Don't replace local coords variable inside iterator

Closes #5046

Author: michaelosthege

pymc/backends/arviz.py

@@ -131,9 +131,9 @@ def dict_to_dataset(
         for name, vals in data.items():
             vals = np.atleast_1d(vals)
             val_dims = dims.get(name)
-            val_dims, coords = generate_dims_coords(vals.shape, name, dims=val_dims, coords=coords)
-            coords = {key: xr.IndexVariable((key,), data=coords[key]) for key in val_dims}
-            out_data[name] = xr.DataArray(vals, dims=val_dims, coords=coords)
+            val_dims, crds = generate_dims_coords(vals.shape, name, dims=val_dims, coords=coords)
+            crds = {key: xr.IndexVariable((key,), data=crds[key]) for key in val_dims}
+            out_data[name] = xr.DataArray(vals, dims=val_dims, coords=crds)
         return xr.Dataset(data_vars=out_data, attrs=make_attrs(attrs=attrs, library=library))
 
 

pymc/tests/test_idata_conversion.py

@@ -568,9 +568,8 @@ def test_multivariate_observations(self):
         assert "direction" not in idata.log_likelihood.dims
         assert "direction" in idata.observed_data.dims
 
-    @pytest.mark.xfail(reason="Critical bug in dataset conversion.")
     def test_constant_data_coords_issue_5046(self):
-        # For some reason only the first entry of the `dims` ends up in the dataset.
+        """This is a regression test against a bug where a local coords variable was overwritten."""
         dims = {
             "alpha": ["backwards"],
             "bravo": ["letters", "yesno"],