Revert "fix(vertex): drop bare {} schemas from anyOf before adding nullable=True (#23060)"

This reverts commit 3ad9a536d3.

litellm/llms/vertex_ai/common_utils.py

@@ -712,20 +712,6 @@ def convert_anyof_null_to_nullable(schema, depth=0):
             )
 
         if contains_null:
-            # Drop any-type schemas (bare {}) from anyOf before adding nullable=True.
-            # Adding nullable=True to {} produces {"nullable": True} with no type field,
-            # which Gemini rejects as an anyOf entry without a concrete type.
-            for atype in list(anyof):
-                if isinstance(atype, dict) and _is_any_type_schema(atype):
-                    anyof.remove(atype)
-
-            if len(anyof) == 0:
-                # All remaining entries were any-type schemas (e.g. anyOf: [{}, null]).
-                # This means "any nullable value" — collapse anyOf and mark parent nullable.
-                del schema["anyOf"]
-                schema["nullable"] = True
-                return
-
             # set all types to nullable following guidance found here: https://cloud.google.com/vertex-ai/generative-ai/docs/samples/generativeaionvertexai-gemini-controlled-generation-response-schema-3#generativeaionvertexai_gemini_controlled_generation_response_schema_3-python
             for atype in anyof:
                 # Remove items field if type is array and items is empty

tests/test_litellm/llms/vertex_ai/test_vertex_ai_common_utils.py

@@ -1451,15 +1451,11 @@ def test_add_object_type_preserves_any_type_schema():
     assert schema["type"] == "object"
 
 
-def test_convert_anyof_pure_any_type_collapses_to_nullable_parent():
-    """
-    anyOf: [{}, null] means "any nullable value".
-    The empty schema {} (any-type) inside anyOf cannot receive nullable=True and be
-    sent to Gemini — Gemini rejects {"nullable": True} with no type field as an anyOf
-    entry. Instead we collapse the anyOf and set nullable=True on the parent.
-    """
+def test_convert_anyof_preserves_any_type_members():
+    """Test convert_anyof_null_to_nullable does NOT coerce empty anyOf members to object."""
     from litellm.llms.vertex_ai.common_utils import convert_anyof_null_to_nullable
 
+    # anyOf with empty schema and null — empty should be preserved
     schema = {
         "anyOf": [
             {},
@@ -1467,42 +1463,10 @@ def test_convert_anyof_pure_any_type_collapses_to_nullable_parent():
         ]
     }
     convert_anyof_null_to_nullable(schema)
-    # anyOf should be removed; parent gets nullable=True to represent "any nullable value"
-    assert "anyOf" not in schema
-    assert schema.get("nullable") is True
-
-
-def test_convert_anyof_drops_empty_schema_when_concrete_type_present():
-    """
-    Regression test for tool schemas with anyOf: [array, {}, null].
-    The bare {} (any-type) inside anyOf must be dropped — Gemini rejects
-    {"nullable": True} with no type field. The concrete array type should
-    remain with nullable=True.
-
-    Broken by da941e4261c5 (preserve type schema semantics for JsonValue fields).
-    """
-    from litellm.llms.vertex_ai.common_utils import convert_anyof_null_to_nullable
-
-    schema = {
-        "properties": {
-            "callbacks": {
-                "anyOf": [
-                    {"items": {}, "type": "array"},
-                    {},
-                    {"type": "null"},
-                ]
-            }
-        }
-    }
-    convert_anyof_null_to_nullable(schema)
-
-    callbacks_anyof = schema["properties"]["callbacks"]["anyOf"]
-    # {} and {"type": "null"} should both be gone; only the array entry remains
-    assert len(callbacks_anyof) == 1
-    assert callbacks_anyof[0].get("type") == "array"
-    assert callbacks_anyof[0].get("nullable") is True
-    # empty items should have been stripped too
-    assert "items" not in callbacks_anyof[0]
+    # null should be removed, empty schema should be preserved (not coerced to object)
+    assert len(schema["anyOf"]) == 1
+    assert "type" not in schema["anyOf"][0] or schema["anyOf"][0].get("type") != "object"
+    assert schema["anyOf"][0].get("nullable") is True
 
 
 def test_build_vertex_schema_jsonvalue():