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fix: Handle case-insensitive www. prefix #3769

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fix: Handle case-insensitive www. prefix #3769

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2 changes: 1 addition & 1 deletion src/Tokenizer.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -840,7 +840,7 @@ export class _Tokenizer<ParserOutput = string, RendererOutput = string> {
cap[0] = this.rules.inline._backpedal.exec(cap[0])?.[0] ?? '';
} while (prevCapZero !== cap[0]);
text = cap[0];
if (cap[1] === 'www.') {
if (cap[1]?.toLowerCase() === 'www.') {

@gemini-code-assist gemini-code-assist Bot Sep 26, 2025

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medium

This change correctly handles case-insensitive www. prefixes. However, the generated href preserves the original casing of the domain (e.g., http://Www.foo.com).

According to RFC 3986, the host component of a URI is case-insensitive. It is a best practice to normalize it to lowercase in the href attribute for consistency and to prevent potential issues. The visible link text should preserve the original user input.

You could consider updating the logic inside this if block to normalize the domain part of the URL. Here's a possible implementation:

// inside the if (cap[1]?.toLowerCase() === 'www.') block
const pathStartIndex = cap[0].search(/[\/?#]/);
const domain = pathStartIndex === -1 ? cap[0] : cap[0].substring(0, pathStartIndex);
const path = pathStartIndex === -1 ? '' : cap[0].substring(pathStartIndex);
href = 'http://' + domain.toLowerCase() + path;

If you apply this change, please remember to update the corresponding test case in test/specs/new/autolinks.html to expect a lowercase href.

href = 'http://' + cap[0];
} else {
href = cap[0];
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6 changes: 5 additions & 1 deletion test/specs/new/autolinks.html
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Expand Up @@ -8,8 +8,12 @@

<p><a href="hTtP://fOo.CoM">hTtP://fOo.CoM</a></p>

<p><a href="http://www.foo.com">www.foo.com</a></p>

<p><a href="http://Www.foo.com">Www.foo.com</a></p>

<p><del><a href="mailto:hello@email.com">hello@email.com</a></del></p>

<p><strong><a href="mailto:me@example.com">me@example.com</a></strong></p>

<p><strong><a href="mailto:test@test.com">test@test.com</a></strong></p>
<p><strong><a href="mailto:test@test.com">test@test.com</a></strong></p>
6 changes: 5 additions & 1 deletion test/specs/new/autolinks.md
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Expand Up @@ -8,8 +8,12 @@ HTTP://FOO.COM

hTtP://fOo.CoM

www.foo.com

Www.foo.com

~~hello@email.com~~

**me@example.com**

__test@test.com__
__test@test.com__