Forbid invalid Coordinates object

xarray/core/coordinates.py

@@ -22,7 +22,11 @@
     assert_no_index_corrupted,
     create_default_index_implicit,
 )
-from xarray.core.merge import merge_coordinates_without_align, merge_coords
+from xarray.core.merge import (
+    assert_valid_explicit_coords,
+    merge_coordinates_without_align,
+    merge_coords,
+)
 from xarray.core.types import DataVars, Self, T_DataArray, T_Xarray
 from xarray.core.utils import (
     Frozen,
@@ -306,6 +310,11 @@ def __init__(
                 else:
                     variables[name] = var
 
+            dims = set(d for var in variables.values() for d in var.dims)
+            assert_valid_explicit_coords(
+                variables, dims=dims, explicit_coords=list(variables)
+            )
+
         if indexes is None:
             indexes = {}
         else:

xarray/core/merge.py

@@ -564,7 +564,7 @@ def merge_coords(
 
 def assert_valid_explicit_coords(
     variables: Mapping[Any, Any],
-    dims: Mapping[Any, int],
+    dims: Iterable[Any],
     explicit_coords: Iterable[Hashable],
 ) -> None:
     """Validate explicit coordinate names/dims.
@@ -721,16 +721,16 @@ def merge_core(
         collected, prioritized, compat=compat, combine_attrs=combine_attrs
     )
 
-    dims = calculate_dimensions(variables)
+    sizes = calculate_dimensions(variables)
 
     coord_names, noncoord_names = determine_coords(coerced)
     if compat == "minimal":
         # coordinates may be dropped in merged results
         coord_names.intersection_update(variables)
     if explicit_coords is not None:
-        assert_valid_explicit_coords(variables, dims, explicit_coords)
+        assert_valid_explicit_coords(variables, sizes.keys(), explicit_coords)
         coord_names.update(explicit_coords)
-    for dim, size in dims.items():
+    for dim, size in sizes.items():
         if dim in variables:
             coord_names.add(dim)
     ambiguous_coords = coord_names.intersection(noncoord_names)
@@ -745,7 +745,7 @@ def merge_core(
         combine_attrs,
     )
 
-    return _MergeResult(variables, coord_names, dims, out_indexes, attrs)
+    return _MergeResult(variables, coord_names, sizes, out_indexes, attrs)
 
 
 def merge(

xarray/tests/test_coordinates.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import numpy as np
 import pandas as pd
 import pytest
 
@@ -8,7 +9,7 @@
 from xarray.core.dataarray import DataArray
 from xarray.core.dataset import Dataset
 from xarray.core.indexes import PandasIndex, PandasMultiIndex
-from xarray.core.variable import IndexVariable
+from xarray.core.variable import IndexVariable, Variable
 from xarray.tests import assert_identical, source_ndarray
 
 
@@ -69,6 +70,12 @@ def test_init_dim_sizes_conflict(self) -> None:
         with pytest.raises(ValueError):
             Coordinates(coords={"foo": ("x", [1, 2]), "bar": ("x", [1, 2, 3, 4])})
 
+    def test_init_var_shares_name_with_dim(self) -> None:
+        # regression test for GH #8883
+        var = Variable(data=np.arange(6).reshape(2, 3), dims=["x", "y"])
+        with pytest.raises(ValueError):
+            Coordinates(coords={"x": var}, indexes={})
+
     def test_from_pandas_multiindex(self) -> None:
         midx = pd.MultiIndex.from_product([["a", "b"], [1, 2]], names=("one", "two"))
         coords = Coordinates.from_pandas_multiindex(midx, "x")