🐛 Fix Rich formatting with no commands (#796)

tests/test_rich_utils.py

@@ -36,3 +36,17 @@ def secondary():
     assert "Hello World" in result.stdout
     result = runner.invoke(app, ["secondary"])
     assert "Hello Secondary World" in result.stdout
+
+
+def test_rich_help_no_commands():
+    """Ensure that the help still works for a Typer instance with no commands, but with a callback."""
+    app = typer.Typer(help="My cool Typer app")
+
+    @app.callback(invoke_without_command=True, no_args_is_help=True)
+    def main() -> None:
+        return None  # pragma: no cover
+
+    result = runner.invoke(app, ["--help"])
+
+    assert result.exit_code == 0
+    assert "Show this message" in result.stdout

typer/rich_utils.py

@@ -644,7 +644,8 @@ def rich_format_help(
                 len(command.name or "")
                 for commands in panel_to_commands.values()
                 for command in commands
-            ]
+            ],
+            default=0,
         )
 
         # Print each command group panel