New target description + moving target stuff under "framework"

Changing the way target descriptions work from a static mapping to
something that is dynamically generated and is extensible via plugins.
Also moving core target implementation stuff under "framework".

wa/commands/list.py

@@ -0,0 +1,106 @@
+#    Copyright 2014-2015 ARM Limited
+#
+# 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.
+#
+
+from wa import Command, settings
+from wa.framework import pluginloader
+from wa.framework.plugin import PluginLoader
+from wa.framework.target.descriptor import get_target_descriptions
+from wa.utils.doc import get_summary
+from wa.utils.formatter import DescriptionListFormatter
+
+
+class ListCommand(Command):
+
+    name = 'list'
+    description = 'List available WA plugins with a short description of each.'
+
+    def initialize(self, context):
+        kinds = get_kinds()
+        self.parser.add_argument('kind', metavar='KIND',
+                                 help=('Specify the kind of plugin to list. Must be '
+                                       'one of: {}'.format(', '.join(kinds))),
+                                 choices=kinds)
+        self.parser.add_argument('-n', '--name', 
+                                 help='Filter results by the name specified')
+        self.parser.add_argument('-o', '--packaged-only', action='store_true',
+                                 help='''
+                                 Only list plugins packaged with WA itself. Do
+                                 not list plugins installed locally or from
+                                 other packages.
+                                 ''')
+        self.parser.add_argument('-p', '--platform', 
+                                 help='''
+                                 Only list results that are supported by the
+                                 specified platform.
+                                 ''')
+
+    def execute(self, state, args):
+        filters = {}
+        if args.name:
+            filters['name'] = args.name
+
+        if args.kind == 'targets':
+            list_targets()
+        else:
+            list_plugins(args, filters)
+
+
+def get_kinds():
+    kinds = pluginloader.kinds
+    if 'target_descriptor' in kinds:
+        kinds.remove('target_descriptor')
+        kinds.append('target')
+    return ['{}s'.format(name) for name in kinds]
+
+
+def list_targets():
+    targets = get_target_descriptions()
+    targets = sorted(targets, key=lambda x: x.name)
+
+    output = DescriptionListFormatter()
+    for target in targets:
+        output.add_item(target.description or '', target.name)
+    print output.format_data()
+
+
+def list_plugins(args, filters):
+    results = pluginloader.list_plugins(args.kind[:-1])
+    if filters or args.platform:
+        filtered_results = []
+        for result in results:
+            passed = True
+            for k, v in filters.iteritems():
+                if getattr(result, k) != v:
+                    passed = False
+                    break
+            if passed and args.platform:
+                passed = check_platform(result, args.platform)
+            if passed:
+                filtered_results.append(result)
+    else:  # no filters specified
+        filtered_results = results
+
+    if filtered_results:
+        output = DescriptionListFormatter()
+        for result in sorted(filtered_results, key=lambda x: x.name):
+            output.add_item(get_summary(result), result.name)
+        print output.format_data()
+
+
+def check_platform(plugin, platform):
+    supported_platforms = getattr(plugin, 'supported_platforms', [])
+    if supported_platforms:
+        return platform in supported_platforms
+    return True