/transformers/terminate-html-flow-blocks.test.ts

 \`\`\``);
-  });
+    });
+  })


Suggested change

})

});

maximilianfalco · 2026-02-16T04:04:04Z

__tests__/transformers/terminate-html-flow-blocks.test.ts


-  it('does not catastrophically backtrack on malformed tags with spaces', () => {
-    const input = `<a${' '.repeat(1000)}`;
+    it('does not add a blank line after an opening that that already has a blank line after it', () => {


Suggested change

it('does not add a blank line after an opening that that already has a blank line after it', () => {

it('does not add a blank line after an opening tag that already has a blank line after it', () => {

maximilianfalco · 2026-02-16T04:13:11Z

processor/transform/mdxish/terminate-html-flow-blocks.ts

-      (STANDALONE_HTML_LINE_REGEX.test(lines[i]) || HTML_LINE_WITH_CONTENT_REGEX.test(lines[i])) &&
-      lines[i + 1].trim().length > 0
-    ) {
+    if (i >= lines.length - 1 || lines[i + 1].trim().length === 0 || lines[i + 1].startsWith(' ')) {


Suggested change

if (i >= lines.length - 1 || lines[i + 1].trim().length === 0 || lines[i + 1].startsWith(' ')) {

if (i >= lines.length - 1 || lines[i + 1].trim().length === 0 || lines[i + 1].startsWith(' ') || lines[i + 1].startsWith('\t')) {

can you add this as well, it looks like we are only considering when spaces start the next line but would be great to cover for \t cases as well

you can use this test case, the top one uses \t and the bottom uses spaces

<div> <a class="glossary-letter" href="#a">A</a> | <a class="glossary-letter" href="#b">B</a> | </div> --- <div> <a class="glossary-letter" href="#a">A</a> | <a class="glossary-letter" href="#b">B</a> | </div>

currently is broken on \t

Really good catch thanks!

maximilianfalco

lgtm!

maximilianfalco

derefering to kevin and rafe for final approval!

davinhazard · 2026-02-17T22:28:22Z

processor/transform/mdxish/terminate-html-flow-blocks.ts

+      continue;
+    }
+
+    const isCurrentLineHtml = STANDALONE_HTML_LINE_REGEX.test(lines[i]) || HTML_LINE_WITH_CONTENT_REGEX.test(lines[i]);


small nit (not blocking): these could be DRY'ed up a bit with a small util isLineHtml that accepts the line and runs both the conditionals

davinhazard · 2026-02-17T22:29:03Z

processor/transform/mdxish/terminate-html-flow-blocks.ts

-      (STANDALONE_HTML_LINE_REGEX.test(lines[i]) || HTML_LINE_WITH_CONTENT_REGEX.test(lines[i])) &&
-      lines[i + 1].trim().length > 0
-    ) {
+    if (i >= lines.length - 1 || lines[i + 1].trim().length === 0 || lines[i + 1].startsWith(' ') || lines[i + 1].startsWith('\t')) {


nit: i find a comment helpful when there are lots of conditionals to resolve in an if statement!

## Version 13.2.0 ### ✨ New & Improved * **demo:** add a markdown view in demo app when stripComments is on ([#1348](#1348)) ([a7a8726](a7a8726)) * extend regex to cover more cases ([#1338](#1338)) ([3e8efc8](3e8efc8)) ### 🛠 Fixes & Updates * **mdxish:** add missing toMarkdown extension for MDX expressions in stripComments ([#1347](#1347)) ([02ddfce](02ddfce)) * properly escape escaped chars when expression parsing fails ([#1325](#1325)) ([136f7af](136f7af)) * **mdxish:** tone down empty line addition preprocessing after html blocks ([#1344](#1344)) ([e4e7362](e4e7362)), closes [#1336](#1336)

rafegoldberg · 2026-02-18T19:55:38Z

This PR was released!

🚀 Changes included in v13.2.0

eaglethrost added 3 commits February 16, 2026 12:57

style: reorganize terminate html flow tests

eade1f7

fix: only apply line for non indented non-html lines

95f9452

test: rendering test & jsx test

5e9b685

eaglethrost requested a review from maximilianfalco February 16, 2026 03:53

maximilianfalco reviewed Feb 16, 2026

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__tests__/transformers/terminate-html-flow-blocks.test.ts Outdated

[/block]

</div>

`);

})

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Suggested change

})

});

maximilianfalco reviewed Feb 16, 2026

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__tests__/transformers/terminate-html-flow-blocks.test.ts Outdated

\`\`\``);

});

});

})

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})

});

maximilianfalco reviewed Feb 16, 2026

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maximilianfalco requested changes Feb 16, 2026

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eaglethrost added 2 commits February 16, 2026 15:14

fix: format

e9125db

fix: deal with \t

fc84245

eaglethrost requested a review from maximilianfalco February 16, 2026 04:23

maximilianfalco reviewed Feb 16, 2026

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maximilianfalco approved these changes Feb 16, 2026

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eaglethrost requested review from kevinports and rafegoldberg February 16, 2026 09:21

kevinports approved these changes Feb 17, 2026

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davinhazard reviewed Feb 17, 2026

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eaglethrost added 4 commits February 18, 2026 12:12

Merge branch 'next' into dimas/RM-15306-html-treated-as-code-blocks-fix

885ef5c

style: comment

8719a74

test: add unindented case

b12ea7e

fix: dry

dfa7fe9

eaglethrost merged commit e4e7362 into next Feb 18, 2026
11 checks passed

eaglethrost deleted the dimas/RM-15306-html-treated-as-code-blocks-fix branch February 18, 2026 13:16

rafegoldberg added the released label Feb 18, 2026

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fix(mdxish): tone down empty line addition preprocessing after html blocks#1344

fix(mdxish): tone down empty line addition preprocessing after html blocks#1344
eaglethrost merged 9 commits intonextfrom
dimas/RM-15306-html-treated-as-code-blocks-fix

eaglethrost commented Feb 16, 2026

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	it('does not add a blank line after an opening that that already has a blank line after it', () => {
	it('does not add a blank line after an opening tag that already has a blank line after it', () => {

	if (i >= lines.length - 1 \|\| lines[i + 1].trim().length === 0 \|\| lines[i + 1].startsWith(' ')) {
	if (i >= lines.length - 1 \|\| lines[i + 1].trim().length === 0 \|\| lines[i + 1].startsWith(' ') \|\| lines[i + 1].startsWith('\t')) {

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eaglethrost commented Feb 16, 2026

🧰 Changes

🧬 QA & Testing

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rafegoldberg commented Feb 18, 2026

This PR was released!

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