Hey!
I discovered a bug while developing a custom visual. The problem is that metadata is not passed in my case. Trying on the Power BI Service, but I think the desktop version has the same problem. Here it is:
1. I have a field named "dataPoint" in the capabilities.json (showing only necessary blocks, the rest are removed on the screenshot).
2. I drag some data into the bucket named "Color saturation". metadata.objects looks like on the screenshot #2. As expected, "dataPoint" object is there, and everything works fine so far.
3. Then I save the report and reopen it by refreshing the page. Now "dataPoint" is absent in the "objects", so I can't retrieve the data I need and color saturation is not applied to items. I assume this is the bug.
https://github.com/Microsoft/powerbi-visuals-enhancedscatter
This custom visual has the same problem with color saturation.