Add per-file mode for proto_library generation (bazel-contrib#1033)

* Add per-file mode for proto_library generation

CONTRIBUTING.md

@@ -29,7 +29,7 @@ the one above, the
    add [tests](https://github.com/bazelbuild/bazel-gazelle/tree/master/tests). 
    Run the existing tests with `bazel test //...`. Update
    [README.rst](https://github.com/bazelbuild/bazel-gazelle/blob/master/README.rst)
-   if appropriate. 
+   if appropriate.
 1. [Create a pull request](https://help.github.com/articles/creating-a-pull-request/).
    This will start the code review process. **All submissions, including
    submissions by project members, require review.**

language/proto/config.go

@@ -97,6 +97,9 @@ const (
 	// PackageMode generates a proto_library for each set of .proto files with
 	// the same package name in each directory.
 	PackageMode
+
+	// FileMode generates a proto_library for each .proto file.
+	FileMode
 )
 
 func ModeFromString(s string) (Mode, error) {
@@ -111,6 +114,8 @@ func ModeFromString(s string) (Mode, error) {
 		return LegacyMode, nil
 	case "package":
 		return PackageMode, nil
+	case "file":
+		return FileMode, nil
 	default:
 		return 0, fmt.Errorf("unrecognized proto mode: %q", s)
 	}
@@ -128,6 +133,8 @@ func (m Mode) String() string {
 		return "legacy"
 	case PackageMode:
 		return "package"
+	case FileMode:
+		return "file"
 	default:
 		log.Panicf("unknown mode %d", m)
 		return ""

language/proto/generate.go

@@ -119,18 +119,25 @@ func buildPackages(pc *ProtoConfig, dir, rel string, protoFiles, genFiles []stri
 	for _, name := range protoFiles {
 		info := protoFileInfo(dir, name)
 		key := info.PackageName
-		if pc.groupOption != "" {
+
+		if pc.Mode == FileMode {
+			key = strings.TrimSuffix(name, ".proto")
+		} else if pc.groupOption != "" { // implicitly PackageMode
 			for _, opt := range info.Options {
 				if opt.Key == pc.groupOption {
 					key = opt.Value
 					break
 				}
 			}
 		}
+
 		if packageMap[key] == nil {
 			packageMap[key] = newPackage(info.PackageName)
 		}
 		packageMap[key].addFile(info)
+		if key != info.PackageName {
+			packageMap[key].RuleName = key
+		}
 	}
 
 	switch pc.Mode {
@@ -147,7 +154,7 @@ func buildPackages(pc *ProtoConfig, dir, rel string, protoFiles, genFiles []stri
 		}
 		return []*Package{pkg}
 
-	case PackageMode:
+	case PackageMode, FileMode:
 		pkgs := make([]*Package, 0, len(packageMap))
 		for _, pkg := range packageMap {
 			pkgs = append(pkgs, pkg)
@@ -212,7 +219,7 @@ func generateProto(pc *ProtoConfig, rel string, pkg *Package, shouldSetVisibilit
 	if pc.Mode == DefaultMode {
 		name = RuleName(goPackageName(pkg), pc.GoPrefix, rel)
 	} else {
-		name = RuleName(pkg.Options[pc.groupOption], pkg.Name, rel)
+		name = RuleName(pkg.RuleName, pkg.Name, rel)
 	}
 	r := rule.NewRule("proto_library", name)
 	srcs := make([]string, 0, len(pkg.Files))

language/proto/package.go

@@ -21,6 +21,7 @@ import "path/filepath"
 // same package name. This translates to a proto_library rule.
 type Package struct {
 	Name        string
+	RuleName    string // if not set, defaults to Name
 	Files       map[string]FileInfo
 	Imports     map[string]bool
 	Options     map[string]string

language/proto/resolve_test.go

@@ -350,6 +350,41 @@ proto_library(
     name = "dep_proto",
     deps = ["//foo:foo_proto"],
 )
+`,
+		}, {
+			desc: "test single file resolution in file mode",
+			index: []buildFile{{
+				rel: "somedir",
+				content: `
+# gazelle:proto file
+
+proto_library(
+    name = "foo_proto",
+    srcs = ["foo.proto"],
+)
+
+proto_library(
+    name = "bar_proto",
+    srcs = ["bar.proto"],
+)
+
+proto_library(
+    name = "baz_proto",
+    srcs = ["baz.proto"],
+)
+`,
+			}},
+			old: `
+proto_library(
+    name = "other_proto",
+    _imports = ["somedir/bar.proto"],
+)
+`,
+			want: `
+proto_library(
+    name = "other_proto",
+    deps = ["//somedir:bar_proto"],
+)
 `,
 		},
 	} {

language/proto/testdata/file_mode/BUILD.old

@@ -0,0 +1 @@
+# gazelle:proto file

language/proto/testdata/file_mode/BUILD.want

@@ -0,0 +1,13 @@
+load("@rules_proto//proto:defs.bzl", "proto_library")
+
+proto_library(
+    name = "bar_proto",
+    srcs = ["bar.proto"],
+    visibility = ["//visibility:public"],
+)
+
+proto_library(
+    name = "foo_proto",
+    srcs = ["foo.proto"],
+    visibility = ["//visibility:public"],
+)

language/proto/testdata/file_mode/bar.proto

@@ -0,0 +1,3 @@
+syntax = "proto3";
+
+package file_mode;

language/proto/testdata/file_mode/foo.proto

@@ -0,0 +1,3 @@
+syntax = "proto3";
+
+package file_mode;