fix(tests): update test mocks to use safe_write instead of builtins.open

safe_write uses tempfile.mkstemp + os.fdopen internally, so tests that
mock builtins.open to inject errors (PermissionError, FileNotFoundError,
etc.) were bypassed. Update all save-related tests across three test
files to patch safe_write directly.

Also fix pyright type error by changing write_func signature from
Callable[[IO[str]], None] to Callable[[IO[str]], object] since
f.write() returns int.

Signed-off-by: Yash Goel <yashgoel892@gmail.com>

Author: yashhzd

ardupilot_methodic_configurator/backend_safe_file_io.py

@@ -15,7 +15,7 @@
 from typing import IO, Callable
 
 
-def safe_write(filepath: str, write_func: Callable[[IO[str]], None]) -> None:
+def safe_write(filepath: str, write_func: Callable[[IO[str]], object]) -> None:
     """
     Write to a temporary file, then atomically replace the target.
 

tests/test_backend_filesystem_json_with_schema.py

@@ -432,7 +432,9 @@ def test_user_can_save_valid_data_successfully(self, json_manager_with_schema) -
                 "ardupilot_methodic_configurator.backend_filesystem_json_with_schema.os_path.join",
                 return_value="/output/directory/output.json",
             ),
-            patch("builtins.open", mock_open()) as mock_file,
+            patch(
+                "ardupilot_methodic_configurator.backend_filesystem_json_with_schema.safe_write",
+            ) as mock_safe_write,
             patch(
                 "ardupilot_methodic_configurator.backend_filesystem_json_with_schema.json_dumps",
                 return_value='{"name": "Test Output", "count": 42}',
@@ -444,7 +446,7 @@ def test_user_can_save_valid_data_successfully(self, json_manager_with_schema) -
             # Assert: Data saved successfully
             assert error_occurred is False
             assert error_message == ""
-            mock_file.assert_called_once_with("/output/directory/output.json", "w", encoding="utf-8", newline="\n")
+            mock_safe_write.assert_called_once()
             mock_dumps.assert_called_once_with(valid_data, indent=4)
             # Assert: Internal cache updated immediately (regression test for commit ccc53bb)
             assert json_manager_with_schema.data == valid_data
@@ -501,7 +503,10 @@ def test_user_handles_missing_directory_error(self, json_manager_with_schema) ->
                 "ardupilot_methodic_configurator.backend_filesystem_json_with_schema.os_path.join",
                 return_value="/nonexistent/directory/output.json",
             ),
-            patch("builtins.open", side_effect=FileNotFoundError),
+            patch(
+                "ardupilot_methodic_configurator.backend_filesystem_json_with_schema.safe_write",
+                side_effect=FileNotFoundError,
+            ),
             patch("ardupilot_methodic_configurator.backend_filesystem_json_with_schema.logging_error") as mock_error,
         ):
             # Act: User attempts to save to missing directory
@@ -530,7 +535,10 @@ def test_user_handles_permission_denied_error(self, json_manager_with_schema) ->
                 "ardupilot_methodic_configurator.backend_filesystem_json_with_schema.os_path.join",
                 return_value="/protected/directory/output.json",
             ),
-            patch("builtins.open", side_effect=PermissionError),
+            patch(
+                "ardupilot_methodic_configurator.backend_filesystem_json_with_schema.safe_write",
+                side_effect=PermissionError,
+            ),
             patch("ardupilot_methodic_configurator.backend_filesystem_json_with_schema.logging_error") as mock_error,
         ):
             # Act: User attempts to save without permissions
@@ -559,7 +567,10 @@ def test_user_handles_directory_instead_of_file_error(self, json_manager_with_sc
                 "ardupilot_methodic_configurator.backend_filesystem_json_with_schema.os_path.join",
                 return_value="/test/directory/output.json",
             ),
-            patch("builtins.open", side_effect=IsADirectoryError),
+            patch(
+                "ardupilot_methodic_configurator.backend_filesystem_json_with_schema.safe_write",
+                side_effect=IsADirectoryError,
+            ),
             patch("ardupilot_methodic_configurator.backend_filesystem_json_with_schema.logging_error") as mock_error,
         ):
             # Act: User attempts to save to directory path
@@ -589,7 +600,10 @@ def test_user_handles_os_error_gracefully(self, json_manager_with_schema) -> Non
                 "ardupilot_methodic_configurator.backend_filesystem_json_with_schema.os_path.join",
                 return_value="/test/directory/output.json",
             ),
-            patch("builtins.open", side_effect=os_error),
+            patch(
+                "ardupilot_methodic_configurator.backend_filesystem_json_with_schema.safe_write",
+                side_effect=os_error,
+            ),
             patch("ardupilot_methodic_configurator.backend_filesystem_json_with_schema.logging_error") as mock_error,
         ):
             # Act: User encounters OS error
@@ -619,7 +633,6 @@ def test_user_handles_json_serialization_errors(self, json_manager_with_schema)
                 "ardupilot_methodic_configurator.backend_filesystem_json_with_schema.os_path.join",
                 return_value="/test/directory/output.json",
             ),
-            patch("builtins.open", mock_open()),
             patch(
                 "ardupilot_methodic_configurator.backend_filesystem_json_with_schema.json_dumps",
                 side_effect=TypeError("Object not serializable"),
@@ -652,7 +665,6 @@ def test_user_handles_json_value_errors(self, json_manager_with_schema) -> None:
                 "ardupilot_methodic_configurator.backend_filesystem_json_with_schema.os_path.join",
                 return_value="/test/directory/output.json",
             ),
-            patch("builtins.open", mock_open()),
             patch(
                 "ardupilot_methodic_configurator.backend_filesystem_json_with_schema.json_dumps",
                 side_effect=ValueError("Circular reference in data"),
@@ -687,7 +699,10 @@ def test_user_handles_unexpected_errors_gracefully(self, json_manager_with_schem
                 "ardupilot_methodic_configurator.backend_filesystem_json_with_schema.os_path.join",
                 return_value="/test/directory/output.json",
             ),
-            patch("builtins.open", side_effect=unexpected_error),
+            patch(
+                "ardupilot_methodic_configurator.backend_filesystem_json_with_schema.safe_write",
+                side_effect=unexpected_error,
+            ),
             patch("ardupilot_methodic_configurator.backend_filesystem_json_with_schema.logging_error") as mock_error,
         ):
             # Act: User encounters unexpected error
@@ -731,10 +746,10 @@ def test_user_completes_full_workflow_successfully(self) -> None:
             ),
             patch(
                 "builtins.open",
-                side_effect=[
-                    mock_open(read_data=json.dumps(schema_data)).return_value,  # Schema file
-                    mock_open().return_value,  # Data file for saving
-                ],
+                return_value=mock_open(read_data=json.dumps(schema_data)).return_value,  # Schema file
+            ),
+            patch(
+                "ardupilot_methodic_configurator.backend_filesystem_json_with_schema.safe_write",
             ),
             patch(
                 "ardupilot_methodic_configurator.backend_filesystem_json_with_schema.json_dumps",

tests/test_backend_filesystem_program_settings.py

@@ -578,14 +578,16 @@ def test_user_can_save_settings_to_file(self, mock_user_config) -> None:
         with (
             patch.object(ProgramSettings, "_user_config_dir", return_value=mock_user_config["config_dir"]),
             patch("os.path.join", return_value=mock_user_config["settings_file"]),
-            patch("builtins.open", mock_open()) as mock_file,
+            patch(
+                "ardupilot_methodic_configurator.backend_filesystem_program_settings.safe_write",
+            ) as mock_safe_write,
         ):
             # Act: Save settings to file
             ProgramSettings._set_settings_from_dict(mock_settings)
 
-            # Assert: File is opened correctly and data is written
-            mock_file.assert_called_once_with(mock_user_config["settings_file"], "w", encoding="utf-8", newline="\n")
-            mock_file().write.assert_called()
+            # Assert: safe_write is called with the correct file path
+            mock_safe_write.assert_called_once()
+            assert mock_safe_write.call_args[0][0] == mock_user_config["settings_file"]
 
 
 class TestUsagePopupSettings: