perf(gazelle): cache fs check for BUILD files (#3951)

GitOrigin-RevId: f2e0e86c9d5b5a9ceceb9451ef4a6fab97f7de35

gazelle/common/bazel.go

@@ -8,17 +8,27 @@ import (
 var (
 	// BUILD file names.
 	buildFileNames = []string{"BUILD", "BUILD.bazel"}
+
+	// A set of already-seen Bazel packages so we avoid doing
+	// disk IO over and over to determine if a directory is a Bazel package.
+	isPackageCache = make(map[string]bool)
 )
 
 // IsBazelPackage determines if the directory is a Bazel package by probing for
 // the existence of a known BUILD file name.
 func IsBazelPackage(dir string) bool {
+	if isPkg, cached := isPackageCache[dir]; cached {
+		return isPkg
+	}
+
 	for _, buildFilename := range buildFileNames {
 		buildPath := path.Join(dir, buildFilename)
 		if _, err := os.Stat(buildPath); err == nil {
+			isPackageCache[dir] = true
 			return true
 		}
 	}
+	isPackageCache[dir] = false
 	return false
 }