Fix rendering of control whitespace in completion items

cmd2/completion.py

@@ -51,6 +51,8 @@
 class CompletionItem:
     """A single completion result."""
 
+    _SANITIZE_RE = re.compile(r'\r\n|[\n\r\t\f\v]')
+
     # The underlying object this completion represents (e.g., str, int, Path).
     # This is used to support argparse choices validation.
     value: Any = field(kw_only=False)
@@ -76,6 +78,15 @@ class CompletionItem:
     display_plain: str = field(init=False)
     display_meta_plain: str = field(init=False)
 
+    @classmethod
+    def _sanitize_display_string(cls, val: str) -> str:
+        """Sanitize a string for display in the completion menu.
+
+        This replaces whitespace characters that are rendered as
+        control sequences (like ^J or ^I) with spaces.
+        """
+        return cls._SANITIZE_RE.sub(' ', val)
+
     def __post_init__(self) -> None:
         """Finalize the object after initialization."""
         # Derive text from value if it wasn't explicitly provided
@@ -86,7 +97,11 @@ def __post_init__(self) -> None:
         if not self.display:
             object.__setattr__(self, "display", self.text)
 
-        # Pre-calculate plain text versions by stripping ANSI sequences.
+        # Sanitize display and display_meta
+        object.__setattr__(self, "display", self._sanitize_display_string(self.display))
+        object.__setattr__(self, "display_meta", self._sanitize_display_string(self.display_meta))
+
+        # Create plain text versions by stripping ANSI sequences.
         # These are stored as attributes for fast access during sorting/filtering.
         object.__setattr__(self, "display_plain", su.strip_style(self.display))
         object.__setattr__(self, "display_meta_plain", su.strip_style(self.display_meta))

tests/test_completion.py

@@ -932,6 +932,25 @@ def test_plain_fields() -> None:
     assert completion_item.display_meta_plain == "A tasty apple"
 
 
+def test_sanitization() -> None:
+    """Test display string sanitization in CompletionItem."""
+    # Test all problematic characters being replaced by a single space.
+    # Also verify that \r\n is replaced by a single space.
+    display = "str1\r\nstr2\nstr3\rstr4\tstr5\fstr6\vstr7"
+    expected = "str1 str2 str3 str4 str5 str6 str7"
+
+    # Since display defaults to text if not provided, we test both text and display fields
+    completion_item = CompletionItem("item", display=display, display_meta=display)
+    assert completion_item.display == expected
+    assert completion_item.display_meta == expected
+
+    # Verify that text derived display is also sanitized
+    text = "item\nwith\nnewlines"
+    expected_text_display = "item with newlines"
+    completion_item = CompletionItem(text)
+    assert completion_item.display == expected_text_display
+
+
 def test_styled_completion_sort() -> None:
     """Test that sorting is done with the display_plain field."""