Refactor subcommands

flit/__init__.py

@@ -5,23 +5,13 @@
 import sys
 
 from . import common
+from .subcommand import register
 from .log import enable_colourful_output
 
 __version__ = '1.3'
 
 log = logging.getLogger(__name__)
 
-def add_shared_install_options(parser):
-    parser.add_argument('--user', action='store_true', default=None,
-        help="Do a user-local install (default if site.ENABLE_USER_SITE is True)"
-    )
-    parser.add_argument('--env', action='store_false', dest='user',
-        help="Install into sys.prefix (default if site.ENABLE_USER_SITE is False, i.e. in virtualenvs)"
-    )
-    parser.add_argument('--python', default=sys.executable,
-        help="Target Python executable, if different from the one running flit"
-    )
-
 def main(argv=None):
     ap = argparse.ArgumentParser()
     ap.add_argument('-f', '--ini-file', type=pathlib.Path, default='pyproject.toml')
@@ -31,53 +21,13 @@ def main(argv=None):
     )
     ap.add_argument('--debug', action='store_true', help=argparse.SUPPRESS)
     ap.add_argument('--logo', action='store_true', help=argparse.SUPPRESS)
-    subparsers = ap.add_subparsers(title='subcommands', dest='subcmd')
-
-    parser_build = subparsers.add_parser('build',
-        help="Build wheel and sdist",
-    )
-
-    parser_build.add_argument('--format', action='append',
-        help="Select a format to build. Options: 'wheel', 'sdist'"
-    )
-
-    parser_publish = subparsers.add_parser('publish',
-        help="Upload wheel and sdist",
-    )
-
-    parser_publish.add_argument('--format', action='append',
-        help="Select a format to publish. Options: 'wheel', 'sdist'"
-    )
 
-    parser_install = subparsers.add_parser('install',
-        help="Install the package",
-    )
-    parser_install.add_argument('-s', '--symlink', action='store_true',
-        help="Symlink the module/package into site packages instead of copying it"
-    )
-    parser_install.add_argument('--pth-file', action='store_true',
-        help="Add .pth file for the module/package to site packages instead of copying it"
-    )
-    add_shared_install_options(parser_install)
-    parser_install.add_argument('--deps', choices=['all', 'production', 'develop', 'none'], default='all',
-        help="Which set of dependencies to install. If --deps=develop, the extras dev, doc, and test are installed"
-    )
-    parser_install.add_argument('--extras', default=(), type=lambda l: l.split(',') if l else (),
-        help="Install the dependencies of these (comma separated) extras additionally to the ones implied by --deps. "
-             "--extras=all can be useful in combination with --deps=production, --deps=none precludes using --extras"
-    )
-
-    parser_installfrom = subparsers.add_parser('installfrom',
-       help="Download and install a package using flit from source"
-    )
-    parser_installfrom.add_argument('location',
-        help="A URL to download, or a shorthand like github:takluyver/flit"
-    )
-    add_shared_install_options(parser_installfrom)
-
-    parser_init = subparsers.add_parser('init',
-        help="Prepare pyproject.toml for a new package"
-    )
+    subparsers = ap.add_subparsers(title='subcommands', dest='subcmd')
+    register(subparsers, 'build')
+    register(subparsers, 'publish')
+    register(subparsers, 'install')
+    register(subparsers, 'installfrom')
+    register(subparsers, 'info')
 
     args = ap.parse_args(argv)
 
@@ -104,30 +54,9 @@ def main(argv=None):
         print(clogo.format(version=__version__))
         sys.exit(0)
 
-    if args.subcmd == 'build':
-        from .build import main
-        try:
-            main(args.ini_file, formats=set(args.format or []))
-        except(common.NoDocstringError, common.VCSError, common.NoVersionError) as e:
-            sys.exit(e.args[0])
-    elif args.subcmd == 'publish':
-        from .upload import main
-        main(args.ini_file, args.repository, formats=set(args.format or []))
-
-    elif args.subcmd == 'install':
-        from .install import Installer
-        try:
-            Installer(args.ini_file, user=args.user, python=args.python,
-                      symlink=args.symlink, deps=args.deps, extras=args.extras,
-                      pth=args.pth_file).install()
-        except (common.NoDocstringError, common.NoVersionError) as e:
-            sys.exit(e.args[0])
-    elif args.subcmd == 'installfrom':
-        from .installfrom import installfrom
-        sys.exit(installfrom(args.location, user=args.user, python=args.python))
-    elif args.subcmd == 'init':
-        from .init import TerminalIniter
-        TerminalIniter().initialise()
+    if args.subcmd:
+        exitcode = args.subcmd_entrypoint(args)
+        sys.exit(exitcode)
     else:
         ap.print_help()
         sys.exit(1)

flit/subcommand/__init__.py

@@ -0,0 +1,38 @@
+"""
+The "subcommand" package contains implementations for CLI commands in flit.
+
+Subcommands must:
+
+* Contain an implementation in ``flit/subcommand/<name>.py``
+* Be registered using ``flit.subcommand.register`` before parsing the arguments
+
+Each subcommand module must contain the following names:
+
+* NAME: the name of the command which is exposed in the CLI args (this is what
+  the user types to trigger that subcommand).
+* HELP: A short 1-line help which is displayed when the user runs
+  ``flit --help``
+* setup: A callable which sets up the subparsers. As a single argument it gets
+  a reference to the sub-parser. No return required.
+* run: A callable which gets executed when the subcommand is selected by the
+  end-user. As a single argument it gets a reference to the root
+  argument-parser. It should return an integer representing the exit-code of
+  the application.
+"""
+from importlib import import_module
+
+
+def register(main_parser, module_name):
+    """
+    This registers a new subcommand with the main argument parser.
+
+    :param main_parser: A reference to the main argument parser instance.
+    :param module_name: The base-name of the subcommand module. If a module is
+        added as ``flit/subcommand/foo.py``, this should be ``foo``. This value
+        is used to dynamically import the subcommend so it must be a valid
+        module name.
+    """
+    subcmd = import_module('flit.subcommand.%s' % module_name)
+    parser = main_parser.add_parser(subcmd.NAME,help=subcmd.HELP)
+    parser.set_defaults(subcmd_entrypoint=subcmd.run)
+    subcmd.setup(parser)

flit/subcommand/build.py

@@ -0,0 +1,25 @@
+"""
+This module contains the implementation for the "build" subcommand.
+"""
+import sys
+
+from .. import common
+from ..build import main
+
+NAME = 'build'
+HELP = "Build wheel and sdist"
+
+
+def setup(parser):
+    parser.add_argument(
+        '--format', action='append',
+        help="Select a format to build. Options: 'wheel', 'sdist'"
+    )
+
+
+def run(args):
+    try:
+        main(args.ini_file, formats=set(args.format or []))
+    except(common.NoDocstringError, common.VCSError, common.NoVersionError) as e:
+        return e.args[0]
+    return 0

flit/subcommand/info.py

@@ -0,0 +1,27 @@
+"""
+This module contains the implementation for the "info" subcommand
+"""
+
+import sys
+
+from .. import inifile
+from ..common import Module, make_metadata
+
+NAME = 'info'
+HELP = "Retrieve metadata information from the project"
+
+
+def setup(parser):
+    parser.add_argument(
+        '--version', default=False, action='store_true', dest='show_version',
+        help="Print the version number of the project to stdout"
+    )
+
+
+def run(args):
+    ini_info = inifile.read_pkg_ini(args.ini_file)
+    module = Module(ini_info['module'], args.ini_file.parent)
+    metadata = make_metadata(module, ini_info)
+    output = metadata.version
+    print(output)
+    return 0

flit/subcommand/init.py

@@ -0,0 +1,17 @@
+"""
+This module contains the implementation for the "init" subcommand
+"""
+
+from ..init import TerminalIniter
+
+NAME = 'init'
+HELP = "Prepare pyproject.toml for a new package"
+
+
+def setup(parser):
+    pass
+
+
+def run(args):
+    TerminalIniter().initialise()
+    return 0

flit/subcommand/install.py

@@ -0,0 +1,52 @@
+"""
+This module contains the implementation for the "install" subcommand
+
+This module also contains a definition of ``add_shared_install_options`` which
+can be used to set up additional arguments for an "install-type" subcommand.
+"""
+
+import sys
+from ..install import Installer
+from .. import common
+
+NAME = 'install'
+HELP = "Install the package"
+
+
+def add_shared_install_options(parser):
+    parser.add_argument('--user', action='store_true', default=None,
+        help="Do a user-local install (default if site.ENABLE_USER_SITE is True)"
+    )
+    parser.add_argument('--env', action='store_false', dest='user',
+        help="Install into sys.prefix (default if site.ENABLE_USER_SITE is False, i.e. in virtualenvs)"
+    )
+    parser.add_argument('--python', default=sys.executable,
+        help="Target Python executable, if different from the one running flit"
+    )
+
+
+def setup(parser):
+    parser.add_argument('-s', '--symlink', action='store_true',
+        help="Symlink the module/package into site packages instead of copying it"
+    )
+    parser.add_argument('--pth-file', action='store_true',
+        help="Add .pth file for the module/package to site packages instead of copying it"
+    )
+    parser.add_argument('--deps', choices=['all', 'production', 'develop', 'none'], default='all',
+        help="Which set of dependencies to install. If --deps=develop, the extras dev, doc, and test are installed"
+    )
+    parser.add_argument('--extras', default=(), type=lambda l: l.split(',') if l else (),
+        help="Install the dependencies of these (comma separated) extras additionally to the ones implied by --deps. "
+             "--extras=all can be useful in combination with --deps=production, --deps=none precludes using --extras"
+    )
+    add_shared_install_options(parser)
+
+
+def run(args):
+    try:
+        Installer(args.ini_file, user=args.user, python=args.python,
+                    symlink=args.symlink, deps=args.deps, extras=args.extras,
+                    pth=args.pth_file).install()
+    except (common.NoDocstringError, common.NoVersionError) as e:
+        return e.args[0]
+    return 0

flit/subcommand/installfrom.py

@@ -0,0 +1,24 @@
+"""
+This module contains the implementation of the "installfrom" subcommand.
+"""
+
+import sys
+
+from ..installfrom import installfrom
+from .install import add_shared_install_options
+
+NAME = 'installfrom'
+HELP = "Download and install a package using flit from source"
+
+
+def setup(parser):
+    parser.add_argument(
+        'location',
+        help="A URL to download, or a shorthand like github:takluyver/flit"
+    )
+    add_shared_install_options(parser)
+
+
+def run(args):
+    returncode = installfrom(args.location, user=args.user, python=args.python)
+    return returncode

flit/subcommand/publish.py

@@ -0,0 +1,18 @@
+"""
+This module contains the implementation of the "installfrom" subcommand.
+"""
+from ..upload import main
+
+NAME = 'publish'
+HELP = "Upload wheel and sdist"
+
+
+def setup(parser):
+    parser.add_argument('--format', action='append',
+                        help="Select a format to publish. Options: 'wheel', 'sdist'"
+                        )
+
+
+def run(args):
+    main(args.ini_file, args.repository, formats=set(args.format or []))
+    return 0