✨ Add automatic completion options by default, if click-completion is installed

typer/completion.py

@@ -0,0 +1,46 @@
+from typing import Any
+
+import click
+import click_completion
+import click_completion.core
+
+from .params import Option
+
+click_completion.init()
+
+
+def install_callback(ctx: click.Context, param: click.Parameter, value: Any) -> Any:
+    if not value or ctx.resilient_parsing:
+        return value
+    shell, path = click_completion.core.install()
+    click.echo(f"{shell} completion installed in {path}")
+    exit(0)
+
+
+def show_callback(ctx: click.Context, param: click.Parameter, value: Any) -> Any:
+    if not value or ctx.resilient_parsing:
+        return value
+    click.echo(click_completion.core.get_code())
+    exit(0)
+
+
+# Create a fake command function to extract the completion parameters
+def _install_completion_placeholder_function(
+    install_completion: bool = Option(
+        None,
+        "--install-completion",
+        is_flag=True,
+        callback=install_callback,
+        expose_value=False,
+        help="Install completion for the current shell.",
+    ),
+    show_completion: bool = Option(
+        None,
+        "--show-completion",
+        is_flag=True,
+        callback=show_callback,
+        expose_value=False,
+        help="Show completion for the current shell, to copy it or customize the installation.",
+    ),
+) -> Any:
+    pass

typer/main.py

@@ -25,6 +25,20 @@ from .models import (
     TyperInfo,
 )
 
+try:
+    import click_completion
+    from .completion import _install_completion_placeholder_function
+except ImportError:
+    click_completion = None
+
+
+def get_install_completion_arguments() -> Tuple[click.Parameter, click.Parameter]:
+    signature = inspect.signature(_install_completion_placeholder_function)
+    install_param, show_param = signature.parameters.values()
+    click_install_param, _ = get_click_param(install_param)
+    click_show_param, _ = get_click_param(show_param)
+    return click_install_param, click_show_param
+
 
 class Typer:
     def __init__(
@@ -47,7 +61,9 @@ class Typer:
         add_help_option: bool = Default(True),
         hidden: bool = Default(False),
         deprecated: bool = Default(False),
+        add_completion: bool = True,
     ):
+        self._add_completion = add_completion
         self.info = TyperInfo(
             name=name,
             cls=cls,
@@ -204,14 +220,27 @@ def get_group(typer_instance: Typer) -> click.Command:
 
 
 def get_command(typer_instance: Typer) -> click.Command:
+    if typer_instance._add_completion and click_completion:
+        click_completion.init()
+        click_install_param, click_show_param = get_install_completion_arguments()
     if (
         typer_instance.registered_callback
         or typer_instance.registered_groups
         or len(typer_instance.registered_commands) > 1
     ):
-        return get_group(typer_instance)
+        # Create a Group
+        click_command = get_group(typer_instance)
+        if typer_instance._add_completion and click_completion:
+            click_command.params.append(click_install_param)
+            click_command.params.append(click_show_param)
+        return click_command
     elif len(typer_instance.registered_commands) == 1:
-        return get_command_from_info(typer_instance.registered_commands[0])
+        # Create a single Command
+        click_command = get_command_from_info(typer_instance.registered_commands[0])
+        if typer_instance._add_completion and click_completion:
+            click_command.params.append(click_install_param)
+            click_command.params.append(click_show_param)
+        return click_command
     assert False, "Could not get a command for this Typer instance"
 
 
@@ -419,7 +448,7 @@ def get_click_type(
                 min_ = int(parameter_info.min)
             if parameter_info.max is not None:
                 max_ = int(parameter_info.max)
-            return click.IntRange(min=min_, max=max_, clamp=parameter_info.clamp,)
+            return click.IntRange(min=min_, max=max_, clamp=parameter_info.clamp)
         else:
             return click.INT
     elif annotation == float: