do not generate an empty rule if a go_proto_library was already gener… (

bazel-contrib#1927)

**What type of PR is this?**
> Bug fix

**What package or component does this PR mostly affect?**

> language/go

**What does this PR do? Why is it needed?**

Prevents overwriting of a generated `go_proto_library` in the case where
the package name matches the proto file name. See issue for more
details.

**Which issues(s) does this PR fix?**
Fixes bazel-contrib#1926

**Other notes for review**
Unclear exactly how to write a test for it, but did local testing at
least.

language/go/generate.go

@@ -329,11 +329,36 @@ func (gl *goLang) GenerateRules(args language.GenerateArgs) language.GenerateRes
 			}
 		}
 
+		var genGoProtoRules []string
+		for _, r := range rules {
+			if r.Kind() == "go_proto_library" {
+				genGoProtoRules = append(genGoProtoRules, r.Name())
+			}
+		}
+
 		// Generate Go rules.
 		if protoName == "" {
 			// Empty proto rules for deletion.
 			_, rs := g.generateProto(pcMode, []protoTarget{pkg.proto}, pkg.importPath)
-			rules = append(rules, rs...)
+
+			// Do not generate empty rule if already created above
+			found := false
+			for _, r := range rs {
+				if r.Kind() == "go_proto_library" {
+					for _, pr := range genGoProtoRules {
+						if pr == r.Name() {
+							found = true
+							break
+						}
+					}
+					if found {
+						break
+					}
+				}
+			}
+			if !found {
+				rules = append(rules, rs...)
+			}
 		}
 		lib := g.generateLib(pkg, protoEmbeds)
 		var libName string

tests/BUILD.bazel

@@ -35,6 +35,15 @@ gazelle_binary(
     visibility = ["//visibility:private"],
 )
 
+gazelle_binary(
+    name = "gazelle_with_proto_and_go_languages",
+    languages = [
+        "//language/proto:go_default_library",
+        "//language/go:go_default_library",
+    ],
+    visibility = ["//visibility:private"],
+)
+
 [gazelle_generation_test(
     # Name the test the path to the directory containing the WORKSPACE file.
     name = file[0:-len("/WORKSPACE")],

tests/fix_package_proto_name_match/BUILD.in

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

tests/fix_package_proto_name_match/BUILD.out

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

tests/fix_package_proto_name_match/README.md

@@ -0,0 +1,3 @@
+# Fix go_proto_library dependencies
+
+Fix go_proto_library dependencies when package and proto name match

tests/fix_package_proto_name_match/example/BUILD.out

@@ -0,0 +1,32 @@
+load("@io_bazel_rules_go//proto:def.bzl", "go_proto_library")
+load("@rules_proto//proto:defs.bzl", "proto_library")
+
+proto_library(
+    name = "example_proto",
+    srcs = ["example.proto"],
+    visibility = ["//visibility:public"],
+    deps = ["//google/type:type_proto"],
+)
+
+proto_library(
+    name = "other_proto",
+    srcs = ["other.proto"],
+    visibility = ["//visibility:public"],
+    deps = ["//google/type:type_proto"],
+)
+
+go_proto_library(
+    name = "example_go_proto",
+    importpath = "github.com/bazelbuild/bazel-gazelle/fix_package_proto_name_match/example/example",
+    proto = ":example_proto",
+    visibility = ["//visibility:public"],
+    deps = ["//google/type:date_proto"],
+)
+
+go_proto_library(
+    name = "other_go_proto",
+    importpath = "github.com/bazelbuild/bazel-gazelle/fix_package_proto_name_match/example/other",
+    proto = ":other_proto",
+    visibility = ["//visibility:public"],
+    deps = ["//google/type:date_proto"],
+)

tests/fix_package_proto_name_match/example/example.proto

@@ -0,0 +1,12 @@
+
+syntax = "proto3";
+
+package proto.example.example;
+
+option go_package = "github.com/bazelbuild/bazel-gazelle/fix_package_proto_name_match/example/example";
+
+import "google/type/date.proto";
+
+message Example {
+  google.type.Date date = 1;
+}

tests/fix_package_proto_name_match/example/other.proto

@@ -0,0 +1,11 @@
+syntax = "proto3";
+
+package proto.example.other;
+
+option go_package = "github.com/bazelbuild/bazel-gazelle/fix_package_proto_name_match/example/other";
+
+import "google/type/date.proto";
+
+message Other {
+  google.type.Date date = 1;
+}

tests/tools.bzl

@@ -20,4 +20,7 @@ def get_binary(target):
     if "loads_from_flag" in target:
         return ":gazelle_with_language_loads_from_flag"
 
+    if "fix_package_proto_name_match" in target:
+        return ":gazelle_with_proto_and_go_languages"
+
     return ":gazelle"