conditional warning for excluding special files

borgmatic/borg/create.py

@@ -430,18 +430,17 @@ def create_archive(
             borg_environment,
             skip_directories=borgmatic_source_directories,
         )
-        logger.warning(
-            f'{repository}: Excluding special files to prevent Borg from hanging: {", ".join(special_file_paths)}'
-        )
-
-        exclude_file = write_pattern_file(
-            expand_home_directories(
-                tuple(location_config.get('exclude_patterns') or ()) + special_file_paths
-            ),
-            pattern_file=exclude_file,
-        )
 
-        if exclude_file:
+        if special_file_paths:
+            logger.warning(
+                f'{repository}: Excluding special files to prevent Borg from hanging: {", ".join(special_file_paths)}'
+            )
+            exclude_file = write_pattern_file(
+                expand_home_directories(
+                    tuple(location_config.get('exclude_patterns') or ()) + special_file_paths
+                ),
+                pattern_file=exclude_file,
+            )
             create_command += make_exclude_flags(location_config, exclude_file.name)
 
     create_command += (

tests/unit/borg/test_create.py

@@ -1790,7 +1790,7 @@ def test_create_archive_with_stream_processes_ignores_read_special_false_and_log
     flexmock(module).should_receive('pattern_root_directories').and_return([])
     flexmock(module.os.path).should_receive('expanduser').and_raise(TypeError)
     flexmock(module).should_receive('expand_home_directories').and_return(())
-    flexmock(module).should_receive('write_pattern_file').and_return(None)
+    flexmock(module).should_receive('write_pattern_file').and_return(flexmock(name='/tmp/excludes'))
     flexmock(module.feature).should_receive('available').and_return(True)
     flexmock(module).should_receive('ensure_files_readable')
     flexmock(module.logger).should_receive('warning').twice()
@@ -1800,7 +1800,7 @@ def test_create_archive_with_stream_processes_ignores_read_special_false_and_log
         (f'repo::{DEFAULT_ARCHIVE_NAME}',)
     )
     flexmock(module.environment).should_receive('make_environment')
-    flexmock(module).should_receive('collect_special_file_paths').and_return(())
+    flexmock(module).should_receive('collect_special_file_paths').and_return(("/dev/null",))
     create_command = (
         'borg',
         'create',