Issue using `tiff_to_zarr`

Hi there @martindurant,

I've started playing around with Kerchunk's tiff_to_zarr functionality and ran into an issue when trying to open up the reference file. In short, the tiff_to_zarr works successfully, but I get the error: ContainsArrayError: path '' contains an array. Hopefully this is a simple user error!
I've successfully used tiff_to_zarr on the kerchunk/tests/lcmap_tiny_cog_2019.tif and this Arctic DEM without incident.

Thanks in advance!

I've included a code snippet below and a example of the generated reference file.

Generation script:

import fsspec
import xarray as xr
import ujson
import imagecodecs.numcodecs
imagecodecs.numcodecs.register_codecs()

from kerchunk.tiff import tiff_to_zarr

hansen_url = 'https://storage.googleapis.com/earthenginepartners-hansen/GFC-2021-v1.9/Hansen_GFC-2021-v1.9_gain_50N_130W.tif'
ex_path = 'https://github.com/fsspec/kerchunk/blob/main/kerchunk/tests/lcmap_tiny_cog_2019.tif?raw=true'

hansen_ds = xr.open_dataset(hansen_url,engine='rasterio')


ex_ds = xr.open_dataset(ex_path,engine='rasterio')



zt = tiff_to_zarr(hansen_url)
with open("hansen.json", "wb") as f:
    f.write(ujson.dumps(zt).encode())

m = fsspec.get_mapper("reference://", fo='hansen.json')
hansen_kerchunk_ds = xr.open_dataset(
    m, engine="zarr", backend_kwargs={"consolidated": False}
)

examples of refs for both datasets:

Hansen:

{
	".zattrs": "{\"_ARRAY_DIMENSIONS\":[\"Y\",\"X\"],\"KeyDirectoryVersion\":1,\"KeyRevision\":1,\"KeyRevisionMinor\":0,\"GTModelTypeGeoKey\":2,\"GTRasterTypeGeoKey\":1,\"GeographicTypeGeoKey\":4326,\"GeogCitationGeoKey\":\"WGS 84\",\"GeogAngularUnitsGeoKey\":9102,\"GeogSemiMajorAxisGeoKey\":6378137.0,\"GeogInvFlatteningGeoKey\":298.257223563,\"ModelPixelScale\":[0.00025,0.00025,0.0],\"ModelTiepoint\":[0.0,0.0,0.0,-130.0,50.0,0.0]}",
	".zarray": "{\n \"chunks\": [\n  1,\n  40000\n ],\n \"compressor\": {\n  \"id\": \"imagecodecs_lzw\"\n },\n \"dtype\": \"|u1\",\n \"fill_value\": 0,\n \"filters\": null,\n \"order\": \"C\",\n \"shape\": [\n  40000,\n  40000\n ],\n \"zarr_format\": 2\n}",
	"0.0": ["https:\/\/storage.googleapis.com\/earthenginepartners-hansen\/GFC-2021-v1.9\/Hansen_GFC-2021-v1.9_gain_50N_130W.tif", 320378, 777],
	"1.0": ["https:\/\/storage.googleapis.com\/earthenginepartners-hansen\/GFC-2021-v1.9\/Hansen_GFC-2021-v1.9_gain_50N_130W.tif", 321155, 796], ...}

Kerchunk test tiff:

{
	".zgroup": "{\n \"zarr_format\": 2\n}",
	".zattrs": "{\"multiscales\":[{\"datasets\":[{\"path\":\"0\"},{\"path\":\"1\"},{\"path\":\"2\"}],\"metadata\":{},\"name\":\"\",\"version\":\"0.1\"}],\"OVR_RESAMPLING_ALG\":\"NEAREST\",\"LAYOUT\":\"IFDS_BEFORE_DATA\",\"BLOCK_ORDER\":\"ROW_MAJOR\",\"BLOCK_LEADER\":\"SIZE_AS_UINT4\",\"BLOCK_TRAILER\":\"LAST_4_BYTES_REPEATED\",\"KNOWN_INCOMPATIBLE_EDITION\":\"NO\",\"KeyDirectoryVersion\":1,\"KeyRevision\":1,\"KeyRevisionMinor\":0,\"GTModelTypeGeoKey\":1,\"GTRasterTypeGeoKey\":1,\"GTCitationGeoKey\":\"Albers\",\"GeographicTypeGeoKey\":4326,\"GeogCitationGeoKey\":\"WGS 84\",\"GeogAngularUnitsGeoKey\":9102,\"GeogSemiMajorAxisGeoKey\":6378140.0,\"GeogInvFlatteningGeoKey\":298.256999999996,\"ProjectedCSTypeGeoKey\":32767,\"ProjectionGeoKey\":32767,\"ProjCoordTransGeoKey\":11,\"ProjLinearUnitsGeoKey\":9001,\"ProjStdParallel1GeoKey\":29.5,\"ProjStdParallel2GeoKey\":45.5,\"ProjNatOriginLongGeoKey\":-96.0,\"ProjNatOriginLatGeoKey\":23.0,\"ProjFalseEastingGeoKey\":0.0,\"ProjFalseNorthingGeoKey\":0.0,\"ModelPixelScale\":[30.0,30.0,0.0],\"ModelTiepoint\":[0.0,0.0,0.0,-1801185.0,2700405.0,0.0]}",
	"0\/.zattrs": "{\n \"_ARRAY_DIMENSIONS\": [\n  \"Y\",\n  \"X\"\n ]\n}",
	"0\/.zarray": "{\n \"chunks\": [\n  512,\n  512\n ],\n \"compressor\": {\n  \"id\": \"zlib\"\n },\n \"dtype\": \"|u1\",\n \"fill_value\": 0,\n \"filters\": null,\n \"order\": \"C\",\n \"shape\": [\n  2048,\n  2048\n ],\n \"zarr_format\": 2\n}",
	"1\/.zattrs": "{\n \"_ARRAY_DIMENSIONS\": [\n  \"Y1\",\n  \"X1\"\n ]\n}",
	"1\/.zarray": "{\n \"chunks\": [\n  128,\n  128\n ],\n \"compressor\": {\n  \"id\": \"zlib\"\n },\n \"dtype\": \"|u1\",\n \"fill_value\": 0,\n \"filters\": null,\n \"order\": \"C\",\n \"shape\": [\n  1024,\n  1024\n ],\n \"zarr_format\": 2\n}",
	"2\/.zattrs": "{\n \"_ARRAY_DIMENSIONS\": [\n  \"Y2\",\n  \"X2\"\n ]\n}",
	"2\/.zarray": "{\n \"chunks\": [\n  128,\n  128\n ],\n \"compressor\": {\n  \"id\": \"zlib\"\n },\n \"dtype\": \"|u1\",\n \"fill_value\": 0,\n \"filters\": null,\n \"order\": \"C\",\n \"shape\": [\n  512,\n  512\n ],\n \"zarr_format\": 2\n}",
	"0\/0.0": ["https:\/\/github.com\/fsspec\/kerchunk\/blob\/main\/kerchunk\/tests\/lcmap_tiny_cog_2019.tif?raw=true", 114079, 13584],
	"0\/0.1": ["https:\/\/github.com\/fsspec\/kerchunk\/blob\/main\/kerchunk\/tests\/lcmap_tiny_cog_2019.tif?raw=true", 127671, 19626], ...}

repr's of both ref datasets:

---------------------------------------------------------------------------
ContainsArrayError                        Traceback (most recent call last)
Cell In[49], line 2
      1 m = fsspec.get_mapper("reference:[//](https://github.com/fsspec/kerchunk/issues/313)", fo='hansen.json')
----> 2 hansen_kerchunk_ds = xr.open_dataset(
      3     m, engine="zarr", backend_kwargs={"consolidated": False}
      4 )

File [~/opt/anaconda3/envs/install/envs/test_env/lib/python3.9/site-packages/xarray/backends/api.py:526](https://file+.vscode-resource.vscode-cdn.net/Users/nrhagen/Documents/carbonplan/global_forest_watch/~/opt/anaconda3/envs/install/envs/test_env/lib/python3.9/site-packages/xarray/backends/api.py:526), in open_dataset(filename_or_obj, engine, chunks, cache, decode_cf, mask_and_scale, decode_times, decode_timedelta, use_cftime, concat_characters, decode_coords, drop_variables, inline_array, backend_kwargs, **kwargs)
    514 decoders = _resolve_decoders_kwargs(
    515     decode_cf,
    516     open_backend_dataset_parameters=backend.open_dataset_parameters,
   (...)
    522     decode_coords=decode_coords,
    523 )
    525 overwrite_encoded_chunks = kwargs.pop("overwrite_encoded_chunks", None)
--> 526 backend_ds = backend.open_dataset(
    527     filename_or_obj,
    528     drop_variables=drop_variables,
    529     **decoders,
    530     **kwargs,
    531 )
    532 ds = _dataset_from_backend_dataset(
    533     backend_ds,
    534     filename_or_obj,
...
-> 1442             raise ContainsArrayError(path)
   1443         raise GroupNotFoundError(path)
   1445 elif mode == 'w':

ContainsArrayError: path '' contains an array

Start with the kerchunk.tiff.tiff_to_zarr entry point and reproduce the xarray.open_dataset call using the generated hansen.json reference. Compare its structure with the working lcmap_tiny_cog_2019.tif reference and trace the source of ContainsArrayError. Done means the reported reference opens successfully or the unsupported TIFF structure and expected behavior are clearly diagnosed.