Fix: trigger result_callback for single command apps (Issue #445)

tests/test_single_command_callback.py

@@ -0,0 +1,59 @@
+import typer
+from typer.testing import CliRunner
+
+runner: CliRunner = CliRunner()
+
+
+def test_result_callback_single_command() -> None:
+    # A list to capture the result from the callback
+    captured_results: list[str] = []
+
+    def my_callback(value: str) -> None:
+        captured_results.append(value)
+
+    # Create app with a result_callback
+    app: typer.Typer = typer.Typer(result_callback=my_callback)
+
+    @app.command()
+    def main() -> str:
+        return "single_command_result"
+
+    # Invoke the app (using the single command fast-path)
+    result = runner.invoke(app, [])
+
+    # Verify the command ran successfully
+    assert result.exit_code == 0
+
+    # CRITICAL: Verify the callback was actually executed
+    assert "single_command_result" in captured_results, (
+        "Result callback was not triggered for single command!"
+    )
+
+
+def test_result_callback_single_command_placeholder() -> None:
+    from typer.models import DefaultPlaceholder
+
+    # A list to capture the result from the callback
+    captured_results: list[str] = []
+
+    def my_callback(value: str) -> None:
+        captured_results.append(value)
+
+    # Create app and manually inject a DefaultPlaceholder for the result_callback
+    app = typer.Typer()
+    app.info.result_callback = DefaultPlaceholder(my_callback)
+
+    @app.command()
+    def main() -> str:
+        return "placeholder_result"
+
+    # Invoke the app
+    result = runner.invoke(app, [])
+
+    # Verify the command ran successfully
+    assert result.exit_code == 0
+
+    # Verify the callback was actually executed via the placeholder path
+    assert "placeholder_result" in captured_results, (
+        "Result callback was not triggered via placeholder!"
+    )

typer/main.py

@@ -1200,6 +1200,25 @@ def get_command(typer_instance: Typer) -> click.Command:
         if typer_instance._add_completion:
             click_command.params.append(click_install_param)
             click_command.params.append(click_show_param)
+
+        click_callback = click_command.callback
+        use_result_callback = None
+        if typer_instance.info.result_callback:
+            if isinstance(typer_instance.info.result_callback, DefaultPlaceholder):
+                use_result_callback = typer_instance.info.result_callback.value
+            else:
+                use_result_callback = typer_instance.info.result_callback
+
+        if click_callback and use_result_callback:
+
+            def callback_wrapper(*args: Any, **kwargs: Any) -> Any:
+                result = click_callback(*args, **kwargs)
+                ctx = click.get_current_context()
+                return ctx.invoke(use_result_callback, result)
+
+            update_wrapper(callback_wrapper, click_callback)
+            click_command.callback = callback_wrapper
+
         return click_command
     raise RuntimeError(
         "Could not get a command for this Typer instance"