Fix an error when dumping a MySQL database and the "exclude_nodump" option is set (#720).

NEWS

@@ -4,6 +4,7 @@
    variables available for explicit use in your commands. See the documentation for more
    information: https://torsion.org/borgmatic/docs/how-to/run-arbitrary-borg-commands/
  * #719: Fix an error when running "borg key export" through borgmatic.
+ * #720: Fix an error when dumping a MySQL database and the "exclude_nodump" option is set.
  * When merging two configuration files, error gracefully if the two files do not adhere to the same
    format.
 

borgmatic/borg/create.py

@@ -280,14 +280,17 @@ def collect_special_file_paths(
     create_command, local_path, working_directory, borg_environment, skip_directories
 ):
     '''
-    Given a Borg create command as a tuple, a local Borg path, a working directory, and a dict of
+    Given a Borg create command as a tuple, a local Borg path, a working directory, a dict of
     environment variables to pass to Borg, and a sequence of parent directories to skip, collect the
     paths for any special files (character devices, block devices, and named pipes / FIFOs) that
     Borg would encounter during a create. These are all paths that could cause Borg to hang if its
     --read-special flag is used.
     '''
+    # Omit "--exclude-nodump" from the Borg dry run command, because that flag causes Borg to open
+    # files including any named pipe we've created.
     paths_output = execute_command_and_capture_output(
-        create_command + ('--dry-run', '--list'),
+        tuple(argument for argument in create_command if argument != '--exclude-nodump')
+        + ('--dry-run', '--list'),
         capture_stderr=True,
         working_directory=working_directory,
         extra_environment=borg_environment,

tests/unit/borg/test_create.py

@@ -449,6 +449,25 @@ def test_collect_special_file_paths_excludes_non_special_files():
     ) == ('/foo', '/baz')
 
 
+def test_collect_special_file_paths_omits_exclude_no_dump_flag_from_command():
+    flexmock(module).should_receive('execute_command_and_capture_output').with_args(
+        ('borg', 'create', '--dry-run', '--list'),
+        capture_stderr=True,
+        working_directory=None,
+        extra_environment=None,
+    ).and_return('Processing files ...\n- /foo\n+ /bar\n- /baz').once()
+    flexmock(module).should_receive('special_file').and_return(True)
+    flexmock(module).should_receive('any_parent_directories').and_return(False)
+
+    module.collect_special_file_paths(
+        ('borg', 'create', '--exclude-nodump'),
+        local_path=None,
+        working_directory=None,
+        borg_environment=None,
+        skip_directories=flexmock(),
+    )
+
+
 DEFAULT_ARCHIVE_NAME = '{hostname}-{now:%Y-%m-%dT%H:%M:%S.%f}'  # noqa: FS003
 REPO_ARCHIVE_WITH_PATHS = (f'repo::{DEFAULT_ARCHIVE_NAME}', 'foo', 'bar')