Added type checks to ansi.style()

cmd2/ansi.py

@@ -970,6 +970,8 @@ def style(
     :param overline: apply the overline style if True. Defaults to False.
     :param strikethrough: apply the strikethrough style if True. Defaults to False.
     :param underline: apply the underline style if True. Defaults to False.
+    :raises: TypeError if fg isn't None or a subclass of FgColor
+    :raises: TypeError if bg isn't None or a subclass of BgColor
     :return: the stylized string
     """
     # List of strings that add style
@@ -980,10 +982,14 @@ def style(
 
     # Process the style settings
     if fg is not None:
+        if not isinstance(fg, FgColor):
+            raise TypeError("fg must be a subclass of FgColor")
         additions.append(fg)
         removals.append(Fg.RESET)
 
     if bg is not None:
+        if not isinstance(bg, BgColor):
+            raise TypeError("bg must a subclass of BgColor")
         additions.append(bg)
         removals.append(Bg.RESET)
 

tests/test_ansi.py

@@ -58,6 +58,17 @@ def test_style_bg(bg_color):
     assert ansi.style(base_str, bg=bg_color) == ansi_str
 
 
+# noinspection PyTypeChecker
+def test_style_invalid_types():
+    # Use a BgColor with fg
+    with pytest.raises(TypeError):
+        ansi.style('test', fg=ansi.Bg.BLUE)
+
+    # Use a FgColor with bg
+    with pytest.raises(TypeError):
+        ansi.style('test', bg=ansi.Fg.BLUE)
+
+
 def test_style_bold():
     base_str = HELLO_WORLD
     ansi_str = ansi.TextStyle.INTENSITY_BOLD + base_str + ansi.TextStyle.INTENSITY_NORMAL
@@ -236,7 +247,6 @@ def test_sequence_str_building(ansi_sequence):
     ],
 )
 def test_rgb_bounds(r, g, b, valid):
-
     if valid:
         ansi.RgbFg(r, g, b)
         ansi.RgbBg(r, g, b)