Move bzl ext (#265)

* Move Gazelle extension to //gazelle/bzl and change package name

This fixes an issue with importing bazel-skylib into
google3. Currently, Glaze (internal Go build file generator) attempts
to generate a target (//gazelle:gazelle) that conflicts with one
that's already declared here.

I think the right solution is actually to move the package into a
subdirectory. In the future (bazelbuild/bazel-gazelle#5), Gazelle's Go
extension will generate target names similar to what Glaze does, so
the same conflict will happen in open source. I think it's also
logical to have a directory of packages in case more need to be added
in the future, and for the extension to have a package name matching
the language it works with.

This is an incompatible change, but the //gazelle directory isn't part
of a tagged release yet, so hopefully it won't break anyone.

* fix runfiles access in test

* Fix gazelle package names.

Co-authored-by: Jay Conrod <jayconrod@google.com>

gazelle/bzl/BUILD

@@ -4,7 +4,7 @@ load("@bazel_gazelle//:def.bzl", "gazelle", "gazelle_binary")
 # gazelle:exclude testdata
 
 go_library(
-    name = "go_default_library",
+    name = "bzl",
     srcs = ["gazelle.go"],
     importpath = "github.com/bazelbuild/bazel-skylib/gazelle",
     visibility = ["//visibility:public"],
@@ -21,14 +21,14 @@ go_library(
 )
 
 go_test(
-    name = "go_default_test",
+    name = "bzl_test",
     srcs = ["gazelle_test.go"],
     data = [
         ":gazelle-skylib",
     ] + glob([
         "testdata/**",
     ]),
-    embed = [":go_default_library"],
+    embed = [":bzl"],
     deps = [
         "@bazel_gazelle//testtools:go_default_library",
         "@io_bazel_rules_go//go/tools/bazel:go_default_library",
@@ -39,7 +39,7 @@ go_test(
 # extension and thus only has the skylib language installed.
 gazelle_binary(
     name = "gazelle-skylib",
-    languages = [":go_default_library"],
+    languages = [":bzl"],
     visibility = [
         # Also make the binary available in the root of the repo for use, but
         # not externally.

gazelle/bzl/gazelle.go

@@ -13,7 +13,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-// Package gazelle generates a `bzl_library` target for every `.bzl` file in
+// Package bzl generates a `bzl_library` target for every `.bzl` file in
 // each package.
 //
 // The `bzl_library` rule is provided by
@@ -21,7 +21,7 @@ limitations under the License.
 //
 // This extension is experimental and subject to change. It is not included
 // in the default Gazelle binary.
-package gazelle
+package bzl
 
 import (
 	"flag"

gazelle/bzl/gazelle_test.go

@@ -1,4 +1,4 @@
-package gazelle
+package bzl
 
 /* Copyright 2020 The Bazel Authors. All rights reserved.
 
@@ -29,7 +29,7 @@ import (
 
 var gazellePath = findGazelle()
 
-const testDataPath = "gazelle/testdata/"
+const testDataPath = "gazelle/bzl/testdata/"
 
 // TestGazelleBinary runs a gazelle binary with starlib installed on each
 // directory in `testdata/*`. Please see `testdata/README.md` for more
@@ -54,6 +54,9 @@ func TestGazelleBinary(t *testing.T) {
 			tests[parts[0]] = append(tests[parts[0]], f)
 		}
 	}
+	if len(tests) == 0 {
+		t.Fatal("no tests found")
+	}
 
 	for testName, files := range tests {
 		testPath(t, testName, files)
@@ -132,7 +135,7 @@ func testPath(t *testing.T, name string, files []bazel.RunfileEntry) {
 }
 
 func findGazelle() string {
-	gazellePath, ok := bazel.FindBinary("gazelle", "gazelle-skylib")
+	gazellePath, ok := bazel.FindBinary("gazelle/bzl", "gazelle-skylib")
 	if !ok {
 		panic("could not find gazelle binary")
 	}