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
665023246,MDU6SXNzdWU2NjUwMjMyNDY=,4263,apply_ufunc does not pass block_info to the applied function,1649961,closed,0,,,2,2020-07-24T08:53:51Z,2021-10-18T16:11:28Z,2021-10-18T16:11:28Z,NONE,,,,"<!-- Please include a self-contained copy-pastable example that generates the issue if possible.

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**What happened**:

`xarray.apply_ufunc` does not pass `block_info` to the applied function when `dask=""parallelized""`.

**What you expected to happen**:

The applied function gets the special `block_info` argument (see the [`map_blocks`](https://docs.dask.org/en/latest/array-api.html#dask.array.map_blocks) documentation).

**Minimal Complete Verifiable Example**:

```python
import sys

import dask.array
import xarray


def f(a, block_info=None):
    loc = None if block_info is None else block_info[None][""chunk-location""]
    sys.stdout.write(f""chunk-location={loc}\n"")
    return a


a = xarray.DataArray(dask.array.arange(24).reshape((4, 6)).rechunk((2, 3)), dims=(""a"", ""b""))
meta = dask.array.empty((0,), dtype=a.dtype)

xarray.apply_ufunc(f, a, dask=""parallelized"", output_dtypes=[a.dtype], meta=meta).compute();
# chunk-location=None
# chunk-location=None
# chunk-location=None
# chunk-location=None

dask.array.map_blocks(f, a.data, dtype=a.dtype, meta=meta).compute();
# chunk-location=(0, 0)
# chunk-location=(0, 1)
# chunk-location=(1, 0)
# chunk-location=(1, 1)
```

**Anything else we need to know?**:

It seems that `xarray.apply_ufunc` calls `dask.array.blockwise` [directly](https://github.com/pydata/xarray/blob/349c5960f2008099ec99223b005df6552d3f85f9/xarray/core/computation.py#L725), while `block_info` is [handled](https://github.com/dask/dask/blob/024f690b6d269c11a496db088c4ddd8d5de12a49/dask/array/core.py#L660) by `dask.array.map_blocks`.

**Environment**:

<details><summary>Output of <tt>xr.show_versions()</tt></summary>
<pre>
INSTALLED VERSIONS
------------------
commit: None
python: 3.7.7 (default, May  6 2020, 04:59:01) 
[Clang 4.0.1 (tags/RELEASE_401/final)]
python-bits: 64
OS: Darwin
OS-release: 19.5.0
machine: x86_64
processor: i386
byteorder: little
LC_ALL: None
LANG: None
LOCALE: en_GB.UTF-8
libhdf5: 1.10.6
libnetcdf: None
xarray: 0.16.0
pandas: 1.0.5
numpy: 1.18.5
scipy: 1.5.0
netCDF4: None
pydap: None
h5netcdf: None
h5py: 2.10.0
Nio: None
zarr: 2.3.2
cftime: None
nc_time_axis: None
PseudoNetCDF: None
rasterio: None
cfgrib: None
iris: None
bottleneck: None
dask: 2.20.0
distributed: 2.20.0
matplotlib: 3.2.2
cartopy: None
seaborn: None
numbagg: None
pint: None
setuptools: 49.2.0.post20200714
pip: 20.1.1
conda: None
pytest: 5.4.3
IPython: 7.16.1
sphinx: 3.1.1
</pre>
</details>
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