initial changes

Author: AndrewILWilliams

xarray/core/computation.py

@@ -1327,7 +1327,23 @@ def _cov_corr(da_a, da_b, dim=None, ddof=0, method=None):
     # 2. Ignore the nans
     valid_values = da_a.notnull() & da_b.notnull()
 
-    if not valid_values.all():
+    def _nan_check(d):
+        if d.all():
+            return True
+        else:
+            return False
+
+    if is_duck_dask_array(valid_values.data):
+        # assign to copy - else the check is not triggered
+        _are_there_nans = valid_values.copy(
+            data=valid_values.data.map_blocks(_nan_check, dtype=valid_values.dtype),
+            deep=False,
+        )
+
+    else:
+        _are_there_nans = _nan_check(valid_values.data)
+
+    if not _are_there_nans:
         da_a = da_a.where(valid_values)
         da_b = da_b.where(valid_values)