go.Figure clobbers user uids

[alexcjohnson]

default usage of go.Figure does not allow users to enter uid for traces. That seems to be because it calls self._data_validator = DataValidator(set_uid=True) that triggers:

plotly.py/_plotly_utils/basevalidators.py

Lines 2359 to 2361 in bb5c998

	if self.set_uid:
	for trace in v:
	trace.uid = str(uuid.uuid4())

Can we override uid only if it wasn't set by the user?

Discovered while debugging https://community.plot.ly/t/preserving-ui-state-like-zoom-in-dcc-graph/15793/34

[alexcjohnson]

In fact for uirevision purposes it would be better if uid were never set (then as far as uirevision is concerned, the trace order becomes the uid). What was the purpose to include this in the first place?

[jonmmease]

Thanks for tracking that down @alexcjohnson. The reason that the trace uid was being set on the Python side was to support the needs of FigureWidget. In this case the front end sends the default properties back to the Python side after every figure update and so plotly.py uses the uid to associate these updates with the proper trace. Trace index isn't enough because the updates are sent from JavaScript to Python asynchronously and so trace reordering could have occurred in the meantime.

But, I think we should be able to work out a way to only set the UID when traces are added to a FigureWidget instance. FigureWidget doesn't user react, so the uirevision considerations shouldn't be a factor there.

[alexcjohnson]

Ah, yes - would be great if only FigureWidget added uid, not Figure. That way Dash users wouldn't have to think about uid at all unless they want to preserve trace user interactions across reordered traces.

Even for FigureWidget I wonder if you could honor user-provided uid and only fill in missing ones, but there may not be an actual use case for that.

[jonmmease]

Alright if we take care of this for v4 (a couple of months out)? I think there is a small chance that this could be a breaking change for some applications built on top of plotly.py.

Even for FigureWidget I wonder if you could honor user-provided uid and only fill in missing ones, but there may not be an actual use case for that.

I think I was concerned that things would fail badly if a user ended up adding multiple traces with the same not-unique uid.