T371924: Allow chart definitions and tabular data to be loaded from Commons enabled us to configure a wiki such that Data:.chart pages or Data:.tab pages (or both) are loaded from a remote wiki. In production, we intend to use this to load these pages from Commons.
However, we don't currently have fallback functionality: if the wiki is configured to load .chart pages from Commons, and the requested .chart page doesn't exist on Commons, we'll display an error, even if a .chart page by that name does exist on the local wiki. This is in contrast to how images work, where both remote images from Commons and local images on the wiki itself can be used (and if both exist, the local image takes precedence).
We should consider whether we want to implement that behavior for charts, or whether we want to stick with the current behavior (where each wiki can either load .chart/.tab files locally, or remotely, but not both).
Product questions to consider:
- Does it make sense to even allow local .chart/.tab page to be created on non-Commons wikis?
- If both a local .chart/.tab page and one on Commons exist with the same name, which one should be used?
Engineering questions to consider:
- How would we implement this behavior? Would we have to change things in the JsonConfig extension to make this work?
- If a page refers to a remote .chart/.tab page, but then a local page is created by that same name, would we re-render that page to reflect the fact that it now points to the local page instead of the remote page? How would we find out that that needs to happen?