Add test ensuring that pre-existing targets are kept intact when they violate the naming convention, and adjust behaviour to match

Author: shaldengeki

gazelle/README.md

@@ -266,7 +266,7 @@ py_libary(
 
 #### Directive: `python_proto_naming_convention`:
 
-Set this directive to a string pattern to control how the generated `py_proto_library` targets are named. Gazelle will replace `$proto_name$` in the pattern with the name of the `proto_library` rule, stripping out a trailing `_proto`. For example:
+Set this directive to a string pattern to control how the generated `py_proto_library` targets are named. When generating new `py_proto_library` rules, Gazelle will replace `$proto_name$` in the pattern with the name of the `proto_library` rule, stripping out a trailing `_proto`. For example:
 
 ```starlark
 # gazelle:python_generate_proto true
@@ -286,7 +286,7 @@ py_proto_library(
 )
 ```
 
-The default naming convention is `$proto_name$_pb2_py`, so by default in the above example Gazelle would generate `foo_pb2_py`.
+The default naming convention is `$proto_name$_pb2_py`, so by default in the above example Gazelle would generate `foo_pb2_py`. Any pre-existing rules are left in place and not renamed.
 
 Note that the Python library will always be imported as `foo_pb2` in Python code, regardless of the naming convention. Also note that Gazelle is currently not able to map said imports, e.g. `import foo_pb2`, to fill in `py_proto_library` targets as dependencies of other rules. See [this issue](https://github.com/bazel-contrib/rules_python/issues/1703).
 

gazelle/python/generate.go

@@ -582,10 +582,16 @@ func generateProtoLibraries(args language.GenerateArgs, cfg *pythonconfig.Config
 
 	// Next, enumerate all the pre-existing py_proto_library in this package, so we can delete unnecessary rules later.
 	pyProtoRules := map[string]bool{}
+	pyProtoRulesForProto := map[string]string{}
 	if args.File != nil {
 		for _, r := range args.File.Rules {
 			if r.Kind() == "py_proto_library" {
 				pyProtoRules[r.Name()] = false
+
+				protos := r.AttrStrings("deps")
+				for _, proto := range protos {
+					pyProtoRulesForProto[strings.TrimPrefix(proto, ":")] = r.Name()
+				}
 			}
 		}
 	}
@@ -594,6 +600,11 @@ func generateProtoLibraries(args language.GenerateArgs, cfg *pythonconfig.Config
 	// Generate a py_proto_library for each proto_library.
 	for _, protoRuleName := range protoRuleNames {
 		pyProtoLibraryName := cfg.RenderProtoName(protoRuleName)
+		if ruleName, ok := pyProtoRulesForProto[protoRuleName]; ok {
+			// There exists a pre-existing py_proto_library for this proto. Keep this name.
+			pyProtoLibraryName = ruleName
+		}
+
 		pyProtoLibrary := newTargetBuilder(pyProtoLibraryKind, pyProtoLibraryName, pythonProjectRoot, args.Rel, &emptySiblings).
 			addVisibility(visibility).
 			addResolvedDependency(":" + protoRuleName).

gazelle/python/testdata/directive_python_proto_naming_convention/README.md

@@ -6,3 +6,4 @@ correctly:
 1.  Has no effect on pre-existing `py_proto_library` when `gazelle:python_generate_proto` is disabled.
 2.  Uses the default value when proto generation is on and `python_proto_naming_convention` is not set.
 3.  Uses the provided naming convention when proto generation is on and `python_proto_naming_convention` is set.
+4.  With a pre-existing `py_proto_library` not following a given naming convention, keeps it intact and does not rename it.

gazelle/python/testdata/directive_python_proto_naming_convention/test4_python_generation_enabled_with_preexisting_keeps_intact/BUILD.in

@@ -0,0 +1,16 @@
+load("@rules_proto//proto:defs.bzl", "proto_library")
+
+# gazelle:python_generate_proto true
+# gazelle:python_proto_naming_convention $proto_name$_bar
+
+proto_library(
+    name = "foo_proto",
+    srcs = ["foo.proto"],
+    visibility = ["//:__subpackages__"],
+)
+
+py_proto_library(
+    name = "foo_py_proto",
+    visibility = ["//:__subpackages__"],
+    deps = [":foo_proto"],
+)

gazelle/python/testdata/directive_python_proto_naming_convention/test4_python_generation_enabled_with_preexisting_keeps_intact/BUILD.out

@@ -0,0 +1,17 @@
+load("@com_google_protobuf//bazel:py_proto_library.bzl", "py_proto_library")
+load("@rules_proto//proto:defs.bzl", "proto_library")
+
+# gazelle:python_generate_proto true
+# gazelle:python_proto_naming_convention $proto_name$_bar
+
+proto_library(
+    name = "foo_proto",
+    srcs = ["foo.proto"],
+    visibility = ["//:__subpackages__"],
+)
+
+py_proto_library(
+    name = "foo_py_proto",
+    visibility = ["//:__subpackages__"],
+    deps = [":foo_proto"],
+)

gazelle/python/testdata/directive_python_proto_naming_convention/test4_python_generation_enabled_with_preexisting_keeps_intact/foo.proto

@@ -0,0 +1,7 @@
+syntax = "proto3";
+
+package foo;
+
+message Foo {
+    string bar = 1;
+}