fix(ext/fetch): include path and reason when fetching a file:// URL fails#35606
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…ails Fetching a file:// URL that could not be opened always surfaced the opaque "NetworkError when attempting to fetch resource", discarding the underlying filesystem error. This was especially confusing for compiled binaries and `deno desktop` apps, where `fetch(import.meta.resolve(...))` on an asset that was not embedded with `--include` resolves to a path inside the compile VFS and fails with no indication that the file is simply missing. Preserve the real error and the URL instead, so the message becomes e.g. "Error fetching file 'file:///.../index.html': No such file or directory (os error 2)".
crowlKats
approved these changes
Jun 30, 2026
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Fetching a
file://URL that could not be opened always surfaced theopaque
NetworkError when attempting to fetch resource, discarding theunderlying filesystem error. The real reason (and which file) was lost
because
fs.open_asyncerrors were mapped withmap_err(|_| NetworkError).This is especially confusing for compiled binaries and
deno desktopapps. There,
fetch(import.meta.resolve("./index.html"))on an assetthat was not embedded with
--includeresolves to a path inside thecompile VFS and fails with no hint that the file is simply missing, as
reported in #35487.
This preserves the underlying error and the URL, so the message now
reads, for example:
The error remains a
TypeError(file fetches are a Deno extension, andkeeping the class matches the previous behavior and fetch semantics for
network errors). The path under the compile temp directory now also
serves as a strong hint that
--includeis needed.Fixes #35487.