From a649467fd7c8f5b8527ed6d990e969b549b2bde4 Mon Sep 17 00:00:00 2001
From: graham <graham.annett@gmail.com>
Date: Wed, 13 Mar 2024 15:50:27 -0600
Subject: [PATCH 1/2] Union handles lists

---
 simple_parsing/wrappers/field_wrapper.py |  9 +++++++++
 test/test_union.py                       | 23 +++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/simple_parsing/wrappers/field_wrapper.py b/simple_parsing/wrappers/field_wrapper.py
index 3a4d1860..c9d71e21 100644
--- a/simple_parsing/wrappers/field_wrapper.py
+++ b/simple_parsing/wrappers/field_wrapper.py
@@ -330,6 +330,8 @@ def get_arg_options(self) -> dict[str, Any]:
         elif self.is_union:
             logger.debug("Parsing a Union type!")
             _arg_options["type"] = get_parsing_fn(self.type)
+            if any(utils.is_list(o) for o in utils.get_args(self.type)):
+                _arg_options["nargs"] = "*"
 
         elif self.is_enum:
             logger.debug(f"Adding an Enum attribute '{self.name}'")
@@ -501,6 +503,13 @@ def postprocess(self, raw_parsed_value: Any) -> Any:
             else:
                 return raw_parsed_value
 
+        elif self.is_union:
+            list_in = [utils.is_list(o) for o in utils.get_args(self.type)]
+            # if type is like Union[str, list[str]] and only a single value was passed,
+            if any(list_in) and (not all(list_in)) and (len(raw_parsed_value) == 1):
+                raw_parsed_value = raw_parsed_value[0]
+            return raw_parsed_value
+
         elif self.is_subparser:
             return raw_parsed_value
 
diff --git a/test/test_union.py b/test/test_union.py
index 4c0027dd..53bfe476 100644
--- a/test/test_union.py
+++ b/test/test_union.py
@@ -32,3 +32,26 @@ class Foo2(TestSetup):
 
     foo = Foo2.setup("--x 2")
     assert foo.x == 2 and type(foo.x) is int
+
+
+def test_union_type_with_list():
+
+    @dataclass
+    class Foo(TestSetup):
+        x: Union[str, list[str]]
+
+    foo = Foo.setup("--x bob")
+    assert foo.x == "bob"
+
+    foo = Foo.setup("--x bob alice")
+    assert foo.x == ["bob", "alice"]
+
+    @dataclass
+    class Foo(TestSetup):
+        x: Union[list[int], list[str]]
+
+    foo = Foo.setup("--x bob alice")
+    assert foo.x == ["bob", "alice"]
+
+    foo = Foo.setup("--x 1 2")
+    assert foo.x == [1, 2]

From ed523986f777814f2683f8c059a625bbcc7434b2 Mon Sep 17 00:00:00 2001
From: graham <graham.annett@gmail.com>
Date: Tue, 19 Mar 2024 14:13:39 -0600
Subject: [PATCH 2/2] ran precommit

---
 test/test_union.py | 1 -
 1 file changed, 1 deletion(-)

diff --git a/test/test_union.py b/test/test_union.py
index 53bfe476..e90a39ac 100644
--- a/test/test_union.py
+++ b/test/test_union.py
@@ -35,7 +35,6 @@ class Foo2(TestSetup):
 
 
 def test_union_type_with_list():
-
     @dataclass
     class Foo(TestSetup):
         x: Union[str, list[str]]