add docs and test for 'no_args_is_help'

docs/tutorial/commands/index.md

@@ -211,6 +211,38 @@ Notice that the help text now shows the 2 commands: `create` and `delete`.
 !!! tip
     By default, the names of the commands are generated from the function name.
 
+## Show the help message if no command is given
+
+By default, we need to specify `--help` to get the command's help page. 
+
+However, by setting `no_args_is_help=True` when defining the `typer.Typer()` application, the help function will be shown whenever no argument is given:
+
+```Python hl_lines="3"
+{!../docs_src/commands/index/tutorial003.py!}
+```
+
+Now we can run this:
+
+<div class="termy">
+
+```console
+// Check the help without having to type --help
+$ python main.py
+
+Usage: main.py [OPTIONS] COMMAND [ARGS]...
+
+Options:
+  --install-completion  Install completion for the current shell.
+  --show-completion     Show completion for the current shell, to copy it or customize the installation.
+  --help                Show this message and exit.
+
+Commands:
+  create
+  delete
+```
+
+</div>
+
 ## Click Group
 
 If you come from Click, a `typer.Typer` app with subcommands is more or less the equivalent of a <a href="https://click.palletsprojects.com/en/7.x/quickstart/#nesting-commands" class="external-link" target="_blank">Click Group</a>.

docs_src/commands/index/tutorial003.py

@@ -0,0 +1,17 @@
+import typer
+
+app = typer.Typer(no_args_is_help=True)
+
+
+@app.command()
+def create():
+    print("Creating user: Hiro Hamada")
+
+
+@app.command()
+def delete():
+    print("Deleting user: Hiro Hamada")
+
+
+if __name__ == "__main__":
+    app()

tests/test_tutorial/test_commands/test_index/test_tutorial003.py

@@ -0,0 +1,29 @@
+import subprocess
+import sys
+
+from typer.testing import CliRunner
+
+from docs_src.commands.index import tutorial003 as mod
+
+app = mod.app
+
+runner = CliRunner()
+
+
+def test_no_arg():
+    result = runner.invoke(app)
+    assert result.exit_code == 0
+    assert "[OPTIONS] COMMAND [ARGS]..." in result.output
+    assert "Commands" in result.output
+    assert "create" in result.output
+    assert "delete" in result.output
+
+
+def test_script():
+    result = subprocess.run(
+        [sys.executable, "-m", "coverage", "run", mod.__file__, "--help"],
+        stdout=subprocess.PIPE,
+        stderr=subprocess.PIPE,
+        encoding="utf-8",
+    )
+    assert "Usage" in result.stdout