Handle empty input file case in Metadata generation

Bug: 296873595
Test: Manual test (use go test inside tools/metadata/testdata)

Ignore-AOSP-First: CPing test_spec rule to udc-mainline-prod to support migration of test targets. Cherry pick of: aosp/2835510

Change-Id: Ib48e88bdad4c870be3ca955abfd64ee8dd74f85d
Merged-In: Ib48e88bdad4c870be3ca955abfd64ee8dd74f85d

4 files changed, 44 insertions, 0 deletions

diff --git a/tools/metadata/generator.go b/tools/metadata/generator.go
index eb877553d3..bb8293a032 100644
--- a/tools/metadata/generator.go
+++ b/tools/metadata/generator.go
@@ -73,6 +73,20 @@ func readFileToString(filePath string) string {
 	return string(data)
 }
 
+func writeNewlineToOutputFile(outputFile string) {
+	file, err := os.Create(outputFile)
+	data := "\n"
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer file.Close()
+
+	_, err = file.Write([]byte(data))
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
 func processTestSpecProtobuf(
 	filePath string, ownershipMetadataMap *sync.Map, keyLocks *keyToLocksMap,
 	errCh chan error, wg *sync.WaitGroup,
@@ -140,6 +154,10 @@ func main() {
 
 	inputFileData := strings.TrimRight(readFileToString(*inputFile), "\n")
 	filePaths := strings.Split(inputFileData, "\n")
+	if len(filePaths) == 1 && filePaths[0] == "" {
+		writeNewlineToOutputFile(*outputFile)
+		return
+	}
 	ownershipMetadataMap := &sync.Map{}
 	keyLocks := &keyToLocksMap{}
 	errCh := make(chan error, len(filePaths))
diff --git a/tools/metadata/testdata/emptyInputFile.txt b/tools/metadata/testdata/emptyInputFile.txt
new file mode 100644
index 0000000000..8b13789179
--- /dev/null
+++ b/tools/metadata/testdata/emptyInputFile.txt
@@ -0,0 +1 @@
+
diff --git a/tools/metadata/testdata/generatedEmptyOutputFile.txt b/tools/metadata/testdata/generatedEmptyOutputFile.txt
new file mode 100644
index 0000000000..8b13789179
--- /dev/null
+++ b/tools/metadata/testdata/generatedEmptyOutputFile.txt
@@ -0,0 +1 @@
+
diff --git a/tools/metadata/testdata/metadata_test.go b/tools/metadata/testdata/metadata_test.go
index 03c4f29ab2..71856fe606 100644
--- a/tools/metadata/testdata/metadata_test.go
+++ b/tools/metadata/testdata/metadata_test.go
@@ -63,3 +63,27 @@ func TestMetadataNegativeCase(t *testing.T) {
 		)
 	}
 }
+
+func TestEmptyInputFile(t *testing.T) {
+	cmd := exec.Command(
+		"metadata", "-rule", "test_spec", "-inputFile", "./emptyInputFile.txt", "-outputFile",
+		"./generatedEmptyOutputFile.txt",
+	)
+	stderr, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("Error running metadata command: %s. Error: %v", stderr, err)
+	}
+
+	// Read the contents of the generated output file
+	generatedOutput, err := ioutil.ReadFile("./generatedEmptyOutputFile.txt")
+	if err != nil {
+		t.Fatalf("Error reading generated output file: %s", err)
+	}
+
+	fmt.Println()
+
+	// Compare the contents
+	if string(generatedOutput) != "\n" {
+		t.Errorf("Generated file contents do not match the expected output")
+	}
+}