Lexer colors now change if a user changes the theme during runtime

Since prommpt-toolkit calls the lex_document method of the Cmd2Lexer instance quite frequnetly, we don't want to dynamically fetech the colors to use on every call.

Instead I extracted the code for retrieving the lexer colors from the rich theme into a set_colors helper method and the set_theme method will call this for any Cmd2Lexer instances.

Author: tleonhardt

cmd2/pt_utils.py

@@ -1,6 +1,7 @@
 """Utilities for integrating prompt_toolkit with cmd2."""
 
 import re
+import weakref
 from collections.abc import (
     Callable,
     Iterable,
@@ -254,6 +255,9 @@ def clear(self) -> None:
         self._loaded_strings.clear()
 
 
+_lexers: "weakref.WeakSet[Cmd2Lexer]" = weakref.WeakSet()
+
+
 class Cmd2Lexer(Lexer):
     """Lexer that highlights cmd2 command names, aliases, and macros."""
 
@@ -268,6 +272,11 @@ def __init__(
         super().__init__()
         self.cmd_app = cmd_app
 
+        _lexers.add(self)
+        self.set_colors()
+
+    def set_colors(self) -> None:
+        """Update colors from the current rich theme."""
         # Retrieve styles dynamically from the current theme
         theme = ru.get_theme()
         self.command_color = rich_to_pt_style(theme.styles.get(Cmd2Style.LEXER_COMMAND, ""))

cmd2/rich_utils.py

@@ -351,6 +351,15 @@ def set_theme(styles: Mapping[str, StyleType] | None = None) -> None:
     for name in Cmd2HelpFormatter.styles.keys() & theme.styles.keys():
         Cmd2HelpFormatter.styles[name] = theme.styles[name]
 
+    # Update colors in active prompt-toolkit lexers
+    try:
+        from . import pt_utils
+
+        for lexer in pt_utils._lexers:
+            lexer.set_colors()
+    except ImportError:
+        pass
+
 
 def _create_default_theme() -> Theme:
     """Create a default theme for the application.

tests/test_pt_utils.py

@@ -278,6 +278,31 @@ def test_lex_document_multiline(self, mock_cmd_app):
         tokens1 = get_line(1)
         assert tokens1 == [("noreverse fg:ansiyellow bg:default", "help")]
 
+    def test_lexer_set_theme_runtime_update(self, mock_cmd_app):
+        """Test that changing the theme updates active lexers."""
+        lexer = pt_utils.Cmd2Lexer(cast(Any, mock_cmd_app))
+
+        # Get the old color for command
+        old_color = lexer.command_color
+
+        # Change the theme dynamically
+        from rich.style import Style
+
+        from cmd2.styles import Cmd2Style
+
+        new_styles = {Cmd2Style.LEXER_COMMAND: Style(color="red", bgcolor="black")}
+
+        try:
+            ru.set_theme(new_styles)
+
+            # Now verify the lexer's color was updated
+            assert lexer.command_color != old_color
+            assert "ansired" in lexer.command_color
+            assert "ansiblack" in lexer.command_color
+
+        finally:
+            ru.set_theme()  # Reset to default
+
 
 class TestCmd2Completer:
     def test_get_completions(self, mock_cmd_app: MockCmd, monkeypatch) -> None: