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Fix nested code fence parsing in lists #103

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dacharyc merged 2 commits into from
Aug 23, 2026
Merged

Fix nested code fence parsing in lists #103

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e4c9e1d
Fix nested code fence parsing in lists
nathan-contino Aug 18, 2026
edc0662
fix: match list-indented fence openers by captured indentation
dacharyc Aug 23, 2026
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19 changes: 14 additions & 5 deletions src/checks/observability/markdown-content-parity.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -332,12 +332,21 @@ function extractMarkdownText(markdown: string): string {
// on a run of >=N. Capture the opener so the close-side backreference
// matches; otherwise nested example fences (4-backtick outer, 3-backtick
// inner) get mis-paired and inner markers leak out as text.
//
// Fences inside list items are indented by the list marker width (e.g.
// Turndown indents them 4 spaces under "1. item"), so the opener may not
// sit at column 0. Capture the opener's indentation and require the closer
// at the same indent plus the 0-3 spaces of slack CommonMark allows, so a
// more deeply indented literal ``` inside the block can't close it early.
const codeBlocks: string[] = [];
text = text.replace(/^(`{3,})[^`\n]*\n([\s\S]*?)^\1`*\s*$/gm, (_match, _opener, content) => {
const idx = codeBlocks.length;
codeBlocks.push(content);
return `\x00BLOCK${idx}\x00`;
});
text = text.replace(
/^( *)(`{3,})[^`\n]*\n([\s\S]*?)^\1 {0,3}\2`*\s*$/gm,
(_match, _indent, _opener, content) => {
const idx = codeBlocks.length;
codeBlocks.push(content);
return `\x00BLOCK${idx}\x00`;
},
);

// Step 2: Protect inline code spans from subsequent stripping.
// Replace `...` with placeholders so link/emphasis regexes don't
Expand Down
85 changes: 85 additions & 0 deletions test/unit/checks/markdown-content-parity.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -2658,4 +2658,89 @@ This test guards against regressions that special-case any single backtick run l
const pageResults = result.details?.pageResults as Array<{ missingSegments: number }>;
expect(pageResults[0].missingSegments).toBe(0);
});

it('protects fenced code blocks indented inside list items', async () => {
// Turndown indents fenced code blocks by 4 spaces when they appear inside
// numbered list items. Without this fix, the code fence regex (which
// required backticks at column 0) failed to match, leaving the YAML list
// lines unprotected. The list-marker stripper then removed the leading
// "- " from lines like "- db_data:/var/lib/postgresql/data", so the HTML
// segment "- db_data:/var/lib/postgresql/data" had no match in the
// stripped markdown text.
const html = `<html><body><main>
<h1>Install with Docker</h1>
<p>Use the steps below to install FusionAuth using Docker Compose.</p>
<ol>
<li>
<p>Download the configuration files from the repository.</p>
<p>Full docker-compose.yml example:</p>
<pre><code class="language-yaml">services:
db:
image: postgres:16.0-bookworm
volumes:
<span class="token punctuation">-</span> db_data<span class="token punctuation">:</span>/var/lib/postgresql/data
fusionauth:
image: fusionauth/fusionauth-app:latest
volumes:
<span class="token punctuation">-</span> fusionauth_config<span class="token punctuation">:</span>/usr/local/fusionauth/config
<span class="token punctuation">-</span> \${FUSIONAUTH_LOCAL_KICKSTART_DIRECTORY}<span class="token punctuation">:</span>/usr/local/fusionauth/kickstart
volumes:
db_data<span class="token punctuation">:</span>
fusionauth_config<span class="token punctuation">:</span>
</code></pre>
</li>
<li>
<p>Start the services with docker compose up.</p>
<p>The first startup may take several minutes while images download.</p>
</li>
</ol>
</main></body></html>`;

const markdown = `# Install with Docker

Use the steps below to install FusionAuth using Docker Compose.

1. Download the configuration files from the repository.

Full docker-compose.yml example:

\`\`\`yaml
services:
db:
image: postgres:16.0-bookworm
volumes:
- db_data:/var/lib/postgresql/data
fusionauth:
image: fusionauth/fusionauth-app:latest
volumes:
- fusionauth_config:/usr/local/fusionauth/config
- \${FUSIONAUTH_LOCAL_KICKSTART_DIRECTORY}:/usr/local/fusionauth/kickstart
volumes:
db_data:
fusionauth_config:
\`\`\`

2. Start the services with docker compose up.

The first startup may take several minutes while images download.`;

const url = 'http://mcp-indented-fence.local/docs/docker';

server.use(
http.get(
url,
() =>
new HttpResponse(html, {
status: 200,
headers: { 'Content-Type': 'text/html' },
}),
),
);

const ctx = makeCtx([{ url, markdown, htmlBody: html }], 'mcp-indented-fence.local');
const result = await check.run(ctx);
expect(result.status).toBe('pass');
const pageResults = result.details?.pageResults as Array<{ missingSegments: number }>;
expect(pageResults[0].missingSegments).toBe(0);
});
});