TST: Add tests for new pd.eval behavior

Author: gfyoung

pandas/tests/computation/test_eval.py

@@ -58,6 +58,11 @@ def engine_has_neg_frac(engine):
     return _engines[engine].has_neg_frac
 
 
+@pytest.fixture(params=[1, "cat", [1, 2], np.array([]), (1, 3)])
+def invalid_target(request):
+    return request.param
+
+
 def _eval_single_bin(lhs, cmp1, rhs, engine):
     c = _binary_ops_dict[cmp1]
     if engine_has_neg_frac(engine):
@@ -1388,6 +1393,34 @@ def query_inplace(self):
         df.query('a == 2', inplace=True)
         assert_frame_equal(expected, df)
 
+        df = {}
+        expected = {"a": 3}
+
+        self.eval("a = 1 + 2", target=df, inplace=True)
+        tm.assert_dict_equal(df, expected)
+
+    def cannot_item_assign(self, invalid_target):
+        msg = "Cannot assign expression output to target"
+        expr = "a = 1 + 2"
+
+        with tm.assert_raises_regex(ValueError, msg):
+            self.eval(expr, target=invalid_target, inplace=True)
+
+    def cannot_copy_item(self, invalid_target):
+        msg = "Cannot return a copy of the target"
+        expr = "a = 1 + 2"
+
+        with tm.assert_raises_regex(ValueError, msg):
+            self.eval(expr, target=invalid_target, inplace=False)
+
+    def ignore_invalid_target_no_assignment(self, invalid_target):
+        # No Exception should be raised because we are
+        # not performing item assignment in this test.
+        expr = "1 + 2"
+
+        assert self.eval(expr, target=invalid_target, inplace=False) == 3
+        assert self.eval(expr, target=invalid_target, inplace=True) is None
+
     def test_basic_period_index_boolean_expression(self):
         df = mkdf(2, 2, data_gen_f=f, c_idx_type='p', r_idx_type='i')