Tombstone: fall back to file timestamp on empty pb timestamp

- Allow empty protobuf timestamps to fall back to the file timestamp
- Update _parse_timestamp_string to accept a fallback
- Pass file_timestamp to its callers
- Add tests for empty and whitespace tombstone timestamps
- Adjust imports in bugreport module to include DumpsysADBState
  Tombstone: use file timestamp on empty pb
- skip 0 bytes tombstones and show debug warning

tests/android/test_artifact_tombstones.py

@@ -2,8 +2,8 @@
 # Copyright (c) 2021-2023 The MVT Authors.
 # Use of this software is governed by the MVT License 1.1 that can be found at
 #   https://license.mvt.re/1.1/
-import os
 import datetime
+import os
 
 import pytest
 
@@ -65,3 +65,89 @@ class TestTombstoneCrashArtifact:
         # MVT should output the local time only:
         # So original 2023-04-12 12:32:40.518290770+0200 -> 2023-04-12 12:32:40.000000
         assert tombstone_result.get("timestamp") == "2023-04-12 12:32:40.518290"
+
+    def test_tombstone_pb_empty_timestamp(self):
+        """Test parsing a protobuf tombstone with an empty timestamp."""
+        tombstone_artifact = TombstoneCrashArtifact()
+        artifact_path = "android_data/bugreport_tombstones/tombstone_empty_timestamp.pb"
+        file = get_artifact(artifact_path)
+        with open(file, "rb") as f:
+            data = f.read()
+
+        file_name = os.path.basename(artifact_path)
+        file_timestamp = datetime.datetime(2024, 1, 15, 10, 30, 45, 123456)
+        tombstone_artifact.parse_protobuf(file_name, file_timestamp, data)
+
+        assert len(tombstone_artifact.results) == 1
+        result = tombstone_artifact.results[0]
+
+        # When tombstone has empty timestamp, should use file modification time
+        assert result.get("timestamp") == "2024-01-15 10:30:45.123456"
+        assert result.get("pid") == 12345
+        assert result.get("uid") == 1000
+        assert result.get("signal_info", {}).get("name") == "SIGSEGV"
+
+    def test_tombstone_pb_empty_timestamp_with_threads(self):
+        """Test parsing a protobuf tombstone with empty timestamp and thread info."""
+        tombstone_artifact = TombstoneCrashArtifact()
+        artifact_path = "android_data/bugreport_tombstones/tombstone_empty_timestamp_with_threads.pb"
+        file = get_artifact(artifact_path)
+        with open(file, "rb") as f:
+            data = f.read()
+
+        file_name = os.path.basename(artifact_path)
+        file_timestamp = datetime.datetime(2024, 2, 20, 14, 15, 30, 0)
+        tombstone_artifact.parse_protobuf(file_name, file_timestamp, data)
+
+        assert len(tombstone_artifact.results) == 1
+        result = tombstone_artifact.results[0]
+
+        # Verify timestamp fallback
+        assert result.get("timestamp") == "2024-02-20 14:15:30.000000"
+        assert result.get("pid") == 9876
+        assert result.get("uid") == 10001
+        assert result.get("signal_info", {}).get("name") == "SIGABRT"
+        assert result.get("process_name") == "ExampleThread"
+
+    def test_tombstone_pb_whitespace_timestamp(self):
+        """Test parsing a protobuf tombstone with whitespace-only timestamp."""
+        tombstone_artifact = TombstoneCrashArtifact()
+        artifact_path = (
+            "android_data/bugreport_tombstones/tombstone_whitespace_timestamp.pb"
+        )
+        file = get_artifact(artifact_path)
+        with open(file, "rb") as f:
+            data = f.read()
+
+        file_name = os.path.basename(artifact_path)
+        file_timestamp = datetime.datetime(2024, 3, 10, 8, 0, 0, 0)
+        tombstone_artifact.parse_protobuf(file_name, file_timestamp, data)
+
+        assert len(tombstone_artifact.results) == 1
+        result = tombstone_artifact.results[0]
+
+        # Verify whitespace timestamp is treated as empty
+        assert result.get("timestamp") == "2024-03-10 08:00:00.000000"
+        assert result.get("pid") == 11111
+        assert result.get("uid") == 2000
+        assert result.get("signal_info", {}).get("name") == "SIGILL"
+
+    def test_tombstone_pb_empty_file(self):
+        """Test that empty (0 bytes) tombstone files are handled gracefully."""
+        tombstone_artifact = TombstoneCrashArtifact()
+        artifact_path = "android_data/bugreport_tombstones/tombstone_empty_file.pb"
+        file = get_artifact(artifact_path)
+        with open(file, "rb") as f:
+            data = f.read()
+
+        # Verify the file is actually empty
+        assert len(data) == 0, "Test file should be empty (0 bytes)"
+
+        file_name = os.path.basename(artifact_path)
+        file_timestamp = datetime.datetime(2024, 4, 1, 12, 0, 0, 0)
+
+        # Empty files should be skipped in the module (not parsed)
+        # So we don't call parse_protobuf here, just verify the data is empty
+        # The actual skipping happens in the Tombstones module's run() method
+        # This test verifies that empty data is detectable
+        assert len(data) == 0