Updated stylize() unit test.

Author: kmvanbrunt

cmd2/string_utils.py

@@ -82,22 +82,23 @@ def align_right(
 
 
 def stylize(val: str, style: StyleType) -> str:
-    """Apply ANSI style to a string.
+    """Apply an ANSI style to a string, preserving any existing styles.
 
     :param val: string to be styled
     :param style: style instance or style definition to apply.
     :return: the stylized string
     """
+    # Convert to a Rich Text object to parse and preserve existing ANSI styles.
     text = ru.string_to_rich_text(val)
     text.stylize(style)
     return ru.rich_text_to_string(text)
 
 
 def strip_style(val: str) -> str:
-    """Strip ANSI style sequences from a string.
+    """Strip all ANSI styles from a string.
 
-    :param val: string which may contain ANSI style sequences
-    :return: the same string with any ANSI style sequences removed
+    :param val: string to be stripped
+    :return: the stripped string
     """
     text = ru.string_to_rich_text(val)
     return text.plain

tests/test_string_utils.py

@@ -115,18 +115,16 @@ def test_align_right_with_style() -> None:
 
 
 def test_stylize() -> None:
-    styled_str = su.stylize(
-        HELLO_WORLD,
-        style=Style(
-            color=Color.GREEN,
-            bgcolor=Color.BLUE,
-            bold=True,
-            underline=True,
-        ),
-    )
-
+    # Test string with no existing style
+    style = Style(color=Color.GREEN, bgcolor=Color.BLUE, bold=True, underline=True)
+    styled_str = su.stylize(HELLO_WORLD, style=style)
     assert styled_str == "\x1b[1;4;32;44mHello, world!\x1b[0m"
 
+    # Add style to already-styled string
+    updated_style = Style.combine([style, Style(strike=True)])
+    restyled_string = su.stylize(styled_str, style=updated_style)
+    assert restyled_string == "\x1b[1;4;9;32;44mHello, world!\x1b[0m"
+
 
 def test_strip_style() -> None:
     base_str = HELLO_WORLD