Stream: git-wasmtime

Topic: wasmtime / PR #14135 Return is-directory when a directory...

Wasmtime GitHub notifications bot (Aug 13 2026 at 22:19):

SebTardif opened PR #14135 from SebTardif:fix/dir-read-is-directory to bytecodealliance:main:

Prior discussion: WebAssembly/wasi-libc#869 (@alexcrichton: fix this in Wasmtime instead of extra libc syscalls).

Why

read() on a directory must return EISDIR (POSIX). Wasmtime's Descriptor::file() mapped a directory to error-code::bad-descriptor. wasi-libc then had to stat/get_type just to remap EBADF. On wasip3, read-via-stream is a tuple import, so that host ? trapped instead of returning a guest error.

wasi:filesystem already documents is-directory as the EISDIR analog. Descriptor::dir() already returns not-directory for a file. This makes file() the dual.

Change

• Descriptor::file() returns IsDirectory for Dir.
• wasip3 read-via-stream: if the descriptor is not a file, return an empty stream and resolve the result future with that error (same shape as p3 TCP receive). Do not trap.
• wasip1 guests are unchanged (fd_read still EBADF; preview1 adapter still ERRNO_BADF).

Tests

• p2_file_read_write: read_via_stream on the preopen directory is is-directory.
• p3_filesystem_file_read_write: the result future is IsDirectory (blocking and non-blocking).

Red (unpatched host): p2 guest saw bad-descriptor (code 3). Green: is-directory (code 14).

References

• WebAssembly/wasi-libc#869
• WebAssembly/wasi-libc#865
• rust-lang/rust#160359
• uutils/coreutils#13625
• Descriptor::file as used today was introduced in #11406 (cf88a7c601, 2025-08-12)
  

Wasmtime GitHub notifications bot (Aug 13 2026 at 22:19):

SebTardif requested dicej for a review on PR #14135.

Wasmtime GitHub notifications bot (Aug 13 2026 at 22:19):

SebTardif requested wasmtime-core-reviewers for a review on PR #14135.

Wasmtime GitHub notifications bot (Aug 13 2026 at 22:19):

SebTardif requested wasmtime-wasi-reviewers for a review on PR #14135.

Wasmtime GitHub notifications bot (Aug 13 2026 at 22:21):

:thumbs_up: alexcrichton submitted PR review:

Thanks!

Wasmtime GitHub notifications bot (Aug 13 2026 at 22:21):

alexcrichton has enabled auto merge for PR #14135.

Wasmtime GitHub notifications bot (Aug 13 2026 at 22:37):

alexcrichton has disabled auto merge for PR #14135.

Wasmtime GitHub notifications bot (Aug 13 2026 at 22:37):

SebTardif updated PR #14135.

Wasmtime GitHub notifications bot (Aug 13 2026 at 23:57):

github-actions[bot] added the label wasi on PR #14135.

Wasmtime GitHub notifications bot (Aug 14 2026 at 13:52):

dicej added PR #14135 Return is-directory when a directory fd is used as a file to the merge queue.

Wasmtime GitHub notifications bot (Aug 14 2026 at 14:18):

:check: dicej merged PR #14135.

Wasmtime GitHub notifications bot (Aug 14 2026 at 14:18):

dicej removed PR #14135 Return is-directory when a directory fd is used as a file from the merge queue.

Last updated: Aug 30 2026 at 09:07 UTC