Add options to control extension reporting output

asdf/commands/extension.py

@@ -5,6 +5,7 @@
 Implementation of command for reporting information about installed extensions.
 """
 
+import sys
 from pkg_resources import iter_entry_points
 
 from .main import Command
@@ -18,12 +19,24 @@ def setup_arguments(cls, subparsers):
             "extensions", help="Show information about installed extensions",
             description="""Reports information about installed ASDF extensions""")
 
+        parser.add_argument(
+            "-s", "--summary", action="store_true",
+            help="Display only the installed extensions themselves")
+        parser.add_argument(
+            "-t", "--tags-only", action="store_true",
+            help="Display tags from installed extensions, but no other information")
+
         parser.set_defaults(func=cls.run)
         return parser
 
     @classmethod
     def run(cls, args):
-        return find_extensions()
+        if args.summary and args.tags_only:
+            sys.stderr.write(
+                "ERROR: Options -s/--summary and -t/--tags-only are not compatible\n")
+            return 1
+
+        return find_extensions(args.summary, args.tags_only)
 
 
 def _format_entry_point(ep):
@@ -40,17 +53,21 @@ def _tag_comparator(a, b):
     return _format_type_name(a) < _format_type_name(b)
 
 
-def find_extensions():
-
-    for ep in iter_entry_points(group='asdf_extensions'):
-        print(_format_entry_point(ep))
-        ext = ep.load()()
-        for typ in sorted(ext.types, key=lambda x: _format_type_name(x)):
-            if typ.name is not None:
-                print("-  " + _format_type_name(typ))
+def _print_extension_details(ext, tags_only):
+    for typ in sorted(ext.types, key=lambda x: _format_type_name(x)):
+        if typ.name is not None:
+            print("-  " + _format_type_name(typ))
+            if not tags_only:
                 print("      implements: {}".format(typ.make_yaml_tag(typ.name)))
                 if typ.types:
                     print("      serializes:")
                     for name in typ.types:
                         print("      - {}".format(_format_type_name(name)))
-        print()
+
+
+def find_extensions(summary, tags_only):
+    for ep in iter_entry_points(group='asdf_extensions'):
+        print(_format_entry_point(ep))
+        if not summary:
+            _print_extension_details(ep.load()(), tags_only)
+            print()