add help command

src/ahriman/application/ahriman.py

@@ -72,7 +72,8 @@ def _parser() -> argparse.ArgumentParser:
     subparsers = parser.add_subparsers(title="command", help="command to run", dest="command", required=True)
 
     _set_aur_search_parser(subparsers)
-    _set_help_commands_unsafe(subparsers)
+    _set_help_parser(subparsers)
+    _set_help_commands_unsafe_parser(subparsers)
     _set_key_import_parser(subparsers)
     _set_package_add_parser(subparsers)
     _set_package_remove_parser(subparsers)
@@ -119,7 +120,22 @@ def _set_aur_search_parser(root: SubParserAction) -> argparse.ArgumentParser:
     return parser
 
 
-def _set_help_commands_unsafe(root: SubParserAction) -> argparse.ArgumentParser:
+def _set_help_parser(root: SubParserAction) -> argparse.ArgumentParser:
+    """
+    add parser for listing help subcommand
+    :param root: subparsers for the commands
+    :return: created argument parser
+    """
+    parser = root.add_parser("help", help="show help message",
+                             description="show help message for application or command and exit",
+                             formatter_class=_formatter)
+    parser.add_argument("command", help="show help message for specific command", nargs="?")
+    parser.set_defaults(handler=handlers.Help, architecture=[""], lock=None, no_report=True, quiet=True,
+                        unsafe=True, parser=_parser)
+    return parser
+
+
+def _set_help_commands_unsafe_parser(root: SubParserAction) -> argparse.ArgumentParser:
     """
     add parser for listing unsafe commands
     :param root: subparsers for the commands

src/ahriman/application/handlers/__init__.py

@@ -22,6 +22,7 @@ from ahriman.application.handlers.handler import Handler
 from ahriman.application.handlers.add import Add
 from ahriman.application.handlers.clean import Clean
 from ahriman.application.handlers.dump import Dump
+from ahriman.application.handlers.help import Help
 from ahriman.application.handlers.key_import import KeyImport
 from ahriman.application.handlers.patch import Patch
 from ahriman.application.handlers.rebuild import Rebuild

src/ahriman/application/handlers/help.py

@@ -0,0 +1,50 @@
+#
+# Copyright (c) 2021-2022 ahriman team.
+#
+# This file is part of ahriman
+# (see https://github.com/arcan1s/ahriman).
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+import argparse
+
+from typing import Type
+
+from ahriman.application.handlers.handler import Handler
+from ahriman.core.configuration import Configuration
+
+
+class Help(Handler):
+    """
+    help handler
+    """
+
+    ALLOW_AUTO_ARCHITECTURE_RUN = False  # it should be called only as "no-architecture"
+
+    @classmethod
+    def run(cls: Type[Handler], args: argparse.Namespace, architecture: str,
+            configuration: Configuration, no_report: bool, unsafe: bool) -> None:
+        """
+        callback for command line
+        :param args: command line args
+        :param architecture: repository architecture
+        :param configuration: configuration instance
+        :param no_report: force disable reporting
+        :param unsafe: if set no user check will be performed before path creation
+        """
+        parser: argparse.ArgumentParser = args.parser()
+        if args.command is None:
+            parser.parse_args(["--help"])
+        else:
+            parser.parse_args([args.command, "--help"])

tests/ahriman/application/handlers/test_handler_help.py

@@ -0,0 +1,41 @@
+import argparse
+
+from pytest_mock import MockerFixture
+
+from ahriman.application.ahriman import _parser
+from ahriman.application.handlers import Help
+from ahriman.core.configuration import Configuration
+
+
+def _default_args(args: argparse.Namespace) -> argparse.Namespace:
+    """
+    default arguments for these test cases
+    :param args: command line arguments fixture
+    :return: generated arguments for these test cases
+    """
+    args.parser = _parser
+    args.command = None
+    return args
+
+
+def test_run(args: argparse.Namespace, configuration: Configuration, mocker: MockerFixture) -> None:
+    """
+    must run command
+    """
+    args = _default_args(args)
+    parse_mock = mocker.patch("argparse.ArgumentParser.parse_args")
+
+    Help.run(args, "x86_64", configuration, True, False)
+    parse_mock.assert_called_once_with(["--help"])
+
+
+def test_run_command(args: argparse.Namespace, configuration: Configuration, mocker: MockerFixture) -> None:
+    """
+    must run command for specific subcommand
+    """
+    args = _default_args(args)
+    args.command = "aur-search"
+    parse_mock = mocker.patch("argparse.ArgumentParser.parse_args")
+
+    Help.run(args, "x86_64", configuration, True, False)
+    parse_mock.assert_called_once_with(["aur-search", "--help"])

tests/ahriman/application/test_ahriman.py

@@ -65,6 +65,27 @@ def test_subparsers_aur_search_architecture(parser: argparse.ArgumentParser) ->
     assert args.architecture == [""]
 
 
+def test_subparsers_help(parser: argparse.ArgumentParser) -> None:
+    """
+    help command must imply architecture list, lock, no-report, quiet, unsafe and parser
+    """
+    args = parser.parse_args(["help"])
+    assert args.architecture == [""]
+    assert args.lock is None
+    assert args.no_report
+    assert args.quiet
+    assert args.unsafe
+    assert args.parser is not None and args.parser()
+
+
+def test_subparsers_help_architecture(parser: argparse.ArgumentParser) -> None:
+    """
+    help command must correctly parse architecture list
+    """
+    args = parser.parse_args(["-a", "x86_64", "help"])
+    assert args.architecture == [""]
+
+
 def test_subparsers_help_commands_unsafe(parser: argparse.ArgumentParser) -> None:
     """
     help-commands-unsafe command must imply architecture list, lock, no-report, quiet, unsafe and parser
@@ -80,7 +101,7 @@ def test_subparsers_help_commands_unsafe(parser: argparse.ArgumentParser) -> Non
 
 def test_subparsers_help_commands_unsafe_architecture(parser: argparse.ArgumentParser) -> None:
     """
-    help-ommands-unsafe command must correctly parse architecture list
+    help-commands-unsafe command must correctly parse architecture list
     """
     args = parser.parse_args(["-a", "x86_64", "help-commands-unsafe"])
     assert args.architecture == [""]