Raised value error on incorrect na_option (#22037)

* added value error on incorrect na_option

* added test cases

Author: raguiar2

pandas/core/generic.py

@@ -7513,6 +7513,10 @@ def rank(self, axis=0, method='average', numeric_only=None,
             msg = "rank does not make sense when ndim > 2"
             raise NotImplementedError(msg)
 
+        if na_option not in {'keep', 'top', 'bottom'}:
+            msg = "na_option must be one of 'keep', 'top', or 'bottom'"
+            raise ValueError(msg)
+
         def ranker(data):
             ranks = algos.rank(data.values, axis=axis, method=method,
                                ascending=ascending, na_option=na_option,

pandas/tests/frame/test_rank.py

@@ -191,6 +191,16 @@ def test_rank_na_option(self):
         tm.assert_numpy_array_equal(ranks0.values, exp0)
         tm.assert_numpy_array_equal(ranks1.values, exp1)
 
+        # bad values throw error
+        msg = "na_option must be one of 'keep', 'top', or 'bottom'"
+
+        with tm.assert_raises_regex(ValueError, msg):
+            self.frame.rank(na_option='bad', ascending=False)
+
+        # invalid type
+        with tm.assert_raises_regex(ValueError, msg):
+            self.frame.rank(na_option=True, ascending=False)
+
     def test_rank_axis(self):
         # check if using axes' names gives the same result
         df = DataFrame([[2, 1], [4, 3]])

pandas/tests/groupby/test_rank.py

@@ -248,6 +248,17 @@ def test_rank_avg_even_vals():
 def test_rank_object_raises(ties_method, ascending, na_option,
                             pct, vals):
     df = DataFrame({'key': ['foo'] * 5, 'val': vals})
+
+    with tm.assert_raises_regex(TypeError, "not callable"):
+        df.groupby('key').rank(method=ties_method,
+                               ascending=ascending,
+                               na_option='bad', pct=pct)
+
+    with tm.assert_raises_regex(TypeError, "not callable"):
+        df.groupby('key').rank(method=ties_method,
+                               ascending=ascending,
+                               na_option=True, pct=pct)
+
     with tm.assert_raises_regex(TypeError, "not callable"):
         df.groupby('key').rank(method=ties_method,
                                ascending=ascending,

pandas/tests/series/test_rank.py

@@ -183,6 +183,16 @@ def test_rank_categorical(self):
             exp_keep
         )
 
+        # Test invalid values for na_option
+        msg = "na_option must be one of 'keep', 'top', or 'bottom'"
+
+        with tm.assert_raises_regex(ValueError, msg):
+            na_ser.rank(na_option='bad', ascending=False)
+
+        # invalid type
+        with tm.assert_raises_regex(ValueError, msg):
+            na_ser.rank(na_option=True, ascending=False)
+
         # Test with pct=True
         na_ser = Series(['first', 'second', 'third', 'fourth', np.NaN]).astype(
             CategoricalDtype(['first', 'second', 'third', 'fourth'], True))