fix: pr comments

Author: jakelorocco

mellea/core/base.py

@@ -585,9 +585,10 @@ def __init__(self, thunk: ModelOutputThunk[S]) -> None:
         Uses zero-copy class reassignment: calling `ComputedModelOutputThunk(thunk)` reassigns
         the thunk's `__class__` to `ComputedModelOutputThunk` without creating a new object.
         """
-        if not self.is_computed():
+        # Call the underlying value. It's already been cast as a ComputedModelOutputThunk, so it's .is_computed() value is always True.
+        if not self._computed:
             raise ValueError(
-                "ComputedModelOutputThunk requires a computed ModelOutputThunk; but .is_computed() is False."
+                "ComputedModelOutputThunk requires a computed ModelOutputThunk; but ._computed is False."
             )
         if self.value is None:
             raise ValueError("ComputedModelOutputThunk requires a non-None value.")
@@ -600,7 +601,7 @@ async def avalue(self) -> str:
     async def astream(self) -> str:
         """Cannot astream from ComputedModelOutputThunks. Use .value() instead."""
         raise RuntimeError(
-            "Cannot stream from a ComputedModelOutputThunk."
+            "Cannot stream from a ComputedModelOutputThunk. "
             "This thunk is already fully computed and does not support streaming."
         )
 

test/core/test_computed_model_output_thunk.py

@@ -22,8 +22,13 @@ def test_computed_thunk_requires_computed_thunk():
     """Test that ComputedModelOutputThunk requires a computed ModelOutputThunk."""
     uncomputed_thunk = ModelOutputThunk(value=None)
 
+    assert not uncomputed_thunk._computed, (
+        "thunk should be uncomputed when passed a None value"
+    )
+
     with pytest.raises(
-        ValueError, match="ComputedModelOutputThunk requires a non-None value"
+        ValueError,
+        match="ComputedModelOutputThunk requires a computed ModelOutputThunk;",
     ):
         ComputedModelOutputThunk(uncomputed_thunk)