cmd/go: GOOS=js GOARCH=wasm go build -o [non-empty parent dir] ./... fails on Windows host

[Gregory-Ledray]

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

$ go version
go version go1.14 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=amd64
set GOBIN=
set GOCACHE=C:\Users\gledr\AppData\Local\go-build
set GOENV=C:\Users\gledr\AppData\Roaming\go\env
set GOEXE=.exe
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOINSECURE=
set GONOPROXY=
set GONOSUMDB=
set GOOS=windows
set GOPATH=C:\Users\gledr\Polyapp_Apps\gocode
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 AR=ar
set CC=gcc
set CXX=g++
set CGO_ENABLED=1
set GOMOD=C:\Users\gledr\Polyapp_Apps\gocode\src\gitlab.com\polyapp-open-source\poly\go.mod
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=-m64 -mthreads -fmessage-length=0 -fdebug-prefix-map=C:\Users\gledr\AppData\Local\Temp\go-build442293962=/tmp/go-build -gno-record-gcc-switches

What did you do?

I was checking out the changes in #14295 and they work great most of the time, but I might have found an edge case where they fail.

The changes in #14295 work great with regular GOOS and GOARCH on non-empty directories (nice work!):

gledr@LAPTOP-AH6IAHBO MINGW64 ~/Polyapp_Apps/gocode/src/gitlab.com/polyapp-open-source/poly/testdata (CI-expansion)
$ go list ./...
gitlab.com/polyapp-open-source/poly/testdata/cmd
gitlab.com/polyapp-open-source/poly/testdata/cmd/hello

gledr@LAPTOP-AH6IAHBO MINGW64 ~/Polyapp_Apps/gocode/src/gitlab.com/polyapp-open-source/poly/testdata (CI-expansion)
$ ls ./cmd
hello  main.go  wasm1  wasm2  wasm3

gledr@LAPTOP-AH6IAHBO MINGW64 ~/Polyapp_Apps/gocode/src/gitlab.com/polyapp-open-source/poly/testdata (CI-expansion)
$ go build -o ./cmd ./...

gledr@LAPTOP-AH6IAHBO MINGW64 ~/Polyapp_Apps/gocode/src/gitlab.com/polyapp-open-source/poly/testdata (CI-expansion)
$ ls ./cmd
cmd.exe  hello  hello.exe  main.go  wasm1  wasm2  wasm3

But doesn't work with GOOS=js GOARCH=wasm

gledr@LAPTOP-AH6IAHBO MINGW64 ~/Polyapp_Apps/gocode/src/gitlab.com/polyapp-open-source/poly/testdata (CI-expansion)
$ GOOS=js GOARCH=wasm go list ./...
gitlab.com/polyapp-open-source/poly/testdata/cmd
gitlab.com/polyapp-open-source/poly/testdata/cmd/hello
gitlab.com/polyapp-open-source/poly/testdata/cmd/wasm1
gitlab.com/polyapp-open-source/poly/testdata/cmd/wasm2
gitlab.com/polyapp-open-source/poly/testdata/cmd/wasm3

gledr@LAPTOP-AH6IAHBO MINGW64 ~/Polyapp_Apps/gocode/src/gitlab.com/polyapp-open-source/poly/testdata (CI-expansion)
$ ls ./cmd
hello  main.go  wasm1  wasm2  wasm3

gledr@LAPTOP-AH6IAHBO MINGW64 ~/Polyapp_Apps/gocode/src/gitlab.com/polyapp-open-source/poly/testdata (CI-expansion)
$ GOOS=js GOARCH=wasm go build -o ./cmd ./...
go build gitlab.com/polyapp-open-source/poly/testdata/cmd/wasm1: build output "cmd\\wasm1" already exists and is a directory
go build gitlab.com/polyapp-open-source/poly/testdata/cmd/wasm2: build output "cmd\\wasm2" already exists and is a directory
go build gitlab.com/polyapp-open-source/poly/testdata/cmd/wasm3: build output "cmd\\wasm3" already exists and is a directory
go build gitlab.com/polyapp-open-source/poly/testdata/cmd/hello: build output "cmd\\hello" already exists and is a directory

It works great with GOOS=js GOARCH=wasm if I make a new directory:

gledr@LAPTOP-AH6IAHBO MINGW64 ~/Polyapp_Apps/gocode/src/gitlab.com/polyapp-open-source/poly/testdata
(CI-expansion)
$ ls ./cmd
hello  main.go  wasm1  wasm2  wasm3

gledr@LAPTOP-AH6IAHBO MINGW64 ~/Polyapp_Apps/gocode/src/gitlab.com/polyapp-open-source/poly/testdata
(CI-expansion)
$ ls ./bin
ls: cannot access './bin': No such file or directory

gledr@LAPTOP-AH6IAHBO MINGW64 ~/Polyapp_Apps/gocode/src/gitlab.com/polyapp-open-source/poly/testdata (CI-expansion)
$ GOOS=js GOARCH=wasm go list ./...
gitlab.com/polyapp-open-source/poly/testdata/cmd
gitlab.com/polyapp-open-source/poly/testdata/cmd/hello
gitlab.com/polyapp-open-source/poly/testdata/cmd/wasm1
gitlab.com/polyapp-open-source/poly/testdata/cmd/wasm2
gitlab.com/polyapp-open-source/poly/testdata/cmd/wasm3

gledr@LAPTOP-AH6IAHBO MINGW64 ~/Polyapp_Apps/gocode/src/gitlab.com/polyapp-open-source/poly/testdata
(CI-expansion)
$ mkdir ./bin

gledr@LAPTOP-AH6IAHBO MINGW64 ~/Polyapp_Apps/gocode/src/gitlab.com/polyapp-open-source/poly/testdata (CI-expansion)
$ GOOS=js GOARCH=wasm go build -o ./bin ./...

gledr@LAPTOP-AH6IAHBO MINGW64 ~/Polyapp_Apps/gocode/src/gitlab.com/polyapp-open-source/poly/testdata (CI-expansion)
$ ls ./bin
cmd  hello  wasm1  wasm2  wasm3

And it works great if I rebuild into the bin directory:

gledr@LAPTOP-AH6IAHBO MINGW64 ~/Polyapp_Apps/gocode/src/gitlab.com/polyapp-open-source/poly/testdata (CI-expansion)
$ GOOS=js GOARCH=wasm go build -o ./bin ./...

gledr@LAPTOP-AH6IAHBO MINGW64 ~/Polyapp_Apps/gocode/src/gitlab.com/polyapp-open-source/poly/testdata (CI-expansion)
$ rm ./bin/cmd ./bin/hello ./bin/wasm2

gledr@LAPTOP-AH6IAHBO MINGW64 ~/Polyapp_Apps/gocode/src/gitlab.com/polyapp-open-source/poly/testdata (CI-expansion)
$ GOOS=js GOARCH=wasm go build -o ./bin ./...

Is this intended to work with non-empty parent directories of the binaries? Why does it work with GOOS=windows GOARCH=amd64 but not GOOS=js GOARCH=wasm?

My directory structure lives inside $GOPATH at ~/Polyapp_Apps/gocode/src/gitlab.com/polyapp-open-source/poly/testdata because, setting the exact issue aside, I'm writing some tools to make linting, testing, building, and running my multi-arch. programs a bit easier.

testdata/
    cmd/
        hello/
            main.go
            main_test.go
        wasm1/
            main_js_wasm.go
        wasm2/
            main_js_wasm.go
        wasm3/
            main.go
        main.go

Here are my test files in order of the directory structure. Some files have perhaps changed a bit since I ran the commands above - I don't recall if the test file existed before

testdata/cmd/hello/main.go

package main

import (
	"fmt"
	"os"
)

func main() {
	fmt.Println("Hello from poly/testdata/cmd/hello/main.go")

	osCheck()
}

// osCheck returns true for success using syscalls and false otherwise
func osCheck() bool {
	_, err := os.Stat(".")
	if err != nil {
		fmt.Println("os.Stat failed: " + err.Error())
		return false
	}
	return true
}

testdata/cmd/hello/main_test.go

package main

import "testing"

func TestOsCheck(t *testing.T) {
	chk := osCheck()
	if chk == false {
		t.Fatal("couldn't stat")
	}
}

testdata/cmd/wasm1/main_js_wasm.go

// +build js

package main

import "fmt"

func main() {
	fmt.Println("hello from testdata/cmd/wasm1/main_js_wasm.go")
}

testdata/cmd/wasm2/main_js_wasm.go

// +build js

package main

import "fmt"

func main() {
	fmt.Println("hello from testdata/cmd/wasm2/main_js_wasm.go")
}

testdata/cmd/wasm3/main.go

// +build js

package main

import "fmt"

func main() {
	fmt.Println("Hello from testdata/cmd/wasm3/main.go")
}

testdata/cmd/main.go

package main

import "fmt"

func main() {
	fmt.Println("Hello from poly/testdata/cmd/main.go")
}

[bcmills]

CC @jayconrod @matloob @neelance @cherrymui

[bcmills]

Looking at your go env output, you appear to be running the go build command on a Windows host? That's probably a relevant detail.

[cherrymui]

$ GOOS=js GOARCH=wasm go build -o ./cmd ./...

You're trying to write output files cmd/wasm1, cmd/wasm2, etc., but these paths already exist and are directories, so it cannot overwrite it, as the error message clearly stated.

Writing to any other directories where there aren't such paths should work.

Why does it work with GOOS=windows GOARCH=amd64 but not GOOS=js GOARCH=wasm?

Because cmd/wasm1, etc. are build-tagged for wasm. It doesn't build on windows.

[cherrymui]

Closing as this works as intended.

[bcmills]

Oh! The outputs for the default GOOS=windows have a .exe suffix.

That's what avoids the collision with the existing directories for non-build-tagged binaries.