fix: support nested generics with partial (#1207)

Co-authored-by: Jason Liu <[email protected]>

instructor/dsl/partial.py

@@ -10,6 +10,9 @@
 
 from jiter import from_json
 from pydantic import BaseModel, create_model
+from typing import Union
+import types
+import sys
 from pydantic.fields import FieldInfo
 from typing import (
     Any,
@@ -29,6 +32,12 @@
 
 T_Model = TypeVar("T_Model", bound=BaseModel)
 
+if sys.version_info >= (3, 10):
+    # types.UnionType is only available in Python 3.10 and above
+    UNION_ORIGINS = (Union, types.UnionType)
+else:
+    UNION_ORIGINS = (Union,)
+
 
 class MakeFieldsOptional:
     pass
@@ -38,6 +47,37 @@ class PartialLiteralMixin:
     pass
 
 
+def _process_generic_arg(
+    arg: Any,
+    make_fields_optional: bool = False,
+) -> Any:
+    arg_origin = get_origin(arg)
+    if arg_origin is not None:
+        # Handle any nested generic type (Union, List, Dict, etc.)
+        nested_args = get_args(arg)
+        modified_nested_args = tuple(
+            _process_generic_arg(
+                t,
+                make_fields_optional=make_fields_optional,
+            )
+            for t in nested_args
+        )
+        # Special handling for Union types (types.UnionType isn't subscriptable)
+        if arg_origin in UNION_ORIGINS:
+            return Union[modified_nested_args]  # type: ignore
+
+        return arg_origin[modified_nested_args]
+    else:
+        if isinstance(arg, type) and issubclass(arg, BaseModel):
+            return (
+                Partial[arg, MakeFieldsOptional]  # type: ignore[valid-type]
+                if make_fields_optional
+                else Partial[arg]
+            )
+        else:
+            return arg
+
+
 def _make_field_optional(
     field: FieldInfo,
 ) -> tuple[Any, FieldInfo]:
@@ -51,14 +91,8 @@ def _make_field_optional(
         generic_base = get_origin(annotation)
         generic_args = get_args(annotation)
 
-        # Recursively apply Partial to each of the generic arguments
         modified_args = tuple(
-            (
-                Partial[arg, MakeFieldsOptional]  # type: ignore[valid-type]
-                if isinstance(arg, type) and issubclass(arg, BaseModel)
-                else arg
-            )
-            for arg in generic_args
+            _process_generic_arg(arg, make_fields_optional=True) for arg in generic_args
         )
 
         # Reconstruct the generic type with modified arguments
@@ -72,10 +106,10 @@ def _make_field_optional(
         tmp_field.annotation = Optional[Partial[annotation, MakeFieldsOptional]]  # type: ignore[assignment, valid-type]
         tmp_field.default = {}
     else:
-        tmp_field.annotation = Optional[field.annotation]  # type: ignore[assignment]
+        tmp_field.annotation = Optional[field.annotation]
         tmp_field.default = None
 
-    return tmp_field.annotation, tmp_field  # type: ignore
+    return tmp_field.annotation, tmp_field
 
 
 class PartialBase(Generic[T_Model]):
@@ -360,15 +394,7 @@ def _wrap_models(field: FieldInfo) -> tuple[object, FieldInfo]:
                 generic_base = get_origin(annotation)
                 generic_args = get_args(annotation)
 
-                # Recursively apply Partial to each of the generic arguments
-                modified_args = tuple(
-                    (
-                        Partial[arg]
-                        if isinstance(arg, type) and issubclass(arg, BaseModel)
-                        else arg
-                    )
-                    for arg in generic_args
-                )
+                modified_args = tuple(_process_generic_arg(arg) for arg in generic_args)
 
                 # Reconstruct the generic type with modified arguments
                 tmp_field.annotation = (

tests/dsl/test_partial.py

@@ -1,5 +1,6 @@
 # type: ignore[all]
 from pydantic import BaseModel, Field
+from typing import Optional, Union
 from instructor.dsl.partial import Partial, PartialLiteralMixin
 import pytest
 import instructor
@@ -20,6 +21,24 @@ class SamplePartial(BaseModel):
     b: SampleNestedPartial
 
 
+class NestedA(BaseModel):
+    a: str
+    b: Optional[str]
+
+
+class NestedB(BaseModel):
+    c: str
+    d: str
+    e: list[Union[str, int]]
+    f: str
+
+
+class UnionWithNested(BaseModel):
+    a: list[Union[NestedA, NestedB]]
+    b: list[NestedA]
+    c: NestedB
+
+
 def test_partial():
     partial = Partial[SamplePartial]
     assert partial.model_json_schema() == {
@@ -166,3 +185,10 @@ class Summary(BaseModel, PartialLiteralMixin):
         previous_summary = extraction.summary
 
     assert updates == 1
+
+
+def test_union_with_nested():
+    partial = Partial[UnionWithNested]
+    partial.get_partial_model().model_validate_json(
+        '{"a": [{"b": "b"}, {"d": "d"}], "b": [{"b": "b"}], "c": {"d": "d"}, "e": [1, "a"]}'
+    )