Enable building kubectl hermetically as part of toolchain setup

k8s/k8s.bzl

@@ -35,13 +35,15 @@ py_library(
     strip_prefix = "PyYAML-3.12/lib/yaml",
   )
 
-  # Register the default kubectl toolchain that expects the 'kubectl'
-  # executable to be in the PATH
+  # Register the default kubectl toolchain targets for supported platforms
+  # note these work with the autoconfigured toolchain
   native.register_toolchains(
     "@io_bazel_rules_k8s//toolchains/kubectl:kubectl_linux_toolchain",
     "@io_bazel_rules_k8s//toolchains/kubectl:kubectl_osx_toolchain",
     "@io_bazel_rules_k8s//toolchains/kubectl:kubectl_windows_toolchain",
   )
 
-  # WORKSPACE target to configure the kubectl tool
-  kubectl_configure(name = "local_k8s_config")
+  excludes = native.existing_rules().keys()
+  if "k8s_config" not in excludes:
+    # WORKSPACE target to configure the kubectl tool
+    kubectl_configure(name = "k8s_config", build_srcs = True)

k8s/object.bzl

@@ -173,9 +173,13 @@ def _common_impl(ctx):
         namespace_arg = "--namespace=\"" + namespace_arg + "\""
 
     kubectl_tool_info = ctx.toolchains["@io_bazel_rules_k8s//toolchains/kubectl:toolchain_type"].kubectlinfo
+    kubectl_tool = kubectl_tool_info.tool_path
+    if not kubectl_tool_info.tool_path:
+        kubectl_tool = _runfiles(ctx, kubectl_tool_info.tool_target.files.to_list()[0])
+        files += kubectl_tool_info.tool_target.files.to_list()
 
     substitutions = {
-        "%{kubectl_tool}": kubectl_tool_info.tool_path,
+        "%{kubectl_tool}": kubectl_tool,
         "%{cluster}": cluster_arg,
         "%{context}": context_arg,
         "%{user}": user_arg,

toolchains/kubectl/BUILD

@@ -32,7 +32,7 @@ toolchain(
         "@bazel_tools//platforms:linux",
         "@bazel_tools//platforms:x86_64",
     ],
-    toolchain = "@local_k8s_config//:toolchain",
+    toolchain = "@k8s_config//:toolchain",
     toolchain_type = ":toolchain_type",
 )
 
@@ -42,7 +42,7 @@ toolchain(
         "@bazel_tools//platforms:osx",
         "@bazel_tools//platforms:x86_64",
     ],
-    toolchain = "@local_k8s_config//:toolchain",
+    toolchain = "@k8s_config//:toolchain",
     toolchain_type = ":toolchain_type",
 )
 
@@ -52,6 +52,6 @@ toolchain(
         "@bazel_tools//platforms:windows",
         "@bazel_tools//platforms:x86_64",
     ],
-    toolchain = "@local_k8s_config//:toolchain",
+    toolchain = "@k8s_config//:toolchain",
     toolchain_type = ":toolchain_type",
 )

toolchains/kubectl/BUILD.target.tpl

@@ -0,0 +1,25 @@
+# Copyright 2018 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""
+This BUILD file is auto-generated from toolchains/kubectl/BUILD.tpl
+"""
+
+package(default_visibility = ["//visibility:public"])
+
+load("@io_bazel_rules_k8s//toolchains/kubectl:kubectl_toolchain.bzl", "kubectl_toolchain")
+
+kubectl_toolchain(
+    name = "toolchain",
+    tool_target = "%{KUBECTL_TARGET}",
+)

toolchains/kubectl/kubectl_configure.bzl

@@ -16,16 +16,79 @@ Defines a repository rule for configuring the kubectl tool.
 """
 
 def _impl(repository_ctx):
-
-    kubectl_tool_path = repository_ctx.which("kubectl")
+    substitutions = None
+    label = None
+    if repository_ctx.attr.build_srcs:
+        kubectl_target = "@io_kubernetes//cmd/kubectl:kubectl"
+        substitutions = {"%{KUBECTL_TARGET}": "%s" % kubectl_target}
+        template = Label("@io_bazel_rules_k8s//toolchains/kubectl:BUILD.target.tpl")
+    else:
+        kubectl_tool_path = repository_ctx.which("kubectl")
+        substitutions = {"%{KUBECTL_TOOL}": "%s" % kubectl_tool_path}
+        template = Label("@io_bazel_rules_k8s//toolchains/kubectl:BUILD.path.tpl")
 
     repository_ctx.template(
         "BUILD",
-        Label("@io_bazel_rules_k8s//toolchains/kubectl:BUILD.tpl"),
-        {"%{KUBECTL_TOOL}": "%s" % kubectl_tool_path},
-        False
+        template,
+        substitutions,
+        False,
     )
 
-kubectl_configure = repository_rule(
+_kubectl_configure = repository_rule(
     implementation = _impl,
+    attrs = {
+        "build_srcs": attr.bool(
+            doc = "Optional. Set to true to build kubectl from sources.",
+            default = False,
+            mandatory = False,
+        ),
+    },
 )
+
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+
+def kubectl_configure(name, **kwargs):
+    """
+    Creates an external repository with a kubectl_toolchain target
+    properly configured.
+
+    Args:
+        **kwargs:
+      Required Args
+        name: A unique name for this rule.
+      Default Args:
+        build_srcs: Optional. Set to true to build kubectl from sources. Default: False
+        k8s_commit: Otional. Commit / release tag at which to build kubectl
+          from. Default "v1.13.0-beta.1"
+        k8s_sha256: Otional. sha256 of commit at which to build kubectl from.
+          Default <valid sha for default version>.
+        k8s_prefix: Otional. Prefix to strip from commit / release archive.
+          Typically the same as the commit, or Kubernetes-<release tag>.
+          Default <valid prefix for default version>.
+      Note: Not all versions/commits of kubernetes project can be used to compile
+      kubectl from an external repo. Notably, we have only tested with v1.13.0-beta.1
+      or above. Note this rule has a hardcoded pointer to io_kubernetes_build repo
+      if your commit (above v1.13.0-beta.1) does not work due to problems,
+      related to @io_kubernetes_build repo, please send a PR to update these values.
+    """
+    build_srcs = False
+    if "build_srcs" in kwargs and kwargs["build_srcs"]:
+        build_srcs = True
+
+        # We keep these defaults here as they are only used by in this macro and not by the repo rule.
+        k8s_commit = kwargs["k8s_commit"] if "k8s_commit" in kwargs else "v1.13.0-beta.1"
+        k8s_sha256 = kwargs["k8s_sha256"] if "k8s_sha256" in kwargs else "dfb39ce36284c1ce228954ca12bf016c09be61e40a875e8af4fff84e116bd3a7"
+        k8s_prefix = kwargs["k8s_prefix"] if "k8s_prefix" in kwargs else "kubernetes-1.13.0-beta.1"
+        http_archive(
+            name = "io_kubernetes",
+            sha256 = k8s_sha256,
+            strip_prefix = k8s_prefix,
+            urls = [("https://github.com/kubernetes/kubernetes/archive/%s.tar.gz" % k8s_commit)],
+        )
+        http_archive(
+            name = "io_kubernetes_build",
+            sha256 = "21160531ea8a9a4001610223ad815622bf60671d308988c7057168a495a7e2e8",
+            strip_prefix = "repo-infra-b4bc4f1552c7fc1d4654753ca9b0e5e13883429f",
+            urls = ["https://github.com/kubernetes/repo-infra/archive/b4bc4f1552c7fc1d4654753ca9b0e5e13883429f.tar.gz"],
+        )
+    _kubectl_configure(name = name, build_srcs = build_srcs)

toolchains/kubectl/kubectl_toolchain.bzl

@@ -19,20 +19,31 @@ KubectlInfo = provider(
     doc = "Information about how to invoke the kubectl tool.",
     fields = {
         "tool_path": "Path to the kubectl executable",
+        "tool_target": "Target to build kubectl executable",
     },
 )
 
 def _kubectl_toolchain_impl(ctx):
+    if not ctx.attr.tool_path and not ctx.attr.tool_target:
+        fail("Invalid kubectl_toolchain. kubectl_toolchain must have either tool_path or tool_target.")
     toolchain_info = platform_common.ToolchainInfo(
         kubectlinfo = KubectlInfo(
             tool_path = ctx.attr.tool_path,
+            tool_target = ctx.attr.tool_target,
         ),
     )
     return [toolchain_info]
 
 kubectl_toolchain = rule(
     implementation = _kubectl_toolchain_impl,
     attrs = {
-        "tool_path": attr.string(),
+        "tool_path": attr.string(
+            doc = "Absolute path to a pre-installed kubectl binary.",
+            mandatory = False,
+        ),
+        "tool_target": attr.label(
+            doc = "Target to build kubectl from source.",
+            mandatory = False,
+        ),
     },
 )