Sankey node x and y positions could not be equal to 0 or np.nan

[banderlog]

1. We need to define both x and y or nothing will work allow provision of X coordinates only for Sankey charts #1732
2. We cannot maintain the original position of a node (in R one could just add NA to that vector position)
3. x and/or y should not be equal exactly to 0

Consider example below

# example from <https://plotly.com/python/sankey-diagram/>
import plotly.graph_objects as go

fig = go.Figure(data=[go.Sankey(
    arrangement = "perpendicular",
    node = dict(
      pad = 15,
      thickness = 20,
      line = dict(color = "black", width = 0.5),
      label = ["A1", "A2", "B1", "B2", "C1", "C2"],
      color = "blue",
    ),
    link = dict(
      source = [0, 1, 0, 2, 3, 3], # indices correspond to labels, eg A1, A2, A1, B1, ...
      target = [2, 3, 3, 4, 4, 5],
      value = [8, 4, 2, 8, 4, 2]
  ))])

fig.update_layout(title_text="Basic Sankey Diagram", font_size=10)
fig.show()

Now we want to put A2, B2, C2 before A1,B1,C1 on Y axis:

fig.data[0].node.x = [0., 0., 0.5, 0.5, 1, 1]
fig.data[0].node.y = [1, 0.5, 1, 0.5, 1, 0.5]
fig.show()

We are able to see that A1 and A2 did not change their places. That because they have 0 in x coordinates.
It is easy to fix:

fig.data[0].node.x = [1e-09, 1e-09, 0.5, 0.5, 1, 1]

We are not reloading Ys, just fixing Xs is enough.
Probably plotly.js problem on visualization, but plotly.python problem for letting this.

If we will do something like fig.data[0].node.x = [np.nan, 1e-09, 0.5, 0.5, 1, 1], A1 will behave in the same way as if it would be a 0.

[gvwilson]

Hi - we are trying to tidy up the stale issues and PRs in Plotly's public repositories so that we can focus on things that are still important to our community. Since this one has been sitting for several years, I'm going to close it; if it is still a concern, please add a comment letting us know what recent version of our software you've checked it with so that I can reopen it and add it to our backlog. Thanks for your help - @gvwilson

[egberts]

Reopen it.

[banderlog]

Still there, no surprise, because nothing changed in aforementioned index problem

[avm19]

if it is still a concern, please add a comment letting us know what recent version of our software you've checked it with so that I can reopen it and add it to our backlog. Thanks

@gvwilson Still an issue in version '5.22.0'.

This is a duplicate of #2902, although this issue's author provided a nice analysis and summary.