id,node_id,number,title,user,state,locked,assignee,milestone,comments,created_at,updated_at,closed_at,author_association,active_lock_reason,draft,pull_request,body,reactions,performed_via_github_app,state_reason,repo,type
1020282789,I_kwDOAMm_X8480Eel,5843,Why are `da.chunks` and `ds.chunks` properties inconsistent?,35968931,closed,0,,,6,2021-10-07T17:21:01Z,2021-10-29T18:12:22Z,2021-10-29T18:12:22Z,MEMBER,,,,"Basically the title, but what I'm referring to is this:

```python
In [2]: da = xr.DataArray([[0, 1], [2, 3]], name='foo').chunk(1)

In [3]: ds = da.to_dataset()

In [4]: da.chunks
Out[4]: ((1, 1), (1, 1))

In [5]: ds.chunks
Out[5]: Frozen({'dim_0': (1, 1), 'dim_1': (1, 1)})
```

Why does `DataArray.chunks` return a tuple and `Dataset.chunks` return a frozen dictionary?

This seems a bit silly, for a few reasons:

1) it means that some perfectly reasonable code might fail unnecessarily if passed a DataArray instead of a Dataset or vice versa, such as

    ```python
    def is_core_dim_chunked(obj, core_dim):
        return len(obj.chunks[core_dim]) > 1
    ```
    which will work as intended for a dataset but raises a `TypeError` for a dataarray.

2) it breaks the pattern we use for `.sizes`, where

    ```python
    In [14]: da.sizes
    Out[14]: Frozen({'dim_0': 2, 'dim_1': 2})

    In [15]: ds.sizes
    Out[15]: Frozen({'dim_0': 2, 'dim_1': 2})
    ```

3) if you want the chunks as a tuple they are always accessible via `da.data.chunks`, which is a more sensible place to look to find the chunks without dimension names.

4) It's an undocumented difference, as the docstrings for `ds.chunks` and `da.chunks` both only say

    `""""""Block dimensions for this dataset’s data or None if it’s not a dask array.""""""`
    
    which doesn't tell me anything about the return type, or warn me that the return types are different.
    
    EDIT: In fact `DataArray.chunk` doesn't even appear to be listed on the API docs page at all.


In our codebase this difference is mostly washed out by us using `._to_temp_dataset()` all the time, and also by the way that the `.chunk()` method accepts both the tuple and dict form, so both of these invariants hold (but in different ways):

```
ds == ds.chunk(ds.chunks)
da == da.chunk(da.chunks)
```




I'm not sure whether making this consistent is worth the effort of a significant breaking change though :confused:

(Sort of related to https://github.com/pydata/xarray/issues/2103)","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/5843/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,completed,13221727,issue