cmd/go: go get in module mode does not initialize git submodules

[BenLubar]

Please answer these questions before submitting your issue. Thanks!

What did you do?

If possible, provide a recipe for reproducing the error.
A complete runnable program is good.
A link on play.golang.org is best.

# In a directory outside of $GOPATH:
go mod -init -module example.invalid/gapstone-test
go get github.com/benlubar/gapstone@go-get

What did you expect to see?

Successful completion of the command.

What did you see instead?

go: finding github.com/benlubar/gapstone go-get
go: downloading github.com/benlubar/gapstone v0.0.0-20180731154137-aefb8fb9d854
# github.com/benlubar/gapstone
..\..\..\go\src\mod\github.com\benlubar\[email protected]\arm64_constants.go:19:32: fatal error: capstone/capstone.h: No such file or directory
 // #include <capstone/capstone.h>
                                ^
compilation terminated.

Does this issue reproduce with the latest release (go1.10.3)?

No. Go 1.10.3 correctly initializes the git submodule, as does go1.11beta2 when not using go.mod.

System details

go version go1.11beta2 windows/amd64
GOARCH="amd64"
GOBIN=""
GOCACHE="C:\Users\Owner\AppData\Local\go-build"
GOEXE=".exe"
GOHOSTARCH="amd64"
GOHOSTOS="windows"
GOOS="windows"
GOPATH="C:\Users\Owner\go"
GOPROXY=""
GORACE=""
GOROOT="C:\tools\go"
GOTMPDIR=""
GOTOOLDIR="C:\tools\go\pkg\tool\windows_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="C:\Users\Owner\Source\Repos\gapstone-test\go.mod"
GOROOT/bin/go version: go version go1.11beta2 windows/amd64
GOROOT/bin/go tool compile -V: compile version go1.11beta2
gdb --version: GNU gdb (GDB) 7.10.1

[BenLubar]

As a side note, this fails with a different error message if you capitalize my GitHub username in the import path:

go: finding github.com/BenLubar/gapstone go-get
go: downloading github.com/BenLubar/gapstone v0.0.0-20180731154137-aefb8fb9d854
can't load package: package github.com/BenLubar/gapstone: C:\Users\Owner\go\src\mod\github.com\!ben!lubar\[email protected]\engine.go: malformed #cgo argument: -IC:/Users/Owner/go/src/mod/github.com/!ben!lubar/[email protected]/include

I assume this is because cgo doesn't like ! in paths.

[myitcv]

Git submodules are not going to be supported per #24094 (comment)

Leaving this issue open however for the cgo issue

cc @ianlancetaylor

[ianlancetaylor]

The go tool is working as intended in rejecting cgo file names that contain !. For 1.11 this is documented at https://tip.golang.org/cmd/cgo. Closing as I don't think there is anything we are going to do here; please comment if you disagree.

[myitcv]

@ianlancetaylor I think the ! is as a result of https://go-review.googlesource.com/c/go/+/124378

So cc-ed you just to ensure everything is working as intended post that?

[ianlancetaylor]

@myitcv Thanks for pointing that out.

[gopherbot]

Change https://golang.org/cl/127297 mentions this issue: go/build: accept ! in cgo arguments