mode=r+: Cannot write to read-only ZArray

[tbenst]

This fails:

p = "/tmp/example.zarr"
z1 = zcreate(Int, 10000, 10000, path = p, chunks = (1000, 1000))
z1[1, :] = 1:10000
mode = "r+"
z2 = zopen(p,mode)
z2[1,2] = 42
z1[1,1:3]

This also fails for mode="a" or mode="a+", but works on mode="w". Unfortunately, I cannot use mode="w" as I do not wish to truncate the file, but rather re-open an existing Zarr array for modification. On testing, it appears that mode="w" does not actually truncate the .zarr directory, which I believe conflicts with julia's definition for open modes / is inconsistent with python Zarr.

Much appreciate your efforts to bring Zarr to Julia!

[meggart]

Sorry for this, this is definitely bad documentation/implementation. Mode "w" does not truncate but is actually equivalent to "a". When originally implementing this I was following the mental model of NetCDF modes and only made a difference between Read-only and Read/Write modes and just called them "r" and "w" without thinking a lot.

Yes, we should fix this, but this will be breaking in a very nasty way, when silently changing the behavior of "w" to actually truncate the file while in the past it meant "append". So I would suggest to have a full deprecation cycle on this... Will think about it a bit, but please suggest solutions in case you have ideas.

[tbenst]

Ah, thank you! Good to know that I can use “w” for now. Full deprecation cycle makes sense, and perhaps useful to add “a” as an alias in meantime