Add visibility extension to support recursive default_visibility conf…

…iguration (bazelbuild#783)

Under a new /bazel/ subdirectory, this language-agnostic extension allows a directive to control the default_visibility templated out to all BUILD.bazel files in or under the directory. This feature is intended to allow large codebases to define hierarchical visibility defaults.

.gitignore

@@ -6,3 +6,4 @@
 /tests/bcr/bazel-bin
 /tests/bcr/bazel-out
 /tests/bcr/bazel-testlogs
+.DS_STORE

language/BUILD.bazel

@@ -26,6 +26,7 @@ filegroup(
         "base.go",
         "lang.go",
         "update.go",
+        "//language/bazel:all_files",
         "//language/go:all_files",
         "//language/proto:all_files",
     ],

language/bazel/BUILD.bazel

@@ -0,0 +1,9 @@
+filegroup(
+    name = "all_files",
+    testonly = True,
+    srcs = [
+        "BUILD.bazel",
+        "//language/bazel/visibility:all_files",
+    ],
+    visibility = ["//visibility:public"],
+)

language/bazel/visibility/BUILD.bazel

@@ -0,0 +1,52 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
+
+go_library(
+    name = "visibility",
+    srcs = [
+        "config.go",
+        "lang.go",
+        "resolve.go",
+    ],
+    importpath = "github.com/bazelbuild/bazel-gazelle/language/bazel/visibility",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//config",
+        "//label",
+        "//language",
+        "//repo",
+        "//resolve",
+        "//rule",
+    ],
+)
+
+alias(
+    name = "go_default_library",
+    actual = ":visibility",
+    visibility = ["//visibility:public"],
+)
+
+go_test(
+    name = "visibility_test",
+    srcs = ["lang_test.go"],
+    deps = [
+        ":visibility",
+        "//config",
+        "//label",
+        "//language",
+        "//rule",
+        "@com_github_stretchr_testify//require:go_default_library",
+    ],
+)
+
+filegroup(
+    name = "all_files",
+    testonly = True,
+    srcs = [
+        "BUILD.bazel",
+        "config.go",
+        "lang.go",
+        "lang_test.go",
+        "resolve.go",
+    ],
+    visibility = ["//visibility:public"],
+)

language/bazel/visibility/config.go

@@ -0,0 +1,64 @@
+package visibility
+
+import (
+	"flag"
+	"strings"
+
+	"github.com/bazelbuild/bazel-gazelle/config"
+	"github.com/bazelbuild/bazel-gazelle/rule"
+)
+
+const (
+	_directiveName = "default_visibility"
+)
+
+type visConfig struct {
+	visibilityTargets []string
+}
+
+// getVisConfig directly returns the internal configuration struct rather
+// than a pointer because we explicitly want pass-by-value symantics so
+// configurations down a directory tree don't accidentially update upstream.
+func getVisConfig(c *config.Config) visConfig {
+	cfg := c.Exts[_extName]
+	if cfg == nil {
+		return visConfig{}
+	}
+	return cfg.(visConfig)
+}
+
+// RegisterFlags noops because we only parameterize behavior with a directive.
+func (*visibilityExtension) RegisterFlags(fs *flag.FlagSet, cmd string, c *config.Config) {}
+
+// CheckFlags noops because no flags are referenced.
+func (*visibilityExtension) CheckFlags(fs *flag.FlagSet, c *config.Config) error {
+	return nil
+}
+
+// KnownDirectives returns the only directive this extension operates on.
+func (*visibilityExtension) KnownDirectives() []string {
+	return []string{_directiveName}
+}
+
+// Configure identifies the visibility targets from the directive value, if it exists.
+//
+// To set multiple visibility targets, either multiple directives can be used, or a
+// list can be provided with comma-separated values.
+func (*visibilityExtension) Configure(c *config.Config, _ string, f *rule.File) {
+	cfg := getVisConfig(c)
+	if f == nil {
+		return
+	}
+
+	for _, d := range f.Directives {
+		switch d.Key {
+		case _directiveName:
+			for _, target := range strings.Split(d.Value, ",") {
+				cfg.visibilityTargets = append(cfg.visibilityTargets, target)
+			}
+		}
+	}
+	c.Exts[_extName] = cfg
+}
+
+// /Configurator embed

language/bazel/visibility/lang.go

@@ -0,0 +1,55 @@
+package visibility
+
+import (
+	"flag"
+	"strings"
+
+	"github.com/bazelbuild/bazel-gazelle/config"
+	"github.com/bazelbuild/bazel-gazelle/language"
+	"github.com/bazelbuild/bazel-gazelle/rule"
+)
+
+type visibilityExtension struct{}
+
+// NewLanguage constructs a new language.Language modifying visibility.
+func NewLanguage() language.Language {
+	return &visibilityExtension{}
+}
+
+// Kinds instructs gazelle to match any 'package' rule as BUILD files can only have one.
+func (*visibilityExtension) Kinds() map[string]rule.KindInfo {
+	return map[string]rule.KindInfo{
+		"package": {
+			MatchAny: true,
+			MergeableAttrs: map[string]bool{
+				"default_visibility": true,
+			},
+		},
+	}
+}
+
+// Loads noops because there are no imports to add
+func (*visibilityExtension) Loads() []rule.LoadInfo {
+	return nil
+}
+
+// GenerateRules does the hard work of setting the default_visibility if a config exists.
+func (*visibilityExtension) GenerateRules(args language.GenerateArgs) language.GenerateResult {
+	res := language.GenerateResult{}
+	cfg := getVisConfig(args.Config)
+
+	if len(cfg.visibilityTargets) == 0 {
+		return res
+	}
+
+	r := rule.NewRule("package", "")
+	r.SetAttr("default_visibility", cfg.visibilityTargets)
+
+	res.Gen = append(res.Gen, r)
+	// we have to add a nil to Imports because there is length-matching validation with Gen.
+	res.Imports = append(res.Imports, nil)
+	return res
+}
+
+// Fix noop because there is nothing out there to fix yet
+func (*visibilityExtension) Fix(c *config.Config, f *rule.File) {}

language/bazel/visibility/lang_test.go

@@ -0,0 +1,74 @@
+package visibility_test
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/bazelbuild/bazel-gazelle/language/bazel/visibility"
+	"github.com/bazelbuild/bazel-gazelle/config"
+	"github.com/bazelbuild/bazel-gazelle/label"
+	"github.com/bazelbuild/bazel-gazelle/language"
+	"github.com/bazelbuild/bazel-gazelle/rule"
+	"github.com/stretchr/testify/require"
+)
+
+func TestNoopsBecauseILoveCoverage(t *testing.T) {
+	ext := visibility.NewLanguage()
+
+	ext.RegisterFlags(nil /* flagset */, "command", nil /* config */)
+	ext.Resolve(nil /* config */, nil /* RuleIndex */, nil /* RemoteCache */, nil /* Rule */, nil /* imports */, label.New("repo", "pkg", "name"))
+	ext.Fix(nil /* config */, nil /* File */)
+	require.Nil(t, ext.CheckFlags(nil /* flagset */, nil /* config */))
+	require.Nil(t, ext.Imports(nil /* rule */, nil /* rule */, nil /* file */))
+	require.Nil(t, ext.Embeds(nil /* rule */, label.New("repo", "pkg", "name")))
+	require.Nil(t, ext.Loads())
+	require.NotNil(t, ext.KnownDirectives())
+	require.NotNil(t, ext.Name())
+}
+
+func Test_NoDirective(t *testing.T) {
+	cfg := config.New()
+	file := rule.EmptyFile("path", "pkg")
+
+	ext := visibility.NewLanguage()
+	ext.Configure(cfg, "rel", file)
+	res := ext.GenerateRules(language.GenerateArgs{Config: cfg})
+
+	require.Len(t, res.Imports, 0)
+	require.Len(t, res.Gen, 0)
+}
+
+func Test_NewDirective(t *testing.T) {
+	testVis := "//src:__subpackages__"
+	cfg := config.New()
+	file, err := rule.LoadData("path", "pkg", []byte(fmt.Sprintf("# gazelle:default_visibility %s", testVis)))
+	require.Nil(t, err)
+
+	ext := visibility.NewLanguage()
+	ext.Configure(cfg, "rel", file)
+	res := ext.GenerateRules(language.GenerateArgs{Config: cfg})
+
+	require.Len(t, res.Gen, 1)
+	require.Len(t, res.Imports, 1)
+	require.Len(t, res.Gen[0].AttrStrings("default_visibility"), 1)
+	require.Equal(t, testVis, res.Gen[0].AttrStrings("default_visibility")[0])
+}
+
+func Test_ReplacementDirective(t *testing.T) {
+	testVis := "//src:__subpackages__"
+	cfg := config.New()
+	file, err := rule.LoadData("path", "pkg", []byte(fmt.Sprintf(`
+# gazelle:default_visibility %s
+
+package(default_visibility = "//not-src:__subpackages__")
+`, testVis)))
+	require.Nil(t, err)
+
+	ext := visibility.NewLanguage()
+	ext.Configure(cfg, "rel", file)
+	res := ext.GenerateRules(language.GenerateArgs{Config: cfg})
+
+	require.Len(t, res.Gen, 1)
+	require.Len(t, res.Imports, 1)
+	require.Len(t, res.Gen[0].AttrStrings("default_visibility"), 1)
+	require.Equal(t, testVis, res.Gen[0].AttrStrings("default_visibility")[0])

language/bazel/visibility/resolve.go

@@ -0,0 +1,35 @@
+package visibility
+
+import (
+	"flag"
+	"strings"
+
+	"github.com/bazelbuild/bazel-gazelle/config"
+	"github.com/bazelbuild/bazel-gazelle/label"
+	"github.com/bazelbuild/bazel-gazelle/repo"
+	"github.com/bazelbuild/bazel-gazelle/resolve"
+	"github.com/bazelbuild/bazel-gazelle/rule"
+)
+
+const (
+	_extName = "visibility_extension"
+)
+
+// Name returns the extension name.
+func (*visibilityExtension) Name() string {
+	return _extName
+}
+
+// Imports noops because no imports are needed to leverage this functionality.
+func (*visibilityExtension) Imports(c *config.Config, r *rule.Rule, f *rule.File) []resolve.ImportSpec {
+	return nil
+}
+
+// Embeds noops because we are not a traditional rule, and cannot be embedded.
+func (*visibilityExtension) Embeds(r *rule.Rule, from label.Label) []label.Label {
+	return nil
+}
+
+// Resolve noops because we don't have deps=[] to resolve.
+func (*visibilityExtension) Resolve(c *config.Config, ix *resolve.RuleIndex, rc *repo.RemoteCache, r *rule.Rule, imports interface{}, from label.Label) {
+}