Incorrect fill in graph objects when connectgaps is set to false

[NoniosTheMad]

Whenever a graph object has the following parameters:
First series -> fill='tonexty',
Second series -> connectgaps=False

The fill connects the first point of this series with the first point of the last segment after "gaps" from the second series, instead of its respective first value.

Here is a basic example

import plotly.graph_objects as go

fig = go.Figure()

def remove_from_list(lst, idx):
    return lst[:idx] + [None] + lst[idx+1:]

x = [i for i in range(5)]

y = [1 for _ in x]
fig.add_trace(go.Scatter(
    x=x,
    y=remove_from_list(y, 2),
    connectgaps=False
))

y = [2 for _ in x]
fig.add_trace(go.Scatter(
    x=x,
    y=y,
    fill='tonexty',
))

fig.show()

Here is another example with more than 1 gap in the data:

import plotly.graph_objects as go

fig = go.Figure()

def remove_from_list(lst, idx):
    return lst[:idx] + [None] + lst[idx+1:]

x = [i for i in range(8)]

y = [1 for _ in x]
fig.add_trace(go.Scatter(
    x=x,
    y=remove_from_list(remove_from_list(y, 2), 5),
    connectgaps=False
))

y = [2 for _ in x]
fig.add_trace(go.Scatter(
    x=x,
    y=y,
    fill='tonexty',
))

fig.show()

I've also attached their respective figure outuputs.

Finally, I have an additional comment regarding how areas are filled.
The following shows another basic example with gaps in both series, and both with connectgaps=False.

import plotly.graph_objects as go

fig = go.Figure()

def remove_from_list(lst, idx):
    return lst[:idx] + [None] + lst[idx+1:]

x = [i for i in range(5)]

y = [1 for _ in x]
fig.add_trace(go.Scatter(
    x=x,
    y=remove_from_list(y, 2),
    connectgaps=False
))

y = [2 for _ in x]
fig.add_trace(go.Scatter(
    x=x,
    y=remove_from_list(y, 2),
    fill='tonexty',
    connectgaps=False
))

fig.show()

The connected area spans even the places where the values are undefined (during a gap). My expectation would be the opposite:

[gvwilson]

Thanks for the bug report @NoniosTheMad - can you please run pip list or the equivalent and give us the versions of Python and plotly.py you're using? thanks - @gvwilson

[NoniosTheMad]

Of course:

Package Version

---

asttokens 3.0.0
attrs 25.3.0
colorama 0.4.6
comm 0.2.2
debugpy 1.8.13
decorator 5.2.1
executing 2.2.0
fastjsonschema 2.21.1
ipykernel 6.29.5
ipython 9.0.2
ipython_pygments_lexers 1.1.1
jedi 0.19.2
jsonschema 4.23.0
jsonschema-specifications 2024.10.1
jupyter_client 8.6.3
jupyter_core 5.7.2
matplotlib-inline 0.1.7
narwhals 1.31.0
nbformat 5.10.4
nest-asyncio 1.6.0
packaging 24.2
parso 0.8.4
pip 24.3.1
platformdirs 4.3.7
plotly 6.0.1
prompt_toolkit 3.0.50
psutil 7.0.0
pure_eval 0.2.3
Pygments 2.19.1
python-dateutil 2.9.0.post0
pywin32 310
pyzmq 26.3.0
referencing 0.36.2
rpds-py 0.23.1
six 1.17.0
stack-data 0.6.3
tornado 6.4.2
traitlets 5.14.3
typing_extensions 4.12.2
wcwidth 0.2.13