cat: distinguish read and write errors by wtcpython · Pull Request #14721 · uutils/coreutils

wtcpython · 2026-09-19T11:17:41Z

Should make test cat/cat-distinct-err.sh pass

oech3 · 2026-09-19T11:49:23Z

+            PipeError::Read(error) | PipeError::Write(error) => error,
+        }
+    }
+}


This is currently unwrapping Read,Write for other utils. But we should distinct at all utils and remove this impl in the future. This is why we should https://github.com/uutils/coreutils/pull/14721/changes#r4053088325 .

This is fine for now.

github-actions · 2026-09-19T13:22:26Z

GNU testsuite comparison:

Congrats! The gnu test tests/cat/cat-distinct-err is no longer failing!

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oech3 · 2026-09-21T00:58:05Z

    #[error("{}", strip_errno(.0))]
    Io(#[from] io::Error),
+    #[error("{}: {}", translate!("common-write-error"), strip_errno(.0))]
+    Write(io::Error),


Can we directly put uucore::io::DistinguishedIOError::Write at here?

uucore::io::DistinguishedIOError does not yet exist, let's fix the test and refactor later.

codspeed · 2026-09-21T01:39:49Z

Merging this PR will regress 1 benchmark

⚠️

117 benchmarks spent significant time in system calls

System calls cannot be consistently instrumented, so they are not included in the measure, which understates the real cost. Please switch to the Walltime instrument to accurately measure system calls.

Measurement and system calls

cksum_multiple_files

dd_copy_partial

du_all_wide_tree[(5000, 500)]

cksum_raw_output

cksum_crc

cksum_default

du_wide_tree[(5000, 500)]

dd_copy_1m_blocks

cat_default[10000000]

check_sorted_utf8_locale

…and 107 more

ℹ️ 1 benchmark has no flame graph

The flamegraph could not be generated because too much time was spent in runtime internals, making the visualization not useful for performance analysis.

sort_dictionary_order[500000]

⚡ 1 improved benchmark
❌ 1 regressed benchmark
✅ 399 untouched benchmarks
⏩ 54 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	`BASE`	`HEAD`	Efficiency
❌	Simulation	`three_39_bit_primes`	591.3 ms	686 ms	-13.8%
⚡	Simulation	`five_38_bit_primes`	2.1 s	1.5 s	+34.85%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

_{Comparing wtcpython:cat-distinct-err (e5c769e) with main (01a8fc0)}

54 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

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Review effort: Lite
Findings: 2 · 1

Open (3)

PipeError is a public error type but only derives Debug; it doesn’t implement… · New
Mapping all drain_pipe I/O errors to PipeError::Write can misclassify failures coming from… · New
Asserting an exact OS-provided error string can be brittle across libc/locale/platform variations;… · New

+    Read(std::io::Error),
+    Write(std::io::Error),
+}
+


+            if drain_pipe(pipe_rd, dest, n)
+                .map_err(PipeError::Write)?
+                .is_err()
+            {


                .ignore_stdin_write_error()
                .fails()
-                .stderr_contains("No space left on device");
+                .stderr_is("cat: write error: No space left on device\n");


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sylvestre · 2026-10-08T20:46:08Z

        if let Err(err) = cat_path(path, options, &mut state) {
-            error_messages.push(format!("{}: {err}", path.maybe_quote()));
+            let is_write_error = matches!(&err, CatError::Write(_));
+            error_messages.push(match &err {


could be simpler, no? if let CatError::Write(_) = err { error_messages.push(err.to_string()); break; } and keep the old push otherwise

sylvestre · 2026-10-08T20:46:11Z

-                    .inspect_err(handle_broken_pipe)?;
+                    .inspect_err(handle_broken_pipe)
+                    .map_err(CatError::Write)?;
                // cannot use rustix::io on Windows


what about print_lines? cat -n - /dev/zero > /dev/full still goes through Io, so it gets the -: prefix and doesn't stop
please handle it too and add a test with -n

sylvestre · 2026-10-08T20:46:20Z

+}
+
 type PipeRes = std::io::Result<Result<(), ()>>;
+type SpliceRes = Result<Result<(), ()>, PipeError>;


the doc explaining the Ok(Ok)/Ok(Err)/Err meaning was removed, could you please keep it on SpliceRes?

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cakebaker · 2026-10-15T07:30:38Z

Congrats! The gnu test tests/cat/cat-distinct-err is no longer failing!

Great, thanks!

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Comment thread src/uucore/src/lib/features/pipes.rs

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Comment thread src/uucore/src/lib/features/pipes.rs

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sylvestre mentioned this pull request Sep 19, 2026

GNU coreutils 9.12: remaining test failures - Sept 2026 #14705

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cat: distinguish read and write errors

e5c769e

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cakebaker merged commit 59cd0b5 into uutils:main Oct 15, 2026
190 of 193 checks passed

wtcpython deleted the cat-distinct-err branch October 15, 2026 07:38

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Merging this PR will regress 1 benchmark

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