refactor(gazelle): Move plugin to a separate directory.

This is in order to make bazelbuild#972 easier to review. This PR is only moving
files and addressing a few small review comments made in the initial
review of bazelbuild#972.

Work towards bazelbuild#965.

gazelle/BUILD.bazel

@@ -1,76 +1,12 @@
-load("@bazel_gazelle//:def.bzl", "gazelle_binary")
-load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
-load("@rules_python//python:defs.bzl", "py_binary")
-
-go_library(
+alias(
     name = "gazelle",
-    srcs = [
-        "configure.go",
-        "fix.go",
-        "generate.go",
-        "kinds.go",
-        "language.go",
-        "parser.go",
-        "resolve.go",
-        "std_modules.go",
-        "target.go",
-    ],
-    data = [
-        ":parse",
-        ":std_modules",
-    ],
-    importpath = "github.com/bazelbuild/rules_python/gazelle",
-    visibility = ["//visibility:public"],
-    deps = [
-        "//gazelle/manifest",
-        "//gazelle/pythonconfig",
-        "@bazel_gazelle//config:go_default_library",
-        "@bazel_gazelle//label:go_default_library",
-        "@bazel_gazelle//language:go_default_library",
-        "@bazel_gazelle//repo:go_default_library",
-        "@bazel_gazelle//resolve:go_default_library",
-        "@bazel_gazelle//rule:go_default_library",
-        "@com_github_bazelbuild_buildtools//build:go_default_library",
-        "@com_github_bmatcuk_doublestar//:doublestar",
-        "@com_github_emirpasic_gods//lists/singlylinkedlist",
-        "@com_github_emirpasic_gods//sets/treeset",
-        "@com_github_emirpasic_gods//utils",
-        "@com_github_google_uuid//:uuid",
-        "@io_bazel_rules_go//go/tools/bazel:go_default_library",
-    ],
-)
-
-py_binary(
-    name = "parse",
-    srcs = ["parse.py"],
+    actual = "//gazelle/python",
     visibility = ["//visibility:public"],
 )
 
-py_binary(
-    name = "std_modules",
-    srcs = ["std_modules.py"],
-    visibility = ["//visibility:public"],
-)
-
-go_test(
-    name = "gazelle_test",
-    srcs = ["python_test.go"],
-    data = [
-        ":gazelle_python_binary",
-        ":parse",
-        ":std_modules",
-    ] + glob(["testdata/**"]),
-    deps = [
-        "@bazel_gazelle//testtools:go_default_library",
-        "@com_github_emirpasic_gods//lists/singlylinkedlist",
-        "@com_github_ghodss_yaml//:yaml",
-        "@io_bazel_rules_go//go/tools/bazel:go_default_library",
-    ],
-)
-
-gazelle_binary(
+alias(
     name = "gazelle_python_binary",
-    languages = ["//gazelle"],
+    actual = "//gazelle/python:gazelle_binary",
     visibility = ["//visibility:public"],
 )
 
@@ -79,6 +15,7 @@ filegroup(
     srcs = glob(["**"]) + [
         "//gazelle/manifest:distribution",
         "//gazelle/modules_mapping:distribution",
+        "//gazelle/python:distribution",
         "//gazelle/pythonconfig:distribution",
     ],
     visibility = ["//:__pkg__"],

gazelle/def.bzl

@@ -2,6 +2,6 @@
 """
 
 GAZELLE_PYTHON_RUNTIME_DEPS = [
-    "@rules_python//gazelle:parse",
-    "@rules_python//gazelle:std_modules",
+    "@rules_python//gazelle/python:parse",
+    "@rules_python//gazelle/python:std_modules",
 ]

gazelle/python/BUILD.bazel

@@ -0,0 +1,81 @@
+load("@bazel_gazelle//:def.bzl", "gazelle_binary")
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
+load("@rules_python//python:defs.bzl", "py_binary")
+
+go_library(
+    name = "python",
+    srcs = [
+        "configure.go",
+        "fix.go",
+        "generate.go",
+        "kinds.go",
+        "language.go",
+        "parser.go",
+        "resolve.go",
+        "std_modules.go",
+        "target.go",
+    ],
+    data = [
+        ":parse",
+        ":std_modules",
+    ],
+    importpath = "github.com/bazelbuild/rules_python/gazelle/python",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//gazelle/manifest",
+        "//gazelle/pythonconfig",
+        "@bazel_gazelle//config:go_default_library",
+        "@bazel_gazelle//label:go_default_library",
+        "@bazel_gazelle//language:go_default_library",
+        "@bazel_gazelle//repo:go_default_library",
+        "@bazel_gazelle//resolve:go_default_library",
+        "@bazel_gazelle//rule:go_default_library",
+        "@com_github_bazelbuild_buildtools//build:go_default_library",
+        "@com_github_bmatcuk_doublestar//:doublestar",
+        "@com_github_emirpasic_gods//lists/singlylinkedlist",
+        "@com_github_emirpasic_gods//sets/treeset",
+        "@com_github_emirpasic_gods//utils",
+        "@com_github_google_uuid//:uuid",
+        "@io_bazel_rules_go//go/tools/bazel:go_default_library",
+    ],
+)
+
+py_binary(
+    name = "parse",
+    srcs = ["parse.py"],
+    visibility = ["//visibility:public"],
+)
+
+py_binary(
+    name = "std_modules",
+    srcs = ["std_modules.py"],
+    visibility = ["//visibility:public"],
+)
+
+go_test(
+    name = "python_test",
+    srcs = ["python_test.go"],
+    data = [
+        ":gazelle_binary",
+        ":parse",
+        ":std_modules",
+    ] + glob(["testdata/**"]),
+    deps = [
+        "@bazel_gazelle//testtools:go_default_library",
+        "@com_github_emirpasic_gods//lists/singlylinkedlist",
+        "@com_github_ghodss_yaml//:yaml",
+        "@io_bazel_rules_go//go/tools/bazel:go_default_library",
+    ],
+)
+
+gazelle_binary(
+    name = "gazelle_binary",
+    languages = [":python"],
+    visibility = ["//visibility:public"],
+)
+
+filegroup(
+    name = "distribution",
+    srcs = glob(["**"]),
+    visibility = ["//gazelle:__pkg__"],
+)

gazelle/parser.go → gazelle/python/parser.go

@@ -25,7 +25,7 @@ var (
 )
 
 func init() {
-	parseScriptRunfile, err := bazel.Runfile("gazelle/parse")
+	parseScriptRunfile, err := bazel.Runfile("gazelle/python/parse")
 	if err != nil {
 		log.Printf("failed to initialize parser: %v\n", err)
 		os.Exit(1)

gazelle/python_test.go → gazelle/python/python_test.go

@@ -38,9 +38,9 @@ import (
 )
 
 const (
-	extensionDir      = "gazelle/"
-	testDataPath      = extensionDir + "testdata/"
-	gazelleBinaryName = "gazelle_python_binary"
+	extensionDir      = "gazelle" + string(os.PathSeparator) + "python" + string(os.PathSeparator)
+	testDataPath      = extensionDir + "testdata" + string(os.PathSeparator)
+	gazelleBinaryName = "gazelle_binary"
 )
 
 var gazellePath = mustFindGazelle()
@@ -55,7 +55,7 @@ func TestGazelleBinary(t *testing.T) {
 	for _, f := range runfiles {
 		if strings.HasPrefix(f.ShortPath, testDataPath) {
 			relativePath := strings.TrimPrefix(f.ShortPath, testDataPath)
-			parts := strings.SplitN(relativePath, "/", 2)
+			parts := strings.SplitN(relativePath, string(os.PathSeparator), 2)
 			if len(parts) < 2 {
 				// This file is not a part of a testcase since it must be in a dir that
 				// is the test case and then have a path inside of that.
@@ -82,7 +82,7 @@ func testPath(t *testing.T, name string, files []bazel.RunfileEntry) {
 		var config *testYAML
 		for _, f := range files {
 			path := f.Path
-			trim := testDataPath + name + "/"
+			trim := filepath.Join(testDataPath, name) + string(os.PathSeparator)
 			shortPath := strings.TrimPrefix(f.ShortPath, trim)
 			info, err := os.Stat(path)
 			if err != nil {

gazelle/std_modules.go → gazelle/python/std_modules.go

@@ -26,7 +26,7 @@ var (
 func init() {
 	stdModulesSeen = make(map[string]struct{})
 
-	stdModulesScriptRunfile, err := bazel.Runfile("gazelle/std_modules")
+	stdModulesScriptRunfile, err := bazel.Runfile("gazelle/python/std_modules")
 	if err != nil {
 		log.Printf("failed to initialize std_modules: %v\n", err)
 		os.Exit(1)