Fix: Handle optional values properly in input and output component

examples/render_output.py

@@ -1,4 +1,5 @@
 import datetime
+from typing import Optional
 
 from pydantic import BaseModel, Field
 
@@ -9,7 +10,10 @@ class ExampleModel(BaseModel):
     text: str = Field(..., description="A text property")
     integer: int = Field(..., description="An integer property.")
     date: datetime.date = Field(..., description="A date.")
+    optional_datetime: Optional[datetime.datetime] = Field(...,
+        description="An optional datetime property."
+    )
 
 
-instance = ExampleModel(text="Some text", integer=40, date=datetime.date.today())
+instance = ExampleModel(text="Some text", integer=40, date=datetime.date.today(), optional_datetime=datetime.datetime.now())
 sp.pydantic_output(instance)

src/streamlit_pydantic/schema_utils.py

@@ -9,6 +9,25 @@
 def resolve_reference(reference: str, references: Dict) -> Dict:
     return references[reference.split("/")[-1]]
 
+def filter_nullable(property: Dict) -> Dict:
+    # if it is optional and nullable, it may be
+    # - {'anyOf': [{'type': '<type>'}, {'type': 'null'}]
+    # - {'anyOf': [{'$ref': '<ref>'}, {'type': 'null'}]
+    # we want to remove the "null" type
+    union_prop = property.get("oneOf", property.get("anyOf"))
+    if union_prop is not None:
+        # Remove the null type, while keeping the `$ref` and other types
+        where = [i for i,d in enumerate(union_prop) if d.get('type') == "null"]
+        where.reverse()
+        for i in where:
+            del union_prop[i]
+        if len(union_prop) == 1: # it is fine, we wrap the type to the original object
+            for key in union_prop[0]:
+                property[key] = union_prop[0][key]
+
+            del property["anyOf"] # now we can delete the key
+
+    return property
 
 def get_single_reference_item(property: Dict, references: Dict) -> Dict:
     # Ref can either be directly in the properties or the first element of allOf

src/streamlit_pydantic/ui_renderer.py

@@ -1065,6 +1065,8 @@ def _render_list_input(self, streamlit_app: Any, key: str, property: Dict) -> An
         return object_list
 
     def _render_property(self, streamlit_app: Any, key: str, property: Dict) -> Any:
+        # filter the case of optional and nullable
+        property = schema_utils.filter_nullable(property)
         if schema_utils.is_single_enum_property(property, self._schema_references):
             return self._render_single_enum_input(streamlit_app, key, property)
 
@@ -1241,6 +1243,7 @@ def _render_single_output(self, streamlit: Any, output_data: BaseModel) -> None:
                     continue
 
                 if property_schema:
+                    property_schema = schema_utils.filter_nullable(property_schema)
                     if schema_utils.is_multi_file_property(property_schema):
                         for file in output_property_value:
                             self._render_single_file_property(