List coordinates in concat error message, update test

pydata · Aug 19, 2023 · 26cb28e · 26cb28e
1 parent b7b2488
commit 26cb28e
Show file tree

Hide file tree

Showing 2 changed files with 12 additions and 6 deletions.
diff --git a/xarray/core/concat.py b/xarray/core/concat.py
@@ -391,17 +391,20 @@ def process_subset_opt(opt, subset):
             else:
                 raise ValueError(f"unexpected value for {subset}: {opt}")
         else:
-            invalid_vars = [k for k in opt if k not in getattr(datasets[0], subset)]
+            valid_vars = tuple(getattr(datasets[0], subset))
+            invalid_vars = [k for k in opt if k not in valid_vars]
             if invalid_vars:
                 if subset == "coords":
                     raise ValueError(
-                        "some variables in coords are not coordinates on "
-                        f"the first dataset: {invalid_vars}"
+                        f"the variables {invalid_vars} in coords are not "
+                        f"found in the coordinates of the first dataset {valid_vars}"
                     )
                 else:
+                    # note: data_vars are not listed in the error message here,
+                    # because there may be lots of them
                     raise ValueError(
-                        "some variables in data_vars are not data variables "
-                        f"on the first dataset: {invalid_vars}"
+                        f"the variables {invalid_vars} in data_vars are not "
+                        f"found in the data variables of the first dataset"
                     )
             concat_over.update(opt)
 

diff --git a/xarray/tests/test_concat.py b/xarray/tests/test_concat.py
@@ -614,9 +614,12 @@ def test_concat_errors(self):
         with pytest.raises(ValueError, match=r"must supply at least one"):
             concat([], "dim1")
 
-        with pytest.raises(ValueError, match=r"are not coordinates"):
+        with pytest.raises(ValueError, match=r"are not found in the coordinates"):
             concat([data, data], "new_dim", coords=["not_found"])
 
+        with pytest.raises(ValueError, match=r"are not found in the data variables"):
+            concat([data, data], "new_dim", data_vars=["not_found"])
+
         with pytest.raises(ValueError, match=r"global attributes not"):
             # call deepcopy seperately to get unique attrs
             data0 = deepcopy(split_data[0])