fix: Vertex AI: handle "default" in Field

fixes jxnl#837

instructor/client_vertexai.py

@@ -12,10 +12,18 @@
 def _create_gemini_json_schema(model: BaseModel):
     schema = model.model_json_schema()
     schema_without_refs: dict[str, Any] = jsonref.replace_refs(schema)  # type: ignore
+    try:
+        required_params = schema_without_refs["required"]
+    except KeyError:
+        # `schema_without_refs` has no key "required" because all parameters have "default" value set
+        required_params = []
+    # find parameters that have "default" value set, and add them to `required_params`
+    params_with_default = [param for param, description in schema_without_refs["properties"].items() if "default" in description]
+    required_params += params_with_default
     gemini_schema: dict[Any, Any] = {
         "type": schema_without_refs["type"],
         "properties": schema_without_refs["properties"],
-        "required": schema_without_refs["required"],
+        "required": required_params,
     }
     return gemini_schema
 

tests/llm/test_vertexai/test_modes.py

@@ -14,7 +14,7 @@ class Item(BaseModel):
 
 class Order(BaseModel):
     items: list[Item] = Field(..., default_factory=list)
-    customer: str
+    customer: str = Field(default="")
 
 
 @pytest.mark.parametrize("model, mode", product(models, modes))
@@ -49,13 +49,13 @@ def test_nested(model, mode):
 class Book(BaseModel):
     title: str
     author: str
-    genre: str
+    genre: str = Field(default="")
     isbn: str
 
 
 class LibraryRecord(BaseModel):
     books: list[Book] = Field(..., default_factory=list)
-    visitor: str
+    visitor: str = Field(default="")
     library_id: str