Teach pbr to read extras and env markers

This adds support for reading extras from setup.cfg.

It also adds support for handling environment markers, both in the
extras section and in install_requires and in requirements.txt.

Change-Id: I6fd8276012e65f82934df9c374613b1ce6856b5a

pbr/util.py

@@ -280,6 +280,10 @@ def setup_cfg_to_setup_kwargs(config):
 
     kwargs = {}
 
+    # Temporarily holds install_reqires and extra_requires while we
+    # parse env_markers.
+    all_requirements = {}
+
     for arg in D1_D2_SETUP_ARGS:
         if len(D1_D2_SETUP_ARGS[arg]) == 2:
             # The distutils field name is different than distutils2's.
@@ -326,6 +330,17 @@ def setup_cfg_to_setup_kwargs(config):
                 # setuptools
                 in_cfg_value = [_VERSION_SPEC_RE.sub(r'\1\2', pred)
                                 for pred in in_cfg_value]
+            if arg == 'install_requires':
+                # Split install_requires into package,env_marker tuples
+                # These will be re-assembled later
+                install_requires = []
+                requirement_pattern = '(?P<package>[^;]*);?(?P<env_marker>.*)$'
+                for requirement in in_cfg_value:
+                    m = re.match(requirement_pattern, requirement)
+                    requirement_package = m.group('package').strip()
+                    env_marker = m.group('env_marker').strip()
+                    install_requires.append((requirement_package,env_marker))
+                all_requirements[''] = install_requires
             elif arg == 'package_dir':
                 in_cfg_value = {'': in_cfg_value}
             elif arg in ('package_data', 'data_files'):
@@ -367,6 +382,50 @@ def setup_cfg_to_setup_kwargs(config):
 
         kwargs[arg] = in_cfg_value
 
+    # Transform requirements with embedded environment markers to
+    # setuptools' supported marker-per-requirement format.
+    #
+    # install_requires are treated as a special case of extras, before
+    # being put back in the expected place
+    #
+    # fred =
+    #     foo:marker
+    #     bar
+    # -> {'fred': ['bar'], 'fred:marker':['foo']}
+
+    if 'extras' in config:
+        requirement_pattern = '(?P<package>[^:]*):?(?P<env_marker>.*)$'
+        extras = config['extras']
+        for extra in extras:
+            extra_requirements = []
+            requirements = split_multiline(extras[extra])
+            for requirement in requirements:
+                m = re.match(requirement_pattern, requirement)
+                extras_value = m.group('package').strip()
+                env_marker = m.group('env_marker')
+                extra_requirements.append((extras_value,env_marker))
+            all_requirements[extra] = extra_requirements
+
+    # Transform the full list of requirements into:
+    # - install_requires, for those that have no extra and no
+    #   env_marker
+    # - named extras, for those with an extra name (which may include
+    #   an env_marker)
+    # - and as a special case, install_requires with an env_marker are
+    #   treated as named extras where the name is the empty string
+
+    extras_require = {}
+    for req_group in all_requirements:
+        for requirement, env_marker in all_requirements[req_group]:
+            if env_marker:
+                extras_key = '%s:%s' % (req_group, env_marker)
+            else:
+                extras_key = req_group
+            extras_require.setdefault(extras_key, []).append(requirement)
+
+    kwargs['install_requires'] = extras_require.pop('', [])
+    kwargs['extras_require'] = extras_require
+
     return kwargs