wasm: reading from stdin fails with Windows

[evanw]

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

$ go version
go version go1.15.7 windows/amd64

Does this issue reproduce with the latest release?

Yes

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

go env Output

$ go env
set GO111MODULE=
set GOARCH=wasm
set GOBIN=
set GOCACHE=C:\Users\User\AppData\Local\go-build
set GOENV=C:\Users\User\AppData\Roaming\go\env
set GOEXE=
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOINSECURE=
set GOMODCACHE=C:\Users\User\go\pkg\mod
set GONOPROXY=
set GONOSUMDB=
set GOOS=js
set GOPATH=C:\Users\User\go
set GOPRIVATE=
set GOPROXY=https://proxy.golang.org,direct
set GOROOT=c:\go
set GOSUMDB=sum.golang.org
set GOTMPDIR=
set GOTOOLDIR=c:\go\pkg\tool\windows_amd64
set GCCGO=gccgo
set GOWASM=
set AR=ar
set CC=gcc
set CXX=g++
set CGO_ENABLED=0
set GOMOD=
set CGO_CFLAGS=-g -O2
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-g -O2
set CGO_FFLAGS=-g -O2
set CGO_LDFLAGS=-g -O2
set PKG_CONFIG=pkg-config
set GOGCCFLAGS=-fPIC -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=C:\Users\User\AppData\Local\Temp\go-build540642258=/tmp/go-build -gno-record-gcc-switches

What did you do?

Code:

package main

import "fmt"
import "io/ioutil"
import "os"

func main() {
	bytes, err := ioutil.ReadAll(os.Stdin)
	if err != nil {
		fmt.Printf("err is %q\n", err.Error())
	} else {
		fmt.Printf("stdin is %q\n", string(bytes))
	}
}

Build with:

C:\Users\User\Desktop>set GOROOT=js
C:\Users\User\Desktop>set GOARCH=wasm
C:\Users\User\Desktop>go build -o main.wasm main.go

What did you expect to see?

C:\Users\User\Desktop>echo abc | node c:\go\misc\wasm\wasm_exec.js main.wasm
stdin is "abc \r\n"

What did you see instead?

C:\Users\User\Desktop>echo abc | node c:\go\misc\wasm\wasm_exec.js main.wasm
panic: <object>

goroutine 6 [running]:
syscall.mapJSError(0x7ff8000100000015, 0x418128, 0x160f0008, 0x7ff8000100000011)
        c:/go/src/syscall/fs_js.go:552 +0x1e
syscall.fsCall.func1(0x0, 0x0, 0x432240, 0x3, 0x3, 0x418120, 0x40000430700)
        c:/go/src/syscall/fs_js.go:507 +0xb
syscall/js.handleEvent()
        c:/go/src/syscall/js/func.go:96 +0x24

This is due to a bug in node where fs.read behaves incorrectly on Windows. It returns an EOF error when it hits the end of the file (the <object> is the EOF error object). There are at least two reports including https://github.com/nodejs/node/issues/35997 and https://github.com/nodejs/node/issues/19831.

However, I'm reporting it here because a) this bug is really old so it's all over the place in the wild and b) I think it's easy for Go to work around. My suggested workaround is to treat an EOF error from fs.read as null which should both avoid the panic and match Go's behavior on Unix.

[codefromthecrypt]

I ran into this in a different case. the root issue is that the parser currently only works with objects that have "code" mappings here: https://github.com/golang/go/blob/go1.19beta1/src/syscall/fs_js.go#L548-L554

[Zxilly]

I think this issue has been fixed with the latest version of nodejs. I tried nodejs v22.8.0

[theoparis]

I am using Node 23.0.0 on an Asahi Linux machine, and I ran node ./scripts/run-yarn.js build:cli --no-git-hash in a checkout of yarn berry and it gave a similar error... I am assuming this is related because this is the only result when I search for this error 🤔

theo@theo-macbookpro:~/src/berry$ node ./scripts/run-yarn.js build:cli --no-git-hash
➤ YN0000: ┌ Building the CLI
panic: <object>

goroutine 7 [running]:
syscall.mapJSError({{}, 0x7ff8000100000075, 0x19bddd0})
        syscall/fs_js.go:565 +0x1e
syscall.fsCall.func1({{}, 0x0, 0x0}, {0x1815070, 0x1, 0x1})
        syscall/fs_js.go:520 +0x7
syscall/js.handleEvent()
        syscall/js/func.go:100 +0x23