add OPTIMIZED_COMMENTS constant for whether get_comments() is constan…

…t or linear

for snarfed/bridgy#1021

granary/facebook.py

@@ -214,6 +214,7 @@ class Facebook(source.Source):
   NAME = 'Facebook'
   FRONT_PAGE_TEMPLATE = 'templates/facebook_index.html'
   POST_ID_RE = re.compile('^[0-9_:]+$')  # see parse_id() for gory details
+  OPTIMIZED_COMMENTS = True
 
   # HTML snippet for embedding a post.
   # https://developers.facebook.com/docs/plugins/embedded-posts/

granary/flickr.py

@@ -27,6 +27,7 @@ class Flickr(source.Source):
   DOMAIN = 'flickr.com'
   BASE_URL = 'https://www.flickr.com/'
   NAME = 'Flickr'
+  OPTIMIZED_COMMENTS = False
 
   API_EXTRAS = ','.join(('date_upload', 'date_taken', 'views', 'media',
                          'description', 'tags', 'machine_tags', 'geo',

granary/github.py

@@ -232,7 +232,7 @@ class GitHub(source.Source):
     'use_automatic_links': False,
     'tag_callback': tag_placeholders,
   }
-
+  OPTIMIZED_COMMENTS = True
 
   def __init__(self, access_token=None):
     """Constructor.

granary/instagram.py

@@ -72,6 +72,7 @@ class Instagram(source.Source):
   BASE_URL = 'https://www.instagram.com/'
   NAME = 'Instagram'
   FRONT_PAGE_TEMPLATE = 'templates/instagram_index.html'
+  OPTIMIZED_COMMENTS = False
 
   EMBED_POST = """
   <script async defer src="//platform.instagram.com/en_US/embeds.js"></script>

granary/reddit.py

@@ -22,10 +22,12 @@
 
 
 class Reddit(source.Source):
+  """Reddit source class. See file docstring and Source class for details."""
 
   DOMAIN = 'reddit.com'
   BASE_URL = 'https://reddit.com'
   NAME = 'Reddit'
+  OPTIMIZED_COMMENTS = True
 
   def __init__(self, refresh_token):
     self.refresh_token = refresh_token

granary/source.py

@@ -205,12 +205,15 @@ class Source(object, metaclass=SourceMeta):
         Defaults to Twitter's limit, 280 characters as of 2019-10-12.
   * TRUNCATE_URL_LENGTH: integer, optional. Number of characters that URLs count
         for. Defaults to Twitter's, 23 as of 2019-10-12.
+  * OPTIMIZED_COMMENTS: boolean, whether :meth:`get_comment()` is optimized and
+    only fetches the requested comment. If False, :meth:`get_comment()` fetches
+    many or all of the post's comments to find the requested one.
   """
-
   POST_ID_RE = None
   HTML2TEXT_OPTIONS = {}
   TRUNCATE_TEXT_LENGTH = None
   TRUNCATE_URL_LENGTH = None
+  OPTIMIZED_COMMENTS = False
 
   def user_url(self, user_id):
     """Returns the URL for a user's profile."""

granary/twitter.py

@@ -133,6 +133,7 @@ class Twitter(source.Source):
   NAME = 'Twitter'
   FRONT_PAGE_TEMPLATE = 'templates/twitter_index.html'
   POST_ID_RE = re.compile('^[0-9]+$')
+  OPTIMIZED_COMMENTS = True
 
   # HTML snippet for embedding a tweet.
   # https://dev.twitter.com/docs/embedded-tweets