Can fallback data types have fallbacks?

[clbarnes]

The spec currently allows fallback data types to either be core or extension data types, but disallows the "fallback" field in an extension data type object. If fallbacks are not limited to core types, why not allow further fallbacks?

[jbms]

The spec does say that fallback may be a list of data types:

zarr-specs/docs/v3/core/v3.0.rst

Line 494 in cdf97c9

if provided, its value must be one or a list of the data type identifiers

Note though, that in regard to fallback data types, there is an outstanding issue of how to deal with the fill value:
#236 (comment)

[clbarnes]

Ah, my fault for missing that! I suppose it's just an API decision of a single recursive approach or two very similar APIs.