Add reqs2pkg

This tool reads in one or more python requirements files and generates
a list of distribution specific package names  the intent is to use it
something like:

  sudo ${package_manager} install $(deps2pkg -r requirements.txt -b)
  sudo pip install .

To install a python project that runs against the distribution provided
pagages rather than pypi wheels/dists

Change-Id: Icd0720311e7863190b84aa916f13e7efa830a4eb

pymod2pkg/cli/reqs2pkg.py

@@ -0,0 +1,115 @@
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import argparse
+import distro
+import packaging.requirements
+import pymod2pkg
+import sys
+
+
+def get_default_prefix(dist):
+    d_lower = dist.lower()
+    if 'ubuntu' in d_lower:
+        return "Depends"
+    return "Requires"
+
+
+def main():
+    """Process python requirements files into a list of distribution
+       packages"""
+    parser = argparse.ArgumentParser(
+        description='Process python requirements files into a list of '
+                    'distribution packages'
+    )
+    parser.add_argument(
+        '--dist', help='distribution style (default: %(default)s)',
+        default=distro.LinuxDistribution().id().partition(' ')[0])
+    parser.add_argument('--pyver', help='Python versions to return. "py" is '
+                        'the unversioned name',
+                        action='append', choices=['py', 'py2', 'py3'],
+                        default=[])
+    parser.add_argument('-r', '--requirements', action="append",
+                        dest='requirements', required=True, default=[],
+                        help="python requirements file to parse")
+    parser.add_argument('-v', '--verbose', dest='verbose', action='count',
+                        default=1, help='Invrease verbosity of the program')
+    parser.add_argument('-b', '--brief', dest='verbose', action='store_const',
+                        const=0, help='Only generate packagenames')
+    parser.add_argument('--prefix', dest='prefix', nargs='?', const=None,
+                        help="Prefix the output with a string provided by "
+                        "the user or one determined by the --dist value")
+
+    args = vars(parser.parse_args())
+
+    pyversions = args['pyver'] if args['pyver'] else ['py']
+    if len(pyversions) > 1:
+        print("Please select only one version of python", file=sys.stderr)
+        return 1
+    args['prefix'] = get_default_prefix(args['dist'])
+
+    for reqs_file in args['requirements']:
+        if args['verbose']:
+            print(f'Processing: {reqs_file}')
+        try:
+            with open(reqs_file) as f:
+                reqs_txt = [line.strip() for line in f.readlines()]
+        except FileNotFoundError as ex:
+            print(ex)
+
+        reqs = []
+        for line in reqs_txt:
+            if line.startswith('#') or line == '':
+                continue
+            # TODO(tonyb): Do we need to extend this so that it does the
+            # right thing when given muliple versions of python for example:
+            # requirements,txt":
+            # liba>2;python_version>=3
+            # altlib;python_version<3
+            # We should honor this based on pyversions
+            req = packaging.requirements.Requirement(line.split('#')[0])
+            pkg = pymod2pkg.module2package(req.name, args['dist'],
+                                           py_vers=pyversions)
+            # We can potentially extend this to include versions
+            # specifications.  The exact output will clearly be
+            # distribution specific
+            reqs.append(pkg)
+
+        # This is slightly complex but it handles the following scenarios:
+        # $ reqs2pkg -r test-requirements.txt --dist ubuntu -b
+        # python-stestr
+        # python-testresources
+        # python-testtools
+        # $ reqs2pkg -r test-requirements.txt --dist ubuntu
+        # Processing: test-requirements.txt
+        # Depends: python-stestr, python-testresources, python-testtools
+        # $ reqs2pkg -r test-requirements.txt --dist rhel -b
+        # python-stestr
+        # python-testresources
+        # python-testtools
+        # $ reqs2pkg -r test-requirements.txt --dist rhel
+        # Processing: test-requirements.txt
+        # Requires: python-stestr
+        # Requires: python-testresources
+        # Requires: python-testtools
+        prefix = ''
+        if args['verbose']:
+            prefix = f"{args['prefix']}: "
+        if args['dist'].lower() in 'ubuntu':
+            delim = ", "
+        else:
+            delim = f"\n{prefix}"
+
+        if args['verbose']:
+            print(prefix + delim.join(reqs))
+        else:
+            print("\n".join(reqs))

setup.cfg

@@ -20,6 +20,7 @@ classifier =
 [entry_points]
 console_scripts =
     pymod2pkg = pymod2pkg.cli.pymod2pkg:main
+    reqs2pkg = pymod2pkg.cli.reqs2pkg:main
 
 [files]
 packages =