Change https://golang.org/cl/149237 mentions this issue: go/packages: remove .s files from go list's CompiledGoFiles

.cc files too. This is pretty clearly a bug in cmd/go:

• cmd/go/internal/work/exec.go, around line 590:

	var srcfiles []string // .go and non-.go
	srcfiles = append(srcfiles, gofiles...)
	srcfiles = append(srcfiles, sfiles...)
	srcfiles = append(srcfiles, cfiles...)
	srcfiles = append(srcfiles, cxxfiles...)
	b.cacheSrcFiles(a, srcfiles)

• cacheSrcFiles eventually does: c.PutBytes(cache.Subkey(a.actionID, "srcfiles"), buf.Bytes()).

• Later, loadCachedSrcFiles does: list, _, err := c.GetBytes(cache.Subkey(a.actionID, "srcfiles")) and then a.Package.CompiledGoFiles = files.

• This makes its way into the json that cmd/go emits, which go/packages trusts absolutely.

We should make cmd/go filter out non-Go files.

There's a comment in the go/packages source code, where it manually skips .s files:

		// Workaround for https://golang.org/issue/28749.
		// TODO(adonovan): delete before go1.12 release.

If we don't fix this for 1.12, we'll have to keep the workaround in go/packages for a long time. And expand it to cover .cc, .c, .S, etc.

I'll send a CL to expand the go/packages workaround, but I think it might be good to know how risky it is to fix this yet in cmd/go.

Change https://golang.org/cl/163597 mentions this issue: go/packages: expand CompiledGoFiles workaround

Change https://golang.org/cl/313131 mentions this issue: cmd/go: don't add generated SWIG C++ files to CompiledGoFiles

Hello from the future - I just ran into this :) Would a patch be welcome?

Edit: I am also confused by the workaround in go/packages; it seems to imply this was fixed in cmd/go in Go 1.12, but I still see the same problem. For example:

$ go version
go version go1.19.1 linux/amd64
$ go list -compiled -f '{{ range $_, $file := .CompiledGoFiles}}{{$file}}{{"\n"}}{{end}}' runtime | grep -v '\.go$'
asm.s
asm_amd64.s
duff_amd64.s
memclr_amd64.s
memmove_amd64.s
preempt_amd64.s
rt0_linux_amd64.s
sys_linux_amd64.s
time_linux_amd64.s

For those wanting a workaround which isn't tied to go/packages, this worked for me:

out := pkg.CompiledGoFiles[:0]
for _, path := range pkg.CompiledGoFiles {
	switch filepath.Ext(path) {
	case "": // e.g. a generated Go file inside the build cache
	case ".go":
	default: // e.g. an assembly file
		continue
	}
	out = append(out, path)
}
pkg.CompiledGoFiles = out

Change https://go.dev/cl/451285 mentions this issue: cmd/go: don't report non-go files in CompiledGoFiles

Looking at the fix CL, I believe this bug was introduced in https://go.dev/cl/148904 (ironically, authored by @alandonovan 😅).

Heh, that fellow must be feeling pretty stupid. Thanks for the fix.

Change https://go.dev/cl/452059 mentions this issue: go/packages: change workaround for issue 28749 to not require NeedFiles

Looking forward to deleting my workaround in a year or two :)