tools: Extract getDawnRoot() from run-cts to utils

This is needed elsewhere.
Rename location.go to paths.go, as this is really dealing with file
paths.

Bug: dawn:1342
Change-Id: Ifdbfafc0fd763ac7ec2b8f692efc35772c4793da
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/87704
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>

tools/src/utils/location.go

@@ -1,39 +0,0 @@
-// Copyright 2022 The Tint Authors.
-//
-// 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 utils
-
-import (
-	"fmt"
-	"path/filepath"
-	"runtime"
-)
-
-// ThisLine returns the filepath and line number of the calling function
-func ThisLine() string {
-	_, file, line, ok := runtime.Caller(1)
-	if !ok {
-		return ""
-	}
-	return fmt.Sprintf("%v:%v", file, line)
-}
-
-// ThisDir returns the directory of the caller function
-func ThisDir() string {
-	_, file, _, ok := runtime.Caller(1)
-	if !ok {
-		return ""
-	}
-	return filepath.Dir(file)
-}

tools/src/utils/paths.go

@@ -0,0 +1,77 @@
+// Copyright 2022 The Tint Authors.
+//
+// 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 utils
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+)
+
+// ThisLine returns the filepath and line number of the calling function
+func ThisLine() string {
+	_, file, line, ok := runtime.Caller(1)
+	if !ok {
+		return ""
+	}
+	return fmt.Sprintf("%v:%v", file, line)
+}
+
+// ThisDir returns the directory of the caller function
+func ThisDir() string {
+	_, file, _, ok := runtime.Caller(1)
+	if !ok {
+		return ""
+	}
+	return filepath.Dir(file)
+}
+
+// DawnRoot returns the path to the dawn project's root directory or empty
+// string if not found.
+func DawnRoot() string {
+	return pathOfFileInParentDirs(ThisDir(), "DEPS")
+}
+
+// pathOfFileInParentDirs looks for file with `name` in paths starting from
+// `path`, and up into parent directories, returning the clean path in which the
+// file is found, or empty string if not found.
+func pathOfFileInParentDirs(path string, name string) string {
+	sep := string(filepath.Separator)
+	path, _ = filepath.Abs(path)
+	numDirs := strings.Count(path, sep) + 1
+	for i := 0; i < numDirs; i++ {
+		test := filepath.Join(path, name)
+		if _, err := os.Stat(test); err == nil {
+			return filepath.Clean(path)
+		}
+
+		path = path + sep + ".."
+	}
+	return ""
+}
+
+// ExpandHome returns the string with all occurrences of '~' replaced with the
+// user's home directory. The the user's home directory cannot be found, then
+// the input string is returned.
+func ExpandHome(path string) string {
+	if strings.ContainsRune(path, '~') {
+		if home, err := os.UserHomeDir(); err == nil {
+			return strings.ReplaceAll(path, "~", home)
+		}
+	}
+	return path
+}

tools/src/utils/paths_test.go

@@ -15,15 +15,17 @@
 package utils_test
 
 import (
+	"path/filepath"
 	"strings"
 	"testing"
 
 	"dawn.googlesource.com/dawn/tools/src/utils"
+	"github.com/google/go-cmp/cmp"
 )
 
 func TestThisLine(t *testing.T) {
 	td := utils.ThisLine()
-	if !strings.HasSuffix(td, "location_test.go:25") {
+	if !strings.HasSuffix(td, "paths_test.go:27") {
 		t.Errorf("TestThisLine() returned %v", td)
 	}
 }
@@ -34,3 +36,16 @@ func TestThisDir(t *testing.T) {
 		t.Errorf("ThisDir() returned %v", td)
 	}
 }
+
+func TestDawnRoot(t *testing.T) {
+	dr := utils.DawnRoot()
+	rel, err := filepath.Rel(dr, utils.ThisDir())
+	if err != nil {
+		t.Fatalf("%v", err)
+	}
+	got := filepath.ToSlash(rel)
+	expect := `tools/src/utils`
+	if diff := cmp.Diff(got, expect); diff != "" {
+		t.Errorf("DawnRoot() returned %v.\n%v", dr, diff)
+	}
+}