How To Handle Path Parameters of Multiple Valid Types

[rgajason]

We have endpoints where a path parameter can be multiple types (string, integer, boolean). These are normally used for filtering. For example:

class Widget(Document):
    name: str
    some_bool: bool
    some_str: str
    some_int: int


class WidgetByAttr(str, Enum):
    # Set of widget attributes that we allow filtering on
    some_bool = "some_bool"
    some_str = "some_str"
    some_int = "some_int"


@get(
    path="/widgets/by-attr/{widget_attr:str}/{attr_value:str}",
    response_description="List Widgets by an attribute value",
)
async def read_widgets_by_attr(
    widget_attr: WidgetByAttr,
    attr_value: Union[int, bool, str],
) -> List[Widget]:
    widgets = []
    for widget in await Widget.find(
        getattr(Widget, widget_attr) == attr_value
    ).to_list(length=100):
        widgets.append(widget)

    return widgets

The data type specified for attr_value in the path seems to be overriding the function signature (Union[...]). In other words, attr_value is always coerced to a string (never int or bool).

Thoughts?

[Goldziher]

You use a union type. Try a different type.

[rgajason]

I tried a couple variations but wasn't able to land on the coercion that I needed to fit my needs. I think part of it is because of the lack of boolean support for path parameters, but the other part is not being able to coerce between integers/int-like items and strings (I think the docs state this, but maybe I'm just changing my interpretation of the docs after testing). For example, none of the permutations I tried allowed me to accept a path parameter that would be an integer if I passed "3" and still allow for a string if I passed "foo".

I worked around this by setting the path param data type to string and then letting Pydantic coerce from within the function:

class Widget(Document):
    name: str
    some_bool: bool
    some_str: str
    some_int: int


class WidgetByAttr(str, Enum):
    # Set of widget attributes that we allow filtering on
    some_bool = "some_bool"
    some_str = "some_str"
    some_int = "some_int"


class WidgetByAttrValue(BaseModel):
    coerced: int | bool | str

    def __init__(self, coerced: int | bool | str, **kwargs) -> None:
        # Workaround for: https://github.com/starlite-api/starlite/discussions/883
        coerced = coerced.lstrip("/")
        super(WidgetByAttrValue, self).__init__(coerced=coerced, **kwargs)


@get(
    path="/widgets/by-attr/{widget_attr:str}/{attr_value:str}",
    response_description="List Widgets by an attribute value",
)
async def read_widgets_by_attr(
    widget_attr: WidgetByAttr,
    attr_value: str,
) -> List[Widget]:
    coerced = WidgetByAttrValue(attr_value).coerced

    widgets = []
    for widget in await Widget.find(
        getattr(Widget, widget_attr) == coerced
    ).to_list(length=100):
        widgets.append(widget)

    return widgets