Buggy lines with Dates & gaps

[jacobsorme]

Expected Behavior

I expect the data to be stacked on the Date of the data. Two data points at the same Date is expected to be stacked.

Current Behavior

The x-position of the data in the graph seem to be correctly positioned among the Dates. However, the y-position seem to still rely on the index - it does not change as the starting Date of the dataset changes (see images 2, 3 and 4). Note that the blue line always start at y-position 5.

Not only is the y-position buggy, but the area under the graphs look strange, and seem to work with the indices rather than the Dates. See image

Figure 1) Normal behavior, datasets start at same time.

Figure 2) Strange behavior, one dataset (blue) start at a time-offset.

Figure 3) Strange behavior, one dataset (blue) start at a large time-offset.

Figure 4) Strange behavior, one dataset (blue) start at a large time-offset. Now with fill-parameter of dataset set to origin instead of filling mode relative to dataset index.

Figure 5) No stacking. Chart for reference.

Possible Solution

This issue is similar to #6437 - indices and Dates seem to get mixed up. Parts of the graph seem to still rely on an index (like the stacking/area/height of line here) while other parts (the x-position here) relies on the Date.

I am more than willing to try and help with fix this, maybe with some help on what files to start looking at.

Steps to Reproduce

See JSbin

Context

I am trying to stack things that not necessarily start/exist on the same dates, data categories that come and go as
time passes.

Environment

• Chart.js version: 2.9.3
• Browser name and version: Safari
• Link to your project:

[kurkle]

This has been fixed in 3.0.0-alpha