issues: 2105703882

What happened?

ds.weighted(weights).mean(dims) errors when reducing over a dimension that is neither on the weights nor on the variable.

What did you expect to happen?

This used to work and was "broken" by #8606. However, we may want to fix this by ignoring (?) those data vars instead (#7027).

Minimal Complete Verifiable Example

```Python import xarray as xr

ds = xr.Dataset({"a": (("y", "x"), [[1, 2]]), "scalar": 1}) weights = xr.DataArray([1, 2], dims="x")

ds.weighted(weights).mean("y") ```

MVCE confirmation

• [ ] Minimal example — the example is as focused as reasonably possible to demonstrate the underlying issue in xarray.
• [ ] Complete example — the example is self-contained, including all data and the text of any traceback.
• [ ] Verifiable example — the example copy & pastes into an IPython prompt or Binder notebook, returning the result.
• [ ] New issue — a search of GitHub Issues suggests this is not a duplicate.
• [ ] Recent environment — the issue occurs with the latest version of xarray and its dependencies.

Relevant log output

```Python ValueError Traceback (most recent call last) Cell In[1], line 6 3 ds = xr.Dataset({"a": (("y", "x"), [[1, 2]]), "scalar": 1}) 4 weights = xr.DataArray([1, 2], dims="x") ----> 6 ds.weighted(weights).mean("y")

File ~/code/xarray/xarray/util/deprecation_helpers.py:115, in _deprecate_positional_args.<locals>._decorator.<locals>.inner(args, kwargs) 111 kwargs.update({name: arg for name, arg in zip_args}) 113 return func(args[:-n_extra_args], kwargs) --> 115 return func(*args, kwargs)

File ~/code/xarray/xarray/core/weighted.py:497, in Weighted.mean(self, dim, skipna, keep_attrs) 489 @_deprecate_positional_args("v2023.10.0") 490 def mean( 491 self, (...) 495 keep_attrs: bool | None = None, 496 ) -> T_Xarray: --> 497 return self._implementation( 498 self._weighted_mean, dim=dim, skipna=skipna, keep_attrs=keep_attrs 499 )

File ~/code/xarray/xarray/core/weighted.py:558, in DatasetWeighted._implementation(self, func, dim, kwargs) 555 def _implementation(self, func, dim, kwargs) -> Dataset: 556 self._check_dim(dim) --> 558 return self.obj.map(func, dim=dim, **kwargs)

File ~/code/xarray/xarray/core/dataset.py:6924, in Dataset.map(self, func, keep_attrs, args, kwargs) 6922 if keep_attrs is None: 6923 keep_attrs = _get_keep_attrs(default=False) -> 6924 variables = { 6925 k: maybe_wrap_array(v, func(v, *args, kwargs)) 6926 for k, v in self.data_vars.items() 6927 } 6928 if keep_attrs: 6929 for k, v in variables.items():

File ~/code/xarray/xarray/core/dataset.py:6925, in <dictcomp>(.0) 6922 if keep_attrs is None: 6923 keep_attrs = _get_keep_attrs(default=False) 6924 variables = { -> 6925 k: maybe_wrap_array(v, func(v, args, *kwargs)) 6926 for k, v in self.data_vars.items() 6927 } 6928 if keep_attrs: 6929 for k, v in variables.items():

File ~/code/xarray/xarray/core/weighted.py:286, in Weighted._weighted_mean(self, da, dim, skipna) 278 def _weighted_mean( 279 self, 280 da: T_DataArray, 281 dim: Dims = None, 282 skipna: bool | None = None, 283 ) -> T_DataArray: 284 """Reduce a DataArray by a weighted mean along some dimension(s).""" --> 286 weighted_sum = self._weighted_sum(da, dim=dim, skipna=skipna) 288 sum_of_weights = self._sum_of_weights(da, dim=dim) 290 return weighted_sum / sum_of_weights

File ~/code/xarray/xarray/core/weighted.py:276, in Weighted._weighted_sum(self, da, dim, skipna) 268 def _weighted_sum( 269 self, 270 da: T_DataArray, 271 dim: Dims = None, 272 skipna: bool | None = None, 273 ) -> T_DataArray: 274 """Reduce a DataArray by a weighted sum along some dimension(s).""" --> 276 return self._reduce(da, self.weights, dim=dim, skipna=skipna)

File ~/code/xarray/xarray/core/weighted.py:231, in Weighted._reduce(da, weights, dim, skipna) 227 da = da.fillna(0.0) 229 # dot does not broadcast arrays, so this avoids creating a large 230 # DataArray (if weights has additional dimensions) --> 231 return dot(da, weights, dim=dim)

File ~/code/xarray/xarray/util/deprecation_helpers.py:140, in deprecate_dims.<locals>.wrapper(args, kwargs) 132 emit_user_level_warning( 133 "The dims argument has been renamed to dim, and will be removed " 134 "in the future. This renaming is taking place throughout xarray over the " (...) 137 PendingDeprecationWarning, 138 ) 139 kwargs["dim"] = kwargs.pop("dims") --> 140 return func(args, **kwargs)

File ~/code/xarray/xarray/core/computation.py:1885, in dot(dim, arrays, *kwargs) 1883 dim = tuple(d for d, c in dim_counts.items() if c > 1) 1884 else: -> 1885 dim = parse_dims(dim, all_dims=tuple(all_dims)) 1887 dot_dims: set[Hashable] = set(dim) 1889 # dimensions to be parallelized

File ~/code/xarray/xarray/core/utils.py:1046, in parse_dims(dim, all_dims, check_exists, replace_none) 1044 dim = (dim,) 1045 if check_exists: -> 1046 _check_dims(set(dim), set(all_dims)) 1047 return tuple(dim)

File ~/code/xarray/xarray/core/utils.py:1131, in _check_dims(dim, all_dims) 1129 if wrong_dims: 1130 wrong_dims_str = ", ".join(f"'{d!s}'" for d in wrong_dims) -> 1131 raise ValueError( 1132 f"Dimension(s) {wrong_dims_str} do not exist. Expected one or more of {all_dims}" 1133 )

ValueError: Dimension(s) 'y' do not exist. Expected one or more of {'x'} ```

Anything else we need to know?

No response

Environment

Newest main (i.e. 2024.01)