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Bypass blob URL partitioning for top-level self fetches #1879

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Bypass blob URL partitioning for top-level self fetches #1879

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Bypass blob URL partitioning for top-level self fetches
recvfrom Nov 14, 2025
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recvfrom Nov 19, 2025
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recvfrom Nov 19, 2025
c35c3dd
Define `stringOrEnvironment` more broadly
recvfrom Nov 25, 2025
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37 changes: 32 additions & 5 deletions fetch.bs
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Expand Up @@ -5363,14 +5363,41 @@ returning a response directly, or allowing the request to proceed by returning n
<li><p>Let <var>isTopLevelNavigation</var> be true if <var>request</var>'s
<a for=request>destination</a> is "<code>document</code>"; otherwise, false.

<li><p>If <var>isTopLevelNavigation</var> is false and <var>requestEnvironment</var> is null,
then return a <a>network error</a>.
<li><p>Let <var>isTopLevelSelfFetch</var> be false.

<li><p>If <var>request</var>'s <a for=request>client</a> is non-null:
<ol>
<li><p>Let <var>global</var> be <var>request</var>'s <a for=request>client</a>'s
<a for="environment settings object">global object</a>.

<li>
<p>If all of the following conditions are true:

<ul class=brief>
<li><p><var>global</var> is a {{Window}} object;

<li><p><var>global</var>'s <a for=Window>navigable</a> is not null;
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@annevk annevk Nov 18, 2025

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I wonder if there are cases where this would be null and you can get this far into a fetch. Hmm.

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@domfarolino domfarolino Nov 19, 2025 •
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Specifically where client is non-null but not associated with a Window object? Would worker fetches count here? Maybe even navigation requests themselves, with their reserved client machinery...

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@recvfrom recvfrom Nov 19, 2025

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I mirrored this off of the logic in https://fetch.spec.whatwg.org/#populate-request-from-client, but I'm not certain that the cases there are possible here as well...


<li><p>Let <var>navigationOrEnvironment</var> be the string "<code>navigation</code>" if
<var>isTopLevelNavigation</var> is true; otherwise, <var>requestEnvironment</var>.
<li><p><var>global</var>'s <a for=Window>navigable</a>'s <a for=navigable>parent</a>
is null; and

<li><p><var>requestEnvironment</var>'s <a for="environment">creation URL</a>
<a for=url>equals</a> <var>request</var>'s <a for=request>current URL</a>,
</ul>

<p>then set <var>isTopLevelSelfFetch</var> to false.

<li><p>Let <var>stringOrEnvironment</var> be <var>requestEnvironment</var>.

<li><p>If <var>isTopLevelNavigation</var> is true, then set <var>stringOrEnvironment</var>
to the string "<code>navigation</code>".

<li><p>Otherwise, if <var>isTopLevelSelfFetch</var> is true, then set
<var>stringOrEnvironment</var> to the string "<code>top-level-self-fetch</code>".
</ol>

<li><p>Let <var>blob</var> be the result of <a>obtaining a blob object</a> given
<var>blobURLEntry</var> and <var>navigationOrEnvironment</var>.
<var>blobURLEntry</var> and <var>stringOrEnvironment</var>.

<li><p>If <var>blob</var> is not a {{Blob}} object, then return a <a>network error</a>.

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