From 0baf2db4a456c7dea47d649afff8031556325951 Mon Sep 17 00:00:00 2001
From: Benjamin Peterson <benjamin@python.org>
Date: Thu, 15 Nov 2018 04:43:25 -0800
Subject: [PATCH] Expand the set of file names considered to be build files.
 (#400)

When using Bazel external workspaces, it's common to have files named like something.BUILD or BUILD.something, which become the BUILD file for the @something repository. This CL modifies build.ParseDefault so that it considers any filename with an extension or base called "BUILD" to be a BUILD file. While workspace file naming in the wild is less creative, I didn't see a reason not to extend the same rule to workspace files.
---
 build/BUILD.bazel |  2 ++
 build/lex.go      | 21 +++++++++++++++------
 build/lex_test.go | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 63 insertions(+), 6 deletions(-)
 create mode 100644 build/lex_test.go

diff --git a/build/BUILD.bazel b/build/BUILD.bazel
index ca70fb11d..945288a8e 100644
--- a/build/BUILD.bazel
+++ b/build/BUILD.bazel
@@ -29,6 +29,7 @@ go_test(
     size = "small",
     srcs = [
         "checkfile_test.go",
+        "lex_test.go",
         "parse_test.go",
         "print_test.go",
         "quote_test.go",
@@ -44,6 +45,7 @@ go_test(
     ],
     embed = [":go_default_library"],
     deps = [
+        "//tables:go_default_library",
         "//testutils",
     ],
 )
diff --git a/build/lex.go b/build/lex.go
index 61b0b79c6..f698e2667 100644
--- a/build/lex.go
+++ b/build/lex.go
@@ -28,11 +28,7 @@ import (
 
 // BuildFilenames is a collection of filenames in lowercase that are treated as BUILD files.
 var BuildFilenames = map[string]bool{
-	"build":           true,
-	"build.bazel":     true,
-	"workspace":       true,
-	"workspace.bazel": true,
-	"stdin":           true,
+	"stdin": true,
 }
 
 // ParseBuild parses a file, marks it as a BUILD file and returns the corresponding parse tree.
@@ -59,13 +55,26 @@ func ParseDefault(filename string, data []byte) (*File, error) {
 	return f, err
 }
 
+func isBuildFilename(basename string) bool {
+	basename = strings.ToLower(basename)
+	if isBuild, ok := BuildFilenames[basename]; ok {
+		return isBuild
+	}
+	ext := filepath.Ext(basename)
+	if ext == ".bzl" || ext == ".sky" {
+		return false
+	}
+	base := basename[:len(basename)-len(ext)]
+	return ext == ".build" || ext == ".workspace" || base == "build" || base == "workspace"
+}
+
 // Parse parses the input data and returns the corresponding parse tree.
 //
 // Uses the filename to detect the formatting type (either build or default) and calls
 // either ParseBuild or to ParseDefault correspondingly.
 func Parse(filename string, data []byte) (*File, error) {
 	basename := filepath.Base(filename)
-	if BuildFilenames[strings.ToLower(basename)] {
+	if isBuildFilename(basename) {
 		return ParseBuild(filename, data)
 	}
 	return ParseDefault(filename, data)
diff --git a/build/lex_test.go b/build/lex_test.go
new file mode 100644
index 000000000..801bbf6de
--- /dev/null
+++ b/build/lex_test.go
@@ -0,0 +1,46 @@
+/*
+Copyright 2018 Bazel contributors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+*/
+
+package build
+
+import (
+	"testing"
+)
+
+func TestIsBuildFilename(t *testing.T) {
+	cases := map[string]bool{
+		"BUILD":           true,
+		"build":           true,
+		"bUIld":           true,
+		"BUILD.bazel":     true,
+		"build.bzl":       false,
+		"build.sky":       false,
+		"WORKSPACE":       true,
+		"external.BUILD":  true,
+		"BUILD.external":  true,
+		"aBUILD":          false,
+		"thing.sky":       false,
+		"my.WORKSPACE":    true,
+		"thing.bzl":       false,
+		"workspace.bazel": true,
+	}
+	for name, isBuild := range cases {
+		res := isBuildFilename(name)
+		if res != isBuild {
+			t.Errorf("isBuildFilename(%q) should be %v but was %v", name, isBuild, res)
+		}
+	}
+}