Merge pull request #151 from DanCardin/dc/parser-dont-store-has-value…

…-false

fix: Avoid storing has_value=False values in the parser.

docs/source/arg.md

@@ -406,4 +406,7 @@ Principally, `Annotated[SubObject | None, Arg.destructured()]` **could** make se
 child options are therefore optional, or that if any child attributes are missing, then that implies
 `sub_object=None` at the top level. However both of these are mechanically much more complex than the
 feature, as it exists today.
+
+Additionally, this feature only works with the native backend. This **probably** has a workable
+solution for argparse, so file an issue if this affects you!
 ```

src/cappa/parser.py

@@ -590,7 +590,9 @@ def consume_arg(
         fulfilled_deps[RawOption] = option
 
     kwargs = fulfill_deps(action_handler, fulfilled_deps)
-    context.result[field_name] = action_handler(**kwargs)
+    result = action_handler(**kwargs)
+    if arg.has_value:
+        context.result[field_name] = result
 
     check_deprecated(context, arg, option)
 

tests/arg/test_destructured.py

@@ -64,3 +64,27 @@ def test_destructured_optional():
         str(e.value)
         == "Destructured arguments currently only support singular concrete types."
     )
+
+
+@dataclass
+class CollisionSub:
+    field1: str = ""
+    field2: Annotated[str, cappa.Arg(long=True)] = ""
+
+
+@dataclass
+class Collision:
+    sub: Annotated[CollisionSub, cappa.Arg.destructure()]
+    field1: int = 0
+    field2: int = 0
+
+
+def test_destructured_collision():
+    result = parse(Collision, "1")
+    assert result == Collision(sub=CollisionSub("1", ""), field1=0)
+
+    result = parse(Collision, "1", "2")
+    assert result == Collision(sub=CollisionSub("1", ""), field1=2)
+
+    result = parse(Collision, "--field2=-1", "1", "2", "3")
+    assert result == Collision(sub=CollisionSub("1", "-1"), field1=2, field2=3)