Bazel: how to import/build a go_binary for a go_test

I'm using bazel to run a go test on my CI system. The go test will need to use a helper binary built from another go file.

The dir structure looks like the following:

    some/of/my/path
    ├── BUILD.bazel
    ├── my_utils.go
    ├── my_test.go
    └── my_tool
        ├── BUILD.bazel
        └── my_tool.go

I.e. the code in my_test.go is going to use the executable binary built from dir my_tool.

In a non-bazel case, I can just go build ./mytool to get the executable binary that my_test.go needs. To accommodate this the bazel world, I write the following in the bazel files:

• In some/of/my/path/BUILD.bazel:

    load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
    
    go_library(
        name = "testutils",
        srcs = ["my_utils.go"],
        importpath = "some/of/my/path",
        visibility = ["//visibility:public"],
        deps = [
            "@org_golang_x_net//context",
            ... (some other dependencies, not related)
        ],
    )
    
    go_test(
        name = "my_test",
        size = "enormous",
        srcs = ["mytest.go"],
        embed = [":testutils"],
        deps = [
            "//some/of/my/path/my_tool:my_tool",
        ],
    )

• In some/of/my/path/my_tool/BUILD.bazel

    load("@io_bazel_rules_go//go:def.bzl", "go_binary", "go_library")
    
    go_library(
        name = "my_tool_lib",
        srcs = ["my_tool.go"],
        importpath = "some/of/my/path/my_tool",
        visibility = ["//visibility:private"],
        deps = ["some dependency"],
    )
    
    go_binary(
        name = "my_tool",
        embed = [":my_tool_lib"],
        visibility = ["//visibility:public"],
    )

So the idea is when I hit bazel run, it will build the my_tool go binary, which the go test my_test can use (see the deps field of the go test).

While in the CI I hit this error:

    ERROR: /home/agent/work/.go/src/some/of/my/path/BUILD.bazel:20:8: in go_test rule //some/of/my/path:my_test:
    Traceback (most recent call last):
      File "/home/agent/.cache/bazel/_bazel_agent/40f5e2a2e18a7cdb4cd075f919d8072b/external/io_bazel_rules_go/go/private/rules/test.bzl", line 66, column 43, in _go_test_impl
        internal_source = go.library_to_source(go, ctx.attr, internal_library, ctx.coverage_instrumented())
      File "/home/agent/.cache/bazel/_bazel_agent/40f5e2a2e18a7cdb4cd075f919d8072b/external/io_bazel_rules_go/go/private/context.bzl", line 247, column 26, in _library_to_source
        _check_binary_dep(go, dep, "deps")
      File "/home/agent/.cache/bazel/_bazel_agent/40f5e2a2e18a7cdb4cd075f919d8072b/external/io_bazel_rules_go/go/private/context.bzl", line 295, column 13, in _check_binary_dep
        fail("rule {rule} depends on executable {dep} via {edge}. This is not safe for cross-compilation. Depend on go_library instead.".format(
    Error in fail: rule //some/of/my/path:my_test depends on executable //some/of/my/path/my_tool:my_tool via deps. This is not safe for cross-compilation. Depend on go_library instead.
    ERROR: Analysis of target '//some/of/my/path:my_test' failed; build aborted: Analysis of target '//some/of/my/path:my_test' failed
    INFO: Elapsed time: 79.552s
    INFO: 0 processes.
    FAILED: Build did NOT complete successfully (595 packages loaded, 12182 targets configured)
    ERROR: Build failed. Not running target
    FAILED: Build did NOT complete successfully (595 packages loaded, 12182 targets configured)
    Process exited with code 1

But my goal is to use the binary. How should I change the configs to achieve that?

You want data, not deps. deps is for things linked into a binary, data is for things the binary uses at runtime.

Once your binary is in data, use runfiles.go to run it. Add @io_bazel_rules_go//go/tools/bazel:go_default_library to deps (it's a library you want linked in), and then use FindBinary to find the path.