bzlmod: Add support for gomock

This introduces a dependency on the new gazelle module, which requires
using Bazel at HEAD for c068b0d2347905c5e9be793b741f693c7edb6e53.

Aliases are introduced for the required gomock targets so that users
don't have to declare their own dependency on gomock with bzlmod.

.bazelci/presubmit.yml

@@ -26,7 +26,10 @@ tasks:
   ubuntu2004_bcr_tests:
     name: BCR test module
     platform: ubuntu2004
-    bazel: 6.0.0-pre.20220608.2
+    bazel: last_green
+    shell_commands:
+      # Patch io_bazel_rules_go to rules_go.
+      - curl https://raw.githubusercontent.com/bazelbuild/bazel-central-registry/main/modules/rules_go/0.33.0/patches/bcr.patch | patch -r -u -p1 -d ../..
     working_directory: tests/bcr
     build_flags:
       - "--experimental_enable_bzlmod"

MODULE.bazel

@@ -21,3 +21,8 @@ use_repo(
 go_sdk = use_extension("//go:extensions.bzl", "go_sdk")
 go_sdk.download(name = "go_default_sdk", version = "1.18.3")
 use_repo(go_sdk, "go_default_sdk")
+
+bazel_dep(name = "gazelle", version = "0.26.0")
+go_deps = use_extension("@gazelle//:extensions.bzl", "go_deps")
+go_deps.module(importpath = "github.com/golang/mock", version = "v1.6.0", sum = "h1:ErTB+efbowRARo13NNdxyJji2egdxLGQhRaY+DUumQc=")
+use_repo(go_deps, "com_github_golang_mock")

docs/go/extras/extras.md

@@ -98,7 +98,7 @@ If `source` is given, the mocks are generated in source mode; otherwise in refle
 | <a id="gomock-package"></a>package |  the name of the package the generated mocks should be in. If not specified, uses mockgen's default. See [mockgen's -package](https://github.com/golang/mock#flags) for more information.   |  <code>""</code> |
 | <a id="gomock-self_package"></a>self_package |  the full package import path for the generated code. The purpose of this flag is to prevent import cycles in the generated code by trying to include its own package. See [mockgen's -self_package](https://github.com/golang/mock#flags) for more information.   |  <code>""</code> |
 | <a id="gomock-aux_files"></a>aux_files |  a map from source files to their package path. This only needed when <code>source</code> is provided. See [mockgen's -aux_files](https://github.com/golang/mock#flags) for more information.   |  <code>{}</code> |
-| <a id="gomock-mockgen_tool"></a>mockgen_tool |  the mockgen tool to run.   |  <code>"@com_github_golang_mock//mockgen"</code> |
+| <a id="gomock-mockgen_tool"></a>mockgen_tool |  the mockgen tool to run.   |  <code>Label("//extras/gomock:mockgen")</code> |
 | <a id="gomock-imports"></a>imports |  dictionary of name-path pairs of explicit imports to use. See [mockgen's -imports](https://github.com/golang/mock#flags) for more information.   |  <code>{}</code> |
 | <a id="gomock-copyright_file"></a>copyright_file |  optional file containing copyright to prepend to the generated contents. See [mockgen's -copyright_file](https://github.com/golang/mock#flags) for more information.   |  <code>None</code> |
 | <a id="gomock-mock_names"></a>mock_names |  dictionary of interface name to mock name pairs to change the output names of the mock objects. Mock names default to 'Mock' prepended to the name of the interface. See [mockgen's -mock_names](https://github.com/golang/mock#flags) for more information.   |  <code>{}</code> |

extras/gomock.bzl

@@ -28,8 +28,8 @@ load("//go/private/rules:wrappers.bzl", go_binary = "go_binary_macro")
 load("//go/private:providers.bzl", "GoLibrary")
 load("@bazel_skylib//lib:paths.bzl", "paths")
 
-_MOCKGEN_TOOL = "@com_github_golang_mock//mockgen"
-_MOCKGEN_MODEL_LIB = "@com_github_golang_mock//mockgen/model"
+_MOCKGEN_TOOL = Label("//extras/gomock:mockgen")
+_MOCKGEN_MODEL_LIB = Label("//extras/gomock:mockgen_model")
 
 def _gomock_source_impl(ctx):
     go_ctx = go_context(ctx)
@@ -137,7 +137,7 @@ _gomock_source = rule(
         ),
         "mockgen_tool": attr.label(
             doc = "The mockgen tool to run",
-            default = Label(_MOCKGEN_TOOL),
+            default = _MOCKGEN_TOOL,
             allow_single_file = True,
             executable = True,
             cfg = "exec",
@@ -271,7 +271,7 @@ _gomock_prog_gen = rule(
         ),
         "mockgen_tool": attr.label(
             doc = "The mockgen tool to run",
-            default = Label(_MOCKGEN_TOOL),
+            default = _MOCKGEN_TOOL,
             allow_single_file = True,
             executable = True,
             cfg = "exec",
@@ -353,7 +353,7 @@ _gomock_prog_exec = rule(
         ),
         "mockgen_tool": attr.label(
             doc = "The mockgen tool to run",
-            default = Label(_MOCKGEN_TOOL),
+            default = _MOCKGEN_TOOL,
             allow_single_file = True,
             executable = True,
             cfg = "exec",

extras/gomock/BUILD.bazel

@@ -0,0 +1,17 @@
+alias(
+    name = "gomock",
+    actual = "@com_github_golang_mock//gomock",
+    visibility = ["//visibility:public"],
+)
+
+alias(
+    name = "mockgen",
+    actual = "@com_github_golang_mock//mockgen",
+    visibility = ["//visibility:public"],
+)
+
+alias(
+    name = "mockgen_model",
+    actual = "@com_github_golang_mock//mockgen/model",
+    visibility = ["//visibility:public"],
+)

tests/bcr/.bazelversion

@@ -1 +1 @@
-6.0.0-pre.20220526.1
+last_green

tests/bcr/BUILD.bazel

@@ -1,3 +1,4 @@
+load("@my_rules_go//extras:gomock.bzl", "gomock")
 load("@my_rules_go//go:def.bzl", "go_binary", "go_library", "go_test")
 
 go_library(
@@ -17,3 +18,30 @@ go_test(
     srcs = ["test.go"],
     embed = [":lib"],
 )
+
+go_library(
+    name = "mockable",
+    srcs = [
+        "mockable.go",
+    ],
+    importpath = "example.com/mockable",
+)
+
+gomock(
+    name = "mocks",
+    out = "mockable_mock.go",
+    library = ":mockable",
+    package = "mockable",
+    source = "mockable.go",
+    visibility = ["//visibility:public"],
+)
+
+go_test(
+    name = "mockable_test",
+    srcs = [
+        "mockable_mock.go",
+        "mockable_test.go",
+    ],
+    embed = [":mockable"],
+    deps = ["@my_rules_go//extras/gomock"],
+)

tests/bcr/mockable.go

@@ -0,0 +1,7 @@
+package mockable
+
+import "net/url"
+
+type Client interface {
+	Connect(addr string) url.URL
+}

tests/bcr/mockable_test.go

@@ -0,0 +1,3 @@
+package mockable
+
+var _ Client = (*MockClient)(nil)