Issue compiling go_image on macOS

[obeattie]

I am trying to compile a go_image target on macOS, and this is failing with an error about missing imports:

$ bazel build //service.api.ping:image
(20:41:03) INFO: Invocation ID: f27684c3-962f-4aba-a5d7-57245f4da640
(20:41:03) INFO: Current date is 2019-02-12
(20:41:03) INFO: Analysed target //service.api.ping:image (0 packages loaded, 0 targets configured).
(20:41:03) INFO: Found 1 target...
(20:41:04) ERROR: /private/var/tmp/_bazel_oliver/40333f6e8ec32396acff18e2ad143eea/external/org_golang_google_grpc/internal/syscall/BUILD.bazel:3:1: GoCompile external/org_golang_google_grpc/internal/syscall/linux_amd64_pure_stripped/go_default_library%/google.golang.org/grpc/internal/syscall.a failed (Exit 1) compile failed: error executing command bazel-out/host/bin/external/io_bazel_rules_go/go/tools/builders/darwin_amd64_stripped/compile -sdk external/go_sdk -installsuffix linux_amd64 -src ... (remaining 14 argument(s) skipped)

Use --sandbox_debug to see verbose messages from the sandbox
GoCompile: missing strict dependencies:
	/private/var/tmp/_bazel_oliver/40333f6e8ec32396acff18e2ad143eea/sandbox/darwin-sandbox/1/execroot/wearedev/external/org_golang_google_grpc/internal/syscall/syscall_linux.go: import of "golang.org/x/sys/unix"
Known dependencies are:
	google.golang.org/grpc/grpclog
Check that imports in Go sources match importpath attributes in deps.
Target //service.api.ping:image failed to build
Use --verbose_failures to see the command lines of failed build steps.
(20:41:04) INFO: Elapsed time: 0.600s, Critical Path: 0.20s
(20:41:04) INFO: 2 processes: 2 darwin-sandbox.
(20:41:04) FAILED: Build did NOT complete successfully

The BUILD file that I am building this from specifies goarch and goos, which I think is as you recommend it:

load("@io_bazel_rules_docker//go:image.bzl", "go_image")
load("@io_bazel_rules_go//go:def.bzl", "go_binary", "go_library")

go_library(
    deps = [
        "//bedrock:go_default_library",
        "//bedrock/filter:go_default_library",
        "//service.api.ping/handler:go_default_library",
    ],
    importpath = "github.com/monzo/wearedev/service.api.ping",
    name = "go_default_library",
    srcs = ["main.go"],
    visibility = ["//service.api.ping:__subpackages__"],
)

go_binary(
    embed = [":go_default_library"],
    name = "service.api.ping",
    out = "service.api.ping",
    visibility = ["//visibility:public"],
)

go_image(
    embed = [":go_default_library"],
    goarch = "amd64",
    goos = "linux",
    name = "image",
    pure = "on",
    visibility = ["//visibility:public"],
)

However, if I specify the platform explicitly like so, it does work:
$ bazel build --platforms=@io_bazel_rules_go//go/toolchain:linux_amd64 //service.api.ping:image

It's a little difficult to unpick precisely what's happening, but the failing compilation rule looks to be defined in rules_go, and it does look like the dependency on @org_golang_x_sys//unix:go_default_library is properly specified for the Linux platform:

https://github.com/bazelbuild/rules_go/blob/f5cfc31d4e8de28bf19d0fb1da2ab8f4be0d2cde/third_party/org_golang_google_grpc-gazelle.patch#L1532-L1535

I am pretty sure that this worked without needing to explicitly specify --platforms in a previous release, so I wonder:

• Is there a way to make this "just work" without requiring a user specify this flag?
• If not, can I somehow specify that this rule can only be built for the linux_amd64 platform? The "build platforms roadmap" seems to indicate that this is possible ("execution platform filtering") but I can't work out how to actually make use of this.

Thanks 🙏

---

• Bazel version 0.22.0
• rules_go version 0.17.0
• rules_docker version 0.7.0

[nlopezgi]

hi @obeattie,
thanks for creating this issue. I'm surprised this used to work before for you as running go_image on a Mac was not possible before platforms.
to answer your questions:

• this is the right way to use go_image from a mac; the extra platform flag is needed iiuc
• it should be possible to add an exec_compatible_with attr to the targets that can only run with this platform. But this attr is not yet supported in most rules (including these). But I'd be happy to work with you to add support. We might need to loop in @katre for advice and probably changes will be needed to rules_go too.

[obeattie]

Lightning fast! ⚡️

That's interesting that it shouldn't have worked before – I might be mistaken but I am 90% sure. In any case I don't think it matters too much; it sounds like plumbing through exec_compatible_with is the right thing to do.

If I can be of any help, I'm very happy to try and help make that a reality.

[nlopezgi]

I'll sync up with @katre to ask if this is possible /easy now or if we should wait for some of his platform features to roll out and ping back this issue.

[katre]

A couple of questions: is the problem that you cannot build the go_binary without setting --platforms to a linux platform, or that you cannot build the go_image?

Adding exec_compatible_with filters the set of execution platforms, and won't change the target platform, which seems to be the problem here.

[obeattie]

With the --platforms flag, it does work, so it's more an issue that (it seems to me) like Bazel shouldn't even try to compile go_image targets for a non-Linux platform.

[katre]

I have worded my question poorly.

1. Does bazel build //service.api.ping:go_default_library build?
2. Does bazel build --platforms=@io_bazel_rules_go//go/toolchain:linux_amd64 //service.api.ping:go_default_library build?

[katre]

I am trying to determine if the problem is with the go rules, or the docker rules.

[obeattie]

Yep, both of these commands build successfully.

[katre]

In that case, I suspect the problem is simply that the goarch and goos attributes of go_image aren't being correctly converted to a target platform.

@nlopezgi: You should probably talk to @jayconrod about the right way to handle this. Most likely, you want to do a configuration transition to set the platforms flag based on goarch and goos. Alternately, you should remove the attributes, and instruct users of passing appropriate values for the --platforms flag directly.

Using exec_compatible_with isn't going to do anything.

[jayconrod]

I think go_image passes the goos and goarch attributes to an underlying go_binary, which compiles libraries with an aspect. The aspect does not work with select expressions, so if there's anything in the transitive dependency graph that relies on select, you'll get an error like this.

There are plans to reimplement goos, goarch, and other attributes using configuration transitions. Last time I checked (early December), these weren't quite supported yet. I think they might be in Bazel 0.23.0, but I need to confirm with the folks working on it.

For now, the --platforms flag is the best way to cross-compile with rules_go. Avoid using goos and goarch if possible.

[evie404]

I hacked around this with bazel-contrib/rules_go@master...rickypai:rpai/fix_grpc_darwin

--platforms is probably the better way though

[nlopezgi]

update: our plan is to set up some examples that run on CI to exercise this use case and provide better advice / docs as to how to do this properly with the current features. From there we can move on to see effort / viability of restricting this from running with the incorrect platform.

[alex1545]

Hi @obeattie,
I'm unable to reproduce your failure. I'm still able to successfully bazel build a go_image target that specifies goarch and goos attributes on a mac. Can you please provide a minimal example for me to try and reproduce this?

[obeattie]

@alex1545 👋 I've put together a minimal proof of concept in obeattie/poc-bazel-690. If you clone this repository and try to build the //:image target on a Mac, you should reproduce the failure:

$ bazel build //:image
INFO: Invocation ID: b7914b0c-9c00-4ed0-807e-71bb073179b5
INFO: Analysed target //:image (100 packages loaded, 7737 targets configured).
INFO: Found 1 target...

…

ERROR: /private/var/tmp/_bazel_oliver/e46407b6ebc58174591c4f03b4d163aa/external/org_golang_google_grpc/internal/syscall/BUILD.bazel:3:1: GoCompile external/org_golang_google_grpc/internal/syscall/linux_amd64_pure_stripped/go_default_library%/google.golang.org/grpc/internal/syscall.a failed (Exit 1) compile failed: error executing command bazel-out/host/bin/external/io_bazel_rules_go/go/tools/builders/darwin_amd64_stripped/compile -sdk external/go_sdk -installsuffix linux_amd64 -src ... (remaining 14 argument(s) skipped)

Use --sandbox_debug to see verbose messages from the sandbox
GoCompile: missing strict dependencies:
	/private/var/tmp/_bazel_oliver/e46407b6ebc58174591c4f03b4d163aa/sandbox/darwin-sandbox/237/execroot/poc/external/org_golang_google_grpc/internal/syscall/syscall_linux.go: import of "golang.org/x/sys/unix"
Known dependencies are:
	google.golang.org/grpc/grpclog
Check that imports in Go sources match importpath attributes in deps.
Target //:image failed to build
Use --verbose_failures to see the command lines of failed build steps.
INFO: Elapsed time: 71.782s, Critical Path: 16.41s
INFO: 237 processes: 237 darwin-sandbox.
FAILED: Build did NOT complete successfully