dataset fix and more tests

xarray/core/dataset.py

@@ -3278,11 +3278,11 @@ def rank(self, dim, pct=False, keep_attrs=False):
 
         variables = OrderedDict()
         for name, var in iteritems(self.variables):
-            if name in self.data_vars and dim in var.dims:
-                variables[name] = var.rank(dim, pct=pct)
-                variables.update({
-                    k: self.variables[k] for k in var.dims
-                    if k not in variables and k in self.variables})
+            if name in self.data_vars:
+                if dim in var.dims:
+                    variables[name] = var.rank(dim, pct=pct)
+            else:
+                variables[name] = var
 
         coord_names = set(k for k in self.coords if k in variables)
         attrs = self.attrs if keep_attrs else None

xarray/tests/test_dataset.py

@@ -3417,9 +3417,19 @@ def test_quantile(self):
     @requires_bottleneck
     def test_rank(self):
         ds = create_test_data(seed=1234)
-        x = ds.rank('dim3').var3
+        # only ds.var3 depends on dim3
+        z = ds.rank('dim3')
+        self.assertItemsEqual(['var3'], list(z.data_vars))
+        # same as dataarray version
+        x = z.var3
         y = ds.var3.rank('dim3')
         self.assertDataArrayEqual(x, y)
+        # coordinates stick
+        self.assertItemsEqual(list(z.coords), list(ds.coords))
+        self.assertItemsEqual(list(x.coords), list(y.coords))
+        # invalid dim
+        with raises_regex(ValueError, 'does not contain'):
+            x.rank('invalid_dim')
 
     def test_count(self):
         ds = Dataset({'x': ('a', [np.nan, 1]), 'y': 0, 'z': np.nan})

xarray/tests/test_variable.py

@@ -1355,6 +1355,13 @@ def test_quantile_dask_raises(self):
         with raises_regex(TypeError, 'arrays stored as dask'):
             v.quantile(0.5, dim='x')
 
+    @requires_dask
+    @requires_bottleneck
+    def test_rank_dask_raises(self):
+        v = Variable(['x'], [3.0, 1.0, np.nan, 2.0, 4.0]).chunk(2)
+        with raises_regex(TypeError, 'arrays stored as dask'):
+            v.rank('x')
+
     @requires_bottleneck
     def test_rank(self):
         import bottleneck as bn
@@ -1376,6 +1383,9 @@ def test_rank(self):
         v = Variable(['x'], [3.0, 1.0, np.nan, 2.0, 4.0])
         v_expect = Variable(['x'], [0.75, 0.25, np.nan, 0.5, 1.0])
         self.assertVariableEqual(v.rank('x', pct=True), v_expect)
+        # invalid dim
+        with raises_regex(ValueError, 'not found'):
+            v.rank('y')
 
     def test_big_endian_reduce(self):
         # regression test for GH489