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
1160062673,I_kwDOAMm_X85FJSbR,6333,Expressing dimension's preferred chunks as tuple of integers causes TypeError,38358698,closed,0,,,0,2022-03-04T21:23:21Z,2022-04-08T17:18:50Z,2022-04-08T17:18:50Z,CONTRIBUTOR,,,,"### What happened?

When opening a dataset containing a variable that has preferred chunks expressed along some dimension as a tuple of integers, *xarray* raises a `TypeError`.

### What did you expect to happen?

I expected to open the dataset with its preferred chunks, as described in the documentation on preferred chunks within ""How to add a new backend"".

### Minimal Complete Verifiable Example

```Python
import xarray as xr

class PassThroughBackendEntrypoint(xr.backends.BackendEntrypoint):
    def open_dataset(self, dataset, *, drop_variables=None):
        return dataset

initial = xr.Dataset(
    {
        ""data"": xr.Variable(
            (""dim"",), [0, 0], encoding={""preferred_chunks"": {""dim"": (1, 1)}}
        )
    }
)
final = xr.open_dataset(initial, engine=PassThroughBackendEntrypoint, chunks={})
```


### Relevant log output

```Python
[Paths simplified.]

Traceback (most recent call last):
  File ""<stdin>"", line 1, in <module>
  File ""...\xarray\backends\api.py"", line 501, in open_dataset
    ds = _dataset_from_backend_dataset(
  File ""...\xarray\backends\api.py"", line 317, in _dataset_from_backend_dataset
    ds = _chunk_ds(
  File ""...\xarray\backends\api.py"", line 287, in _chunk_ds
    var_chunks = _get_chunk(var, chunks)
  File ""...\xarray\core\dataset.py"", line 409, in _get_chunk

    _check_chunks_compatibility(var, output_chunks, preferred_chunks)
  File ""...\xarray\core\dataset.py"", line 371, in _check_chunks_compatibility
    if any(s % preferred_chunks_dim for s in chunks_dim):
  File ""...\xarray\core\dataset.py"", line 371, in <genexpr>
    if any(s % preferred_chunks_dim for s in chunks_dim):
TypeError: unsupported operand type(s) for %: 'int' and 'tuple'
```


### Anything else we need to know?

The behavior exhibited above touches on the following related issues:

*   The `_check_chunks_compatibility` function assumes that a dimension expresses its preferred chunks only as an integer, not a sequence of integers.  In contrast, *Dask* will handle either within the `previous_chunks` argument to its `normalize_chunks` function.

*   The examples in the documentation of `""preferred_chunks""` mappings, namely `{“dim1”: 1000, “dim2”: 2000}` and `{“dim1”: [1000, 100], “dim2”: [2000, 2000, 2000]]}`, have syntax errors: The quotation marks are curly instead of straight, and the second example has an extra closing bracket.

*   After correcting the syntax errors, the lists in the second example lead to `TypeError: unhashable type: 'list'`.  *Dask* raises the exception when it tries to test a mutable list for set membership, as in the following (with simplified paths):

    ```python
    >>> dask.array.core.normalize_chunks([[1000, 100], [2000, 2000, 2000]], (1100, 6000))
    Traceback (most recent call last):
      File ""<stdin>"", line 1, in <module>
      File ""...\dask\array\core.py"", line 2900, in normalize_chunks
        chunks = tuple(c if c not in {None, -1} else s for c, s in zip(chunks, shape))
      File ""...\dask\array\core.py"", line 2900, in <genexpr>
        chunks = tuple(c if c not in {None, -1} else s for c, s in zip(chunks, shape))
    TypeError: unhashable type: 'list'
    ```

    If one omits the second argument (the shape) to that call, it succeeds.  This may be a bug in *Dask*.

*   The tests in *xarray* don't exercise behaviors related to preferred chunks.

[Edited for grammar.]

### Environment

```
INSTALLED VERSIONS
------------------
commit: None
python: 3.8.12 | packaged by conda-forge | (default, Oct 12 2021, 21:22:46) [MSC v.1916 64 bit (AMD64)]
python-bits: 64
OS: Windows
OS-release: 10
machine: AMD64
processor: Intel64 Family 6 Model 94 Stepping 3, GenuineIntel
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: ('English_United States', '1252')
libhdf5: 1.12.1
libnetcdf: 4.8.1

xarray: 0.20.3.dev52+gd3b6aa6d
pandas: 1.4.1
numpy: 1.21.5
scipy: 1.8.0
netCDF4: 1.5.8
pydap: installed
h5netcdf: 0.13.1
h5py: 3.6.0
Nio: None
zarr: 2.11.0
cftime: 1.5.2
nc_time_axis: 1.4.0
PseudoNetCDF: installed
rasterio: 1.2.10
cfgrib: None
iris: 3.2.0.post0
bottleneck: 1.3.2
dask: 2022.02.0
distributed: 2022.02.0
matplotlib: 3.5.1
cartopy: 0.20.2
seaborn: 0.11.2
numbagg: 0.2.1
fsspec: 2022.01.0
cupy: None
pint: 0.18
sparse: 0.13.0
setuptools: 59.8.0
pip: 22.0.3
conda: None
pytest: 7.0.1
IPython: None
sphinx: None
```","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/6333/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,completed,13221727,issue
1160073438,PR_kwDOAMm_X84z-iqi,6334,"In backends, support expressing a dimension's preferred chunk sizes as a tuple of integers",38358698,closed,0,,,5,2022-03-04T21:39:46Z,2022-04-08T17:18:50Z,2022-04-08T17:18:50Z,CONTRIBUTOR,,0,pydata/xarray/pulls/6334,"- [X] Closes #6333
- [X] Tests added
- [X] User visible changes (including notable bug fixes) are documented in `whats-new.rst`
","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/6334/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,pull
1159961396,PR_kwDOAMm_X84z-K39,6330,"In documentation on adding a new backend, add missing import and tweak headings",38358698,closed,0,,,0,2022-03-04T19:13:30Z,2022-03-07T14:17:29Z,2022-03-07T13:13:50Z,CONTRIBUTOR,,0,pydata/xarray/pulls/6330,"Adding the import resolves the following exception that *sphinx-build* raises when one builds only ""doc/internals/how-to-add-new-backend.rst"":

```
NameError                                 Traceback (most recent call last)
Input In [1], in <module>
----> 1 var = xr.Variable(
      2     dims=(""x"",), data=np.arange(10.0), attrs={""scale_factor"": 10, ""add_offset"": 2}
      3 )

NameError: name 'xr' is not defined
```

While in the file, I revised headings to have only their first letter capitalized (except for case-sensitive code), which seems to be the majority convention in the documentation.","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/6330/reactions"", ""total_count"": 2, ""+1"": 2, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,pull
1124431593,PR_kwDOAMm_X84yGFBx,6237,Enable running sphinx-build on Windows,38358698,closed,0,,,7,2022-02-04T17:15:14Z,2022-03-04T19:15:42Z,2022-03-01T16:00:34Z,CONTRIBUTOR,,0,pydata/xarray/pulls/6237,"- [x] User visible changes (including notable bug fixes) are documented in `whats-new.rst`

This PR enables one to build the documentation on Windows by manually invoking `sphinx-build`.

The first commit enables *sphinx* to execute the ""conf.py"" file. Before the commit, *sphinx* complains:

```
Configuration error:
There is a programmable error in your configuration file:
```

with the exception `FileNotFoundError: [WinError 2] The system cannot find the file specified` where it tries to invoke *conda*. On Windows, *conda* environments other than the base environment have ""conda.bat"" on their path rather than ""conda.exe"", and one must call `subprocess.run` with ""conda.bat"" instead of merely ""conda"". However, the `CONDA_EXE` environment variable correctly points to the executable and should do so across platforms; it requires *conda* version 4.5 or later for conda/conda#6923.

The second commit enables the build to tolerate exceptions when deleting temporary files and tells Git to ignore more such files. Without the commit, builds occasionally failed at the `os.remove` calls with exceptions such as `PermissionError: [WinError 32] The process cannot access the file because it is being used by another process: 'example.nc'`.

Should ""whats-new.rst"" mention these changes, which are developer-visible but not user-visible?

I welcome any feedback.

Edit: Checked the ""whats-new"" task.","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/6237/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,pull
1158639113,PR_kwDOAMm_X84z5zPC,6326,"Lengthen underline, correct spelling, and reword",38358698,closed,0,,,1,2022-03-03T16:40:55Z,2022-03-03T17:27:42Z,2022-03-03T17:01:15Z,CONTRIBUTOR,,0,pydata/xarray/pulls/6326,"Lengthening the underline resolves the following warning from *sphinx-build*:

```
[...]\xarray\doc\whats-new.rst:20: WARNING: Title underline too short.

v2022.03.1 (unreleased)
---------------------
```","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/6326/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,pull
1150484906,PR_kwDOAMm_X84zd6WA,6305,"On Windows, enable successful test of opening a dataset containing a cftime index",38358698,closed,0,,,3,2022-02-25T14:07:50Z,2022-02-28T16:06:33Z,2022-02-28T09:53:22Z,CONTRIBUTOR,,0,pydata/xarray/pulls/6305,"- [X] User visible changes (including notable bug fixes) are documented in `whats-new.rst`

Previously, on Windows, the subject test unnecessarily failed, and the temporary directory and file remained, because the scheduler in the outer context prevented deleting the temporary directory upon exiting the inner context of the latter.

<details><summary>Example failure (with short traceback):</summary>
<p>

```
================================================ FAILURES =================================================
__________________________ test_open_mfdataset_can_open_files_with_cftime_index ___________________________
C:\Users\stan.west\Programs\Miniconda3-64\envs\xarray-dev\lib\shutil.py:616: in _rmtree_unsafe
    os.unlink(fullname)
E   PermissionError: [WinError 32] The process cannot access the file because it is being used by another process: 'C:\\Users\\STAN~1.WES\\AppData\\Local\\Temp\\tmpdpdajrgc\\test.nc'

During handling of the above exception, another exception occurred:
C:\Users\stan.west\Programs\Miniconda3-64\envs\xarray-dev\lib\tempfile.py:802: in onerror
    _os.unlink(path)
E   PermissionError: [WinError 32] The process cannot access the file because it is being used by another process: 'C:\\Users\\STAN~1.WES\\AppData\\Local\\Temp\\tmpdpdajrgc\\test.nc'

During handling of the above exception, another exception occurred:
C:\Users\stan.west\Documents\Repositories\xarray\xarray\tests\test_distributed.py:128: in test_open_mfdataset_can_open_files_with_cftime_index
    assert_identical(tf[""test""], da)
C:\Users\stan.west\Programs\Miniconda3-64\envs\xarray-dev\lib\tempfile.py:827: in __exit__
    self.cleanup()
C:\Users\stan.west\Programs\Miniconda3-64\envs\xarray-dev\lib\tempfile.py:831: in cleanup
    self._rmtree(self.name)
C:\Users\stan.west\Programs\Miniconda3-64\envs\xarray-dev\lib\tempfile.py:813: in _rmtree
    _shutil.rmtree(name, onerror=onerror)
C:\Users\stan.west\Programs\Miniconda3-64\envs\xarray-dev\lib\shutil.py:740: in rmtree
    return _rmtree_unsafe(path, onerror)
C:\Users\stan.west\Programs\Miniconda3-64\envs\xarray-dev\lib\shutil.py:618: in _rmtree_unsafe
    onerror(os.unlink, fullname, sys.exc_info())
C:\Users\stan.west\Programs\Miniconda3-64\envs\xarray-dev\lib\tempfile.py:805: in onerror
    cls._rmtree(path)
C:\Users\stan.west\Programs\Miniconda3-64\envs\xarray-dev\lib\tempfile.py:813: in _rmtree
    _shutil.rmtree(name, onerror=onerror)
C:\Users\stan.west\Programs\Miniconda3-64\envs\xarray-dev\lib\shutil.py:740: in rmtree
    return _rmtree_unsafe(path, onerror)
C:\Users\stan.west\Programs\Miniconda3-64\envs\xarray-dev\lib\shutil.py:599: in _rmtree_unsafe
    onerror(os.scandir, path, sys.exc_info())
C:\Users\stan.west\Programs\Miniconda3-64\envs\xarray-dev\lib\shutil.py:596: in _rmtree_unsafe
    with os.scandir(path) as scandir_it:
E   NotADirectoryError: [WinError 267] The directory name is invalid: 'C:\\Users\\STAN~1.WES\\AppData\\Local\\Temp\\tmpdpdajrgc\\test.nc'
========================================= short test summary info =========================================
FAILED xarray/tests/test_distributed.py::test_open_mfdataset_can_open_files_with_cftime_index - NotADirec...

=========================================== 1 failed in 10.77s ============================================
```

</p>
</details>

The first commit swaps the two contexts to resolve the issue. The second commit replaces the `tempfile.TemporaryDirectory()` context manager with *pytest*'s `tmp_path` fixture, which slightly simplifies the test and relies on *pytest* to remove the directory on a subsequent invocation.","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/6305/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,pull
769348008,MDU6SXNzdWU3NjkzNDgwMDg=,4702,Plotting in 2D with one non-dimension coordinate given behaves contrary to documentation and can cause cryptic ValueError,38358698,open,0,,,2,2020-12-16T23:33:25Z,2020-12-17T18:35:13Z,,CONTRIBUTOR,,,,"**What happened**:

I called a 2-D plot method with one coordinate specified as a non-dimension coordinate through the `x` or `y` argument. The method raised a `ValueError` that complained about a tuple of duplicate coordinates that I had not provided.

Also, when I specified `x` and omitted `y`, the method took `y` to be the second dimension of the `DataArray`.


**What you expected to happen**:

I expected the unspecified `x` or `y` argument to behave as when I specified neither argument, so that, for a suitable `DataArray` `da`, calling `da.plot(x=""lon"")` would have the same *Y* axis as `da.plot()`. That expectation is consistent with the docstring common to 2-D plotting methods, where the default values for the `x` and `y` arguments are `da.dims[1]` and `da.dims[0]`, respectively. However, as discussed below, the docstring does not mention that *xarray* tries to guess the omitted coordinate.


**Minimal Complete Verifiable Example**:

Executing

```python
import numpy as np
import xarray as xr

da = xr.DataArray(
    np.arange(20).reshape(4, 5),
    dims=(""v"", ""u""),
    coords={""lat"": (""v"", np.linspace(0, 30, 4)), ""lon"": (""u"", np.linspace(-20, 20, 5))},
)
da.plot(x=""lon"")
```

causes (with file paths abbreviated)

```
Traceback (most recent call last):
  File ""<stdin>"", line 1, in <module>
  File ""...\xarray\plot\plot.py"", line 446, in __call__
    return plot(self._da, **kwargs)
  File ""...\xarray\plot\plot.py"", line 200, in plot
    return plotfunc(darray, **kwargs)
  File ""...\xarray\plot\plot.py"", line 707, in newplotfunc
    darray = darray.transpose(*dims, transpose_coords=True)
  File ""...\xarray\core\dataarray.py"", line 2036, in transpose
    dims = tuple(utils.infix_dims(dims, self.dims))
  File ""...\xarray\core\utils.py"", line 725, in infix_dims
    raise ValueError(
ValueError: ('u', 'u') must be a permuted list of ('v', 'u'), unless `...` is included
```

Executing `da.plot(y=""lon"")` causes the same exception.


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

Two aspects of this issue that I see are the behavior and the documentation.

The behavior in the above example involves *xarray* trying to guess the other dimension [#1291 in v. 0.9.2]. The [guessing logic](https://github.com/pydata/xarray/blob/778a16ef392edd13cd14e1548700842e53e4656f/xarray/plot/utils.py#L379-L384) tests whether the given coordinate equals one of the array's dimension names; here, the given coordinate is a non-dimension coordinate and fails to match. When the match fails, the other coordinate is set to the second dimension, whether the given coordinate was `x` or `y`. One possible improvement would be to set the `y` coordinate to the first dimension instead, as in the following replacement for the last line of the guessing logic:

```python
y = darray.dims[1] if x == darray.dims[0] else darray.dims[0]
```

With that change, `da.plot(x=""lon"")` and `da.plot(y=""lat"")` would succeed and produce the plots I expect, while `da.plot(x=""lat"")` and `da.plot(y=""lon"")` would raise `ValueError`. Also, I would find it more helpful if the exception message were more clearly related to the arguments of the call. The `_infer_xy_labels` function might need to notice that it was about to set `x` and `y` to the same dimension name and raise an exception at that point.

The [documentation](https://github.com/pydata/xarray/blob/778a16ef392edd13cd14e1548700842e53e4656f/xarray/plot/plot.py#L486-L489) seems not to have been updated for #1291 and does not mention the guessing behavior.

**Environment**:

<details><summary>Output of <tt>xr.show_versions()</tt></summary>

```
INSTALLED VERSIONS
------------------
commit: None
python: 3.8.5 (default, Sep  3 2020, 21:29:08) [MSC v.1916 64 bit (AMD64)]
python-bits: 64
OS: Windows
OS-release: 10
machine: AMD64
processor: Intel64 Family 6 Model 94 Stepping 3, GenuineIntel
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: English_United States.1252
libhdf5: 1.10.4
libnetcdf: 4.7.3

xarray: 0.16.1
pandas: 1.1.3
numpy: 1.19.2
scipy: None
netCDF4: 1.5.3
pydap: None
h5netcdf: 0.8.1
h5py: 2.10.0
Nio: None
zarr: None
cftime: 1.3.0
nc_time_axis: None
PseudoNetCDF: None
rasterio: None
cfgrib: None
iris: None
bottleneck: None
dask: 2.30.0
distributed: 2.30.1
matplotlib: 3.3.2
cartopy: None
seaborn: None
numbagg: None
pint: None
setuptools: 50.3.0.post20201006
pip: 20.2.4
conda: None
pytest: None
IPython: 7.18.1
sphinx: None
```
</details>","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/4702/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,issue