fix: parse list-valued plugin settings with nargs

src/snakemake_interface_common/plugin_registry/plugin.py

@@ -335,6 +335,10 @@ def _get_prefixed_name(self, field_name: str) -> str:
     def _parse_type(self, thefield: Field, value: Any, thetype: Any) -> Any:
         def apply_type(value: Any, thetype: Any) -> Any:
             try:
+                if typing.get_origin(thetype) is list:
+                    thetype = typing.get_args(thetype)[0]
+                if isinstance(value, list) and thetype is not list:
+                    return [thetype(item) for item in value]
                 return thetype(value)
             except Exception as e:
                 raise WorkflowError(

tests/tests.py

@@ -1,5 +1,5 @@
-from dataclasses import dataclass
-from typing import Optional
+from dataclasses import dataclass, field
+from typing import List, Optional
 import pytest
 
 from snakemake_interface_common import at_least_snakemake_version
@@ -140,6 +140,35 @@ def __init__(self):
     assert settings.optional_int is None
 
 
+@dataclass
+class ListSettings(SettingsBase):
+    mounts: Optional[List[str]] = field(
+        default=None, metadata={"help": "mounts", "nargs": "+"}
+    )
+    ints: List[int] = field(
+        default_factory=list, metadata={"help": "ints", "nargs": "+"}
+    )
+
+
+class ListPlugin(TestPlugin):
+    @property
+    def settings_cls(self):
+        return ListSettings
+
+
+@pytest.mark.parametrize(
+    "mounts, ints", [(["/a:/a", "/b:/b"], [1, 2]), (["/a:/a"], ["1", "2"])]
+)
+def test_settings_list_nargs(mounts, ints):
+    class MockArgs:
+        test_mounts = mounts
+        test_ints = ints
+
+    settings = ListPlugin().get_settings(MockArgs())
+    assert settings.mounts == mounts
+    assert settings.ints == [1, 2]
+
+
 def test_access_pattern_str():
     from snakemake_interface_common.io import AccessPattern