os: missing conversion of internal/poll.ErrFileClosing to fs.ErrClosed

[nolta]

TL;DR: Posted to go-nuts, and Ian Lance Taylor responded:

I think this is a bug. (*File).readFrom, or perhaps NewSyscallError,
should convert poll.ErrFileClosing to os.ErrClosed, just as
(*File).wrapErr does.

I believe they're referring to this line in os/readfrom_linux.go.

What version of Go are you using (go version)?

$ go version
go version go1.18.10 linux/amd64

Does this issue reproduce with the latest release?

Don't know.

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/runner/.cache/go-build"
GOENV="/home/runner/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/runner/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/runner/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/opt/hostedtoolcache/go/1.18.10/x64"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/opt/hostedtoolcache/go/1.18.10/x64/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.18.10"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/runner/work/gosh/gosh/go.mod"
GOWORK=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build918714692=/tmp/go-build -gno-record-gcc-switches"

What did you do?

My code is essentially running shell pipelines, and i want to catch harmless errors where a process on the left side of the pipeline dies because the right side has finished. Think { echo 1; echo 2; echo 3; } | head -n1.

So in addition to catching EPIPEs and SIGPIPEs, i catch file closed errors:

// ignore writes to closed pipe
switch err := err.(type) {
case *fs.PathError:
    if err.Op == "write" && err.Path == "|1" && errors.Is(err.Err, fs.ErrClosed) {
        return nil
    }
}
return err

What did you expect to see?

Nothing.

What did you see instead?

Code dies with the error message write |1: copy_file_range: use of closed file. Since this error appears to be internal/poll.ErrFileClosing, i can't catch it since i can't import the package.

[thanm]

@golang/runtime

[gopherbot]

Change https://go.dev/cl/469795 mentions this issue: os: use errors.Is instead of equality operator to determine poll.ErrFileClosing in File.wrapErr