Fix or update build files when syncing

[jayconrod]

A build failure was originally reported in bazel-contrib/rules_go#1356. It appears that Bazel BUILD files in api, apimachinery, and client-go refer to non-existent packages.

Steps to reproduce

• In an empty workspace, create an empty BUILD file and a WORKSPACE file like below:

http_archive(
    name = "io_bazel_rules_go",
    sha256 = "4b14d8dd31c6dbaf3ff871adcd03f28c3274e42abc855cb8fb4d01233c0154dc",
    url = "https://github.com/bazelbuild/rules_go/releases/download/0.10.1/rules_go-0.10.1.tar.gz",
)

http_archive(
    name = "bazel_gazelle",
    sha256 = "6228d9618ab9536892aa69082c063207c91e777e51bd3c5544c9c060cafe1bd8",
    url = "https://github.com/bazelbuild/bazel-gazelle/releases/download/0.10.0/bazel-gazelle-0.10.0.tar.gz",
)

load("@io_bazel_rules_go//go:def.bzl", "go_rules_dependencies", "go_register_toolchains")

go_rules_dependencies()

go_register_toolchains()

load("@bazel_gazelle//:deps.bzl", "gazelle_dependencies")

gazelle_dependencies()

load("@bazel_gazelle//:def.bzl", "go_repository")

git_repository(
    name = "io_k8s_api",
    remote = "https://github.com/kubernetes/api",
    tag = "kubernetes-1.9.3",
)

git_repository(
    name = "io_k8s_apimachinery",
    remote = "https://github.com/kubernetes/apimachinery",
    tag = "kubernetes-1.9.3",
)

git_repository(
    name = "io_k8s_client_go",
    remote = "https://github.com/kubernetes/client-go",
    tag = "v6.0.0",
)

• Run this command:

$ bazel build @io_k8s_client_go//kubernetes/typed/core/v1:go_default_library
ERROR: /usr/local/google/home/jayconrod/.cache/bazel/_bazel_jayconrod/533bcca7b8c77451fbaf7e2a9f7692b3/external/io_k8s_client_go/kubernetes/typed/core/v1/BUILD:8:1: no such package '@io_k8s_client_go//vendor/k8s.io/apimachinery/pkg/types': BUILD file not found on package path and referenced by '@io_k8s_client_go//kubernetes/typed/core/v1:go_default_library'.
ERROR: Analysis of target '@io_k8s_client_go//kubernetes/typed/core/v1:go_default_library' failed; build aborted: no such package '@io_k8s_client_go//vendor/k8s.io/apimachinery/pkg/types': BUILD file not found on package path.

Analysis

The BUILD file for the package @io_k8s_client_go//kubernetes/typed/core/v1 refers to rules in //vendor/k8s.io/.... That directory doesn't exist in this repository.

I suspect this bot may have copied the source files from k/k without updating the build files. Not sure what the right answer is. If the bot removes build files during sync, it may be possible to regenerate them correctly with Gazelle via go_repository. If the bot updates build files using Gazelle during sync, all dependencies will need to be vendored or declared using external repositories in WORKSPACE.

[jayconrod]

cc @ixdy @jmhodges

[sttts]

Just to make sure we are talking about the same thing: this is about using client-go in an external project that builds with bazel?

[jmhodges]

Yep, that's what we're talking about. (I'm a non-Googler who is trying to do this)

[ixdy]

My first take was that we hadn't encountered this issue before because most kubernetes extensions use go vendoring, and gazelle generally fixes the BUILD rules appropriately.

But then I read https://github.com/kubernetes/client-go/blob/d902e7da4bfa28d901dca2cb81b76e40ee7703ae/INSTALL.md and learned that it's recommended you go get -u k8s.io/api-machinery/... to get the necessary dependencies. So it's decidedly different from the main kubernetes/kubernetes repo.

I guess one approach which would fix this for bazel would be to add the necessary dependencies to the bazel WORKSPACE for the published repos as @jmhodges did above, along with rewriting the BUILD rules during publishing so they're internally consistent. This likely wouldn't change anything for non-bazel consumers, though maintenance becomes more tricky. I'm also not sure how to make this interoperate well with kubernetes/kubernetes, where we don't currently have any go dependencies in the bazel WORKSPACE.

[ixdy]

as @jmhodges points out in bazel-contrib/rules_go#1356, it's also a bit weird that we publish BUILD files but not WORKSPACE files for the published repositories.

maybe we should at least remove the BUILD files from the published repos until we have a better story for making them consumable downstream.

[sttts]

Without deeper understanding of bazel, removing the BUILD files sounds fine.

[jmhodges]

Would love to see that BUILD file deletion happen!

[sttts]

#50 needs a review. https://github.com/sttts/client-go is the output of the bot with that patch.