[Bug] connectNulls option is ignored by stacked areas

[EmmadUsmani]

Version

5.4.3

Link to Minimal Reproduction

https://echarts.apache.org/examples/en/editor.html?c=line-simple&code=PYBwLglsB2AEC8sDeAoWsAmBDMWDOApmAFzJrqYQC2B0eUdpA2gEQAeLANLCwJ5c9eAJhYBdTuXR5gAVwBOAYwLNJFJLDakAjN17bdQ0gFZYAXwkU1G0kN2loMgDaODpACxmLl5NdgBmO39XWC1PVVFyc3I2AEE2CDxSVEswXhBlWAByBRwCAHNgOV5Mryj0XjiEpNVU9NJMgDcsRxkCTMivQjkIAkTYJlVk71qMzMcIaDavSwUYSYUwADknRz6wOVbpiiw5AiwAZVTHDKQy71pZjBPVS00eDi3LPUEuG7DvWDxcBQBrUhYvlhfq9LGd0EMUmlRuNJiU3rNoPMlis1hsCI9YDs9odeMckmCKBdgFdqh90Hd2CCyc8-CIMQSpN8_jxAcCtqZyBFTABuIA

Steps to Reproduce

Is visible in the reproduction

Current Behavior

The green area of the second series (y2) dips below the first series (y) at x=2, where y is null

Expected Behavior

The green area of the second series (y2) should not dip below the first series (y) at x=2, where y is null. Instead, because the connectNulls option is true, it should behave as if an interpolated value of y=2 is there, and render its line and area accordingly.

Environment

- OS: macOS 13.6.2
- Browser: Firefox 123.0b7

Any additional comments?

Seems like this issue was reported twice before, but those threads are old and inactive
#12404
#17135

[EmmadUsmani]

I would be willing to attempt a fix for this if it's not too difficult, just want to confirm first that the expected behavior seems correct to the maintainers.

[EmmadUsmani]

My colleague @alxnddr has a fix in progress: #19602

It fixes the first test case in area-stack.html

Before	After

[helgasoft]

Here we go again with the fundamental question - How far should a chart library go to accommodate data exceptions?
Line chart has connectNulls, yes but it displays only existing points and line series are independent.
Stacked line chart now correctly shows the missing data. But you say "it should behave as if an interpolated value of y=2 is there".
Doesn't that mean that ECharts should fabricate data ?
I think such responsibility should be taken by the developer, not by the chart library.