Add support for isolated go_deps usages (#1584)

Since isolated extension usages have their own sets of tags and repos,
overrides can be allowed for such usages even in non-root modules.
These usages also have to use their own dedicated repo config file.

.bazelci/presubmit.yml

@@ -37,6 +37,7 @@ tasks:
     # Specify this target explicitly to verify that Gazelle generated it correctly.
     - "//pkg:pkg_test"
     - "//..."
+    - "@test_dep//..."
   macos_arm64:
     platform: macos_arm64
     build_targets:

.bcr/presubmit.yml

@@ -11,6 +11,8 @@ bcr_test_module:
     run_test_module:
       name: Run test module
       platform: ${{ platform }}
+      build_flags:
+      - --experimental_isolated_extension_usages
       shell_commands:
       # Regenerate the BUILD file for the test module using Gazelle.
       - rm pkg/BUILD.bazel
@@ -22,3 +24,4 @@ bcr_test_module:
       # Specify this target explicitly to verify that Gazelle generated it correctly.
       - "//pkg:pkg_test"
       - "//..."
+      - "@test_dep//..."

MODULE.bazel

@@ -36,7 +36,7 @@ use_repo(
     "org_golang_x_mod",
     "org_golang_x_sync",
     "org_golang_x_tools",
-    # Read by go_repository rules.
+    # Referenced by `gazelle_binary`.
     "bazel_gazelle_go_repository_config",
 )
 

internal/bzlmod/go_deps.bzl

@@ -29,10 +29,16 @@ the required directives to the "default_gazelle_overrides.bzl" file at \
 https://github.com/bazelbuild/bazel-gazelle/tree/master/internal/bzlmod/default_gazelle_overrides.bzl.
 """
 
-def _fail_on_non_root_overrides(module, tag_class):
+def _fail_on_non_root_overrides(module_ctx, module, tag_class):
     if module.is_root:
         return
 
+    # Isolated module extension usages only contain tags from a single module, so we can allow
+    # overrides. This is a new feature in Bazel 6.3.0, earlier versions do not allow module usages
+    # to be isolated.
+    if getattr(module_ctx, "is_isolated", False):
+        return
+
     if getattr(module.tags, tag_class):
         fail(_FORBIDDEN_OVERRIDE_TAG.format(
             tag_class = tag_class,
@@ -151,7 +157,7 @@ def _go_deps_impl(module_ctx):
             elif check_direct_deps == "error":
                 outdated_direct_dep_printer = fail
 
-        _fail_on_non_root_overrides(module, "gazelle_override")
+        _fail_on_non_root_overrides(module_ctx, module, "gazelle_override")
         for gazelle_override_tag in module.tags.gazelle_override:
             if gazelle_override_tag.path in gazelle_overrides:
                 fail("Multiple overrides defined for Go module path \"{}\" in module \"{}\".".format(gazelle_override_tag.path, module.name))
@@ -163,7 +169,7 @@ def _go_deps_impl(module_ctx):
                 build_file_generation = gazelle_override_tag.build_file_generation,
             )
 
-        _fail_on_non_root_overrides(module, "module_override")
+        _fail_on_non_root_overrides(module_ctx, module, "module_override")
         for module_override_tag in module.tags.module_override:
             if module_override_tag.path in module_overrides:
                 fail("Multiple overrides defined for Go module path \"{}\" in module \"{}\".".format(module_override_tag.path, module.name))
@@ -188,7 +194,7 @@ def _go_deps_impl(module_ctx):
                 for tag in module_tags_from_go_mod
             ]
 
-            if module.is_root:
+            if module.is_root or getattr(module_ctx, "is_isolated", False):
                 replace_map.update(go_mod_replace_map)
             else:
                 # Register this Bazel module as providing the specified Go module. It participates

internal/go_repository.bzl

@@ -280,6 +280,20 @@ def _go_repository_impl(ctx):
         # Run Gazelle
         if gazelle_path == None:
             gazelle_path = ctx.path(Label(_gazelle))
+
+        # ctx.attr.name is the canonical name of this repository, which contains a '~' if and only
+        # if this repository is generated by a module extension rather than an invocation in
+        # WORKSPACE.
+        if "~" in ctx.attr.name:
+            # TODO: In Bazel 6.3.0 and earlier, there is no way to obtain a label referencing a repo
+            # generated by an extension from within that extension. We thus have to manually
+            # construct such a label pointing to the sibling `_go_repository_config` repo created by
+            # the `go_deps` extension. All extension-generated repos have names of the form
+            # `<prefix>~<name set by the extension>`.
+            extension_repo_prefix = ctx.attr.name.rpartition("~")[0] + "~"
+            repo_config = ctx.path(Label("@@" + extension_repo_prefix + "bazel_gazelle_go_repository_config//:WORKSPACE"))
+        else:
+            repo_config = ctx.path(ctx.attr.build_config)
         cmd = [
             gazelle_path,
             "-go_repository_mode",
@@ -290,7 +304,7 @@ def _go_repository_impl(ctx):
             "-repo_root",
             ctx.path(""),
             "-repo_config",
-            ctx.path(ctx.attr.build_config),
+            repo_config,
         ]
         if ctx.attr.version:
             cmd.append("-go_repository_module_mode")

tests/bcr/.bazelignore

@@ -0,0 +1 @@
+test_dep

tests/bcr/.bazelrc

@@ -1 +1,2 @@
 common --enable_bzlmod
+common --experimental_isolated_extension_usages

tests/bcr/.bazelversion

@@ -1 +1 @@
-6.2.0
+6.3.1

tests/bcr/MODULE.bazel

@@ -8,6 +8,12 @@ local_path_override(
     path = "../..",
 )
 
+bazel_dep(name = "test_dep", version = "1.0.0")
+local_path_override(
+    module_name = "test_dep",
+    path = "test_dep",
+)
+
 bazel_dep(name = "rules_go", version = "0.39.1", repo_name = "my_rules_go")
 
 # This bazel_dep provides the Go dependency github.com/cloudflare/circl, which requires custom

tests/bcr/test_dep/BUILD.bazel

@@ -0,0 +1,8 @@
+load("@rules_go//go:def.bzl", "go_test")
+
+go_test(
+    name = "test",
+    srcs = ["test.go"],
+    visibility = ["//visibility:public"],
+    deps = ["@com_github_stretchr_testify//require"],
+)

tests/bcr/test_dep/MODULE.bazel

@@ -0,0 +1,50 @@
+module(
+    name = "test_dep",
+    version = "1.0.0",
+)
+
+bazel_dep(name = "rules_go", version = "0.41.0")
+bazel_dep(name = "gazelle", version = "0.31.0")
+
+# An isolated extension usage does not share any tags with any other usage and results in a
+# completely separate set of repos. We explicitly use different directives and patches here to
+# verify that they do not interfere with those of the root test module.
+go_deps = use_extension("@gazelle//:extensions.bzl", "go_deps", isolate = True)
+go_deps.module(
+    path = "github.com/stretchr/testify",
+    sum = "h1:pSgiaMZlXftHpm5L7V1+rVB+AZJydKsMxsQBIJw4PKk=",
+    version = "v1.8.0",
+)
+go_deps.gazelle_override(
+    directives = [
+        "gazelle:go_naming_convention import",
+    ],
+    path = "github.com/stretchr/testify",
+)
+go_deps.module_override(
+    patch_strip = 1,
+    patches = [
+        "//patches:testify.patch",
+    ],
+    path = "github.com/stretchr/testify",
+)
+
+go_deps.module(
+    indirect = True,
+    path = "gopkg.in/yaml.v3",
+    sum = "h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=",
+    version = "v3.0.1",
+)
+go_deps.gazelle_override(
+    path = "gopkg.in/yaml.v3",
+    directives = [
+        "gazelle:go_naming_convention import",
+    ],
+)
+go_deps.module(
+    indirect = True,
+    path = "github.com/davecgh/go-spew",
+    sum = "h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=",
+    version = "v1.1.1",
+)
+use_repo(go_deps, "com_github_stretchr_testify")

tests/bcr/test_dep/patches/testify.patch

@@ -0,0 +1,13 @@
+diff --git a/require/require.go b/require/require.go
+index a6e1b7c..bc21879 100644
+--- a/require/require.go
++++ b/require/require.go
+@@ -12,6 +12,8 @@ import (
+ 	time "time"
+ )
+
++const Hello = "not_hello"
++
+ // Condition uses a Comparison to assert a complex condition.
+ func Condition(t TestingT, comp assert.Comparison, msgAndArgs ...interface{}) {
+ 	if h, ok := t.(tHelper); ok {

tests/bcr/test_dep/test.go

@@ -0,0 +1,13 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestPatch(t *testing.T) {
+	// A patch is used to add this constant with a value that differs from that patched into the
+	// root module's version of this dep.
+	require.Equal(t, "not_hello", require.Hello)
+}