Make the naked invocation display a compacted help

httpie/cli/argparser.py

@@ -47,12 +47,39 @@ def _split_lines(self, text, width):
         text = dedent(text).strip() + '\n\n'
         return text.splitlines()
 
+    def add_usage(self, usage, actions, groups, prefix=None):
+        # Only display the positional arguments
+        displayed_actions = [
+            action
+            for action in actions
+            if not action.option_strings
+        ]
+
+        _, exception, _ = sys.exc_info()
+        if (
+            isinstance(exception, argparse.ArgumentError)
+            and len(exception.args) >= 1
+            and isinstance(exception.args[0], argparse.Action)
+        ):
+            # add_usage path is also taken when you pass an invalid option,
+            # e.g --style=invalid. If something like that happens, we want
+            # to include to action that caused to the invalid usage into
+            # the list of actions we are displaying.
+            displayed_actions.insert(0, exception.args[0])
+
+        super().add_usage(
+            usage,
+            displayed_actions,
+            groups,
+            prefix="usage:\n    "
+        )
+
 
 # TODO: refactor and design type-annotated data structures
 #       for raw args + parsed args and keep things immutable.
 class BaseHTTPieArgumentParser(argparse.ArgumentParser):
-    def __init__(self, *args, formatter_class=HTTPieHelpFormatter, **kwargs):
-        super().__init__(*args, formatter_class=formatter_class, **kwargs)
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
         self.env = None
         self.args = None
         self.has_stdin_data = False
@@ -115,9 +142,9 @@ class HTTPieArgumentParser(BaseHTTPieArgumentParser):
 
     """
 
-    def __init__(self, *args, **kwargs):
+    def __init__(self, *args, formatter_class=HTTPieHelpFormatter, **kwargs):
         kwargs.setdefault('add_help', False)
-        super().__init__(*args, **kwargs)
+        super().__init__(*args, formatter_class=formatter_class, **kwargs)
 
     # noinspection PyMethodOverriding
     def parse_args(
@@ -512,3 +539,15 @@ def _process_format_options(self):
         for options_group in format_options:
             parsed_options = parse_format_options(options_group, defaults=parsed_options)
         self.args.format_options = parsed_options
+
+    def error(self, message):
+        """Prints a usage message incorporating the message to stderr and
+        exits."""
+        self.print_usage(sys.stderr)
+        args = {'prog': self.prog, 'message': message}
+        self.exit(
+            2,
+            '\nerror:\n    %(message)s\n\n'
+            'For more information try with --help '
+            'or visit the https://pie.co/docs' % args
+        )

tests/test_cli_ui.py

@@ -0,0 +1,65 @@
+import pytest
+import shutil
+import os
+from tests.utils import http
+
+NAKED_HELP_MESSAGE = """\
+usage:
+    http [METHOD] URL [REQUEST_ITEM ...]
+
+error:
+    the following arguments are required: URL
+
+For more information try with --help or visit the https://pie.co/docs
+"""
+
+NAKED_HELP_MESSAGE_PRETTY_WITH_NO_ARG = """\
+usage:
+    http [--pretty {all,colors,format,none}] [METHOD] URL [REQUEST_ITEM ...]
+
+error:
+    argument --pretty: expected one argument
+
+For more information try with --help or visit the https://pie.co/docs
+"""
+
+NAKED_HELP_MESSAGE_PRETTY_WITH_INVALID_ARG = """\
+usage:
+    http [--pretty {all,colors,format,none}] [METHOD] URL [REQUEST_ITEM ...]
+
+error:
+    argument --pretty: invalid choice: '$invalid' (choose from 'all', 'colors', 'format', 'none')
+
+For more information try with --help or visit the https://pie.co/docs
+"""
+
+
+PREDEFINED_TERMINAL_SIZE = (160, 80)
+
+
+@pytest.fixture(scope="function")
+def ignore_terminal_size(monkeypatch):
+    """Some tests wrap/crop the output depending on the
+    size of the executed terminal, which might not be consistent
+    through all runs.
+
+    This fixture ensures every run uses the same exact configuration.
+    """
+
+    def fake_terminal_size(*args, **kwargs):
+        return os.terminal_size(PREDEFINED_TERMINAL_SIZE)
+
+    monkeypatch.setattr(shutil, "get_terminal_size", fake_terminal_size)
+
+
+@pytest.mark.parametrize(
+    "args, expected_msg", [
+        ([], NAKED_HELP_MESSAGE),
+        (["--pretty"], NAKED_HELP_MESSAGE_PRETTY_WITH_NO_ARG),
+        (["pie.dev", "--pretty"], NAKED_HELP_MESSAGE_PRETTY_WITH_NO_ARG),
+        (["--pretty", "$invalid"], NAKED_HELP_MESSAGE_PRETTY_WITH_INVALID_ARG),
+    ]
+)
+def test_naked_invocation(ignore_terminal_size, args, expected_msg):
+    result = http(*args, tolerate_error_exit_status=True)
+    assert result.stderr == expected_msg