`rectilinear` vs `rectangular` chunk grid names

[ianhi]

Problem

The current variable shaped chunk grids use rectilinear as their chunk grid metadata

zarr-python/src/zarr/core/metadata/v3.py

Lines 315 to 321 in 0ea15fd

	return {
	"name": "rectilinear",
	"configuration": {
	"kind": "inline",
	"chunk_shapes": tuple(serialized_dims),
	},
	}

however the ZEP https://zarr.dev/zeps/draft/ZEP0003.html#detailed-description

proposes

{
  "type": "rectangular", 
  "chunk_shape": [[5, 5, 5, 15, 15, 20, 35], 10],
  "separator":"/"
}

there are other differences as well - type vs name, chunk_shape vs chunk_shapes where the metadata is flat vs nested.

This makes it confusing to support downstream (icechunk).

Solution

one of zarr-python or the ZEP should be updated. I would suggest updating the ZEP to match the lessons learned from actual implementation.

[d-v-b]

our rectilinear chunk grid is not based on that zep. it's based on the spec here: https://github.com/zarr-developers/zarr-extensions/tree/main/chunk-grids/rectilinear