FunctionalProperty `constraints` are in the public api but are not validated.

[julianstirling]

Since finding out I can do:

    @lt.setting
    def microscope_id(self) -> UUID:
        """A unique identifier for this microscope."""
        if self._microscope_id is None:
            self._microscope_id = str(uuid4())
        return UUID(self._microscope_id)

    @microscope_id.setter
    def _set_microscope_id(self, uuid: UUID) -> None:
        self._microscope_id = str(uuid)

    microscope_id.readonly = True

I am realising I can set the other attributes of the descriptor including constraints such as:

    @lt.setting
    def microscope_id(self) -> UUID:
        """A unique identifier for this microscope."""
        if self._microscope_id is None:
            self._microscope_id = str(uuid4())
        return UUID(self._microscope_id)

    @microscope_id.setter
    def _set_microscope_id(self, uuid: UUID) -> None:
        self._microscope_id = str(uuid)

    microscope_id.constraints = {"min_length": 1}

This propagates through to the thing_descriptions. I think if BaseProperty made constraints a @builtins.propertythen it could either validate it with the setter. Or create aset_constraints` so that this is possible:

    @lt.setting
    def microscope_id(self) -> UUID:
        """A unique identifier for this microscope."""
        if self._microscope_id is None:
            self._microscope_id = str(uuid4())
        return UUID(self._microscope_id)

    @microscope_id.setter
    def _set_microscope_id(self, uuid: UUID) -> None:
        self._microscope_id = str(uuid)

    microscope_id.set_constraints(min_length=1)

which feels like nicer syntax.

[rwb27]

Just to be clear, when you say constraints aren't validated, you mean there's no check that the constraint keys are valid? I'm hoping that (valid) constraints do get applied when the property is set over HTTP?

Adding a check would be good - and easy, if we use a property. I'll make a PR.

[julianstirling]

I mean the bit in the red box isn't run, so the bit that gives you a helpful validation error.

[rwb27]

thanks, yes. This is fixed in #277, and then I got carried away and validated it properly with pydantic. I see I even made a note somewhere that it wasn't validated when it was set directly - it's now validated, and tested.

I think this is exactly the sort of thing that TypedDict is good for - but if it turns out to be really annoying I'm not against doing something else.