add webfinger.fetch_actor_url, use it in follow

also add a basic test for webfinger.fetch

follow.py

@@ -96,19 +96,8 @@ class FollowCallback(indieauth.Callback):
         addr = state
         if not state:
             error('Missing state')
-        elif util.is_web(state):
-            as2_url = state
-        else:
-            resp = webfinger.fetch(addr)
-            if resp is None:
-                return redirect(g.user.user_page_path('following'))
-
-            as2_url = None
-            for link in resp.get('links', []):
-                type = link.get('type', '').split(';')[0]
-                if link.get('rel') == 'self' and type in as2.CONTENT_TYPES:
-                    as2_url = link.get('href')
 
+        as2_url = state if util.is_web(state) else webfinger.fetch_actor_url(addr)
         if not as2_url:
             flash(f"Couldn't find ActivityPub profile link for {addr}")
             return redirect(g.user.user_page_path('following'))

tests/test_webfinger.py

@@ -10,6 +10,7 @@ from oauth_dropins.webutil.testutil import requests_response
 from .testutil import Fake, TestCase
 
 from web import Web
+from webfinger import fetch, fetch_actor_url
 
 from .test_web import ACTOR_HTML
 
@@ -261,7 +262,7 @@ class WebfingerTest(TestCase):
         self.assertEqual(400, got.status_code, got.get_data(as_text=True))
 
     @patch('requests.get')
-    def test_fetch_create_user(self, mock_get):
+    def test_serve_create_user(self, mock_get):
         self.user.key.delete()
         mock_get.return_value = requests_response(ACTOR_HTML)
 
@@ -282,3 +283,22 @@ class WebfingerTest(TestCase):
 
         got = self.client.get('/.well-known/webfinger?resource=acct%3A%40localhost')
         self.assertEqual(400, got.status_code, got.get_data(as_text=True))
+
+    @patch('requests.get', return_value=requests_response(
+        WEBFINGER, content_type='application/jrd+json'))
+    def test_fetch(self, mock_get):
+        self.assertEqual(WEBFINGER, fetch('@foo@bar'))
+        self.assert_req(mock_get,
+                        'https://bar/.well-known/webfinger?resource=acct:foo@bar')
+
+    @patch('requests.get', return_value=requests_response(WEBFINGER))
+    def test_fetch_actor_url(self, mock_get):
+        self.assertEqual('http://localhost/user.com', fetch_actor_url('@foo@bar'))
+        self.assert_req(mock_get,
+                        'https://bar/.well-known/webfinger?resource=acct:foo@bar')
+
+    @patch('requests.get', return_value=requests_response({'links': []}))
+    def test_fetch_actor_url_not_found(self, mock_get):
+        self.assertIsNone(fetch_actor_url('@foo@bar'))
+        self.assert_req(mock_get,
+                        'https://bar/.well-known/webfinger?resource=acct:foo@bar')

webfinger.py

@@ -1,7 +1,7 @@
 """Handles requests for WebFinger endpoints.
 
-https://webfinger.net/
-https://tools.ietf.org/html/rfc7033
+* https://webfinger.net/
+* https://tools.ietf.org/html/rfc7033
 """
 import logging
 import urllib.parse
@@ -172,17 +172,15 @@ def fetch(addr):
 
     On failure, flashes a message and returns None.
 
-    TODO: unit tests. right now it's only tested indirectly, in test_follow.
     TODO: switch to raising exceptions instead of flashing messages and
     returning None
 
     Args:
-      addr: str, a Webfinger-compatible address, eg @x@y, acct:x@y, or
+      addr (str): a Webfinger-compatible address, eg @x@y, acct:x@y, or
         https://x/y
 
     Returns:
-      dict, fetched Webfinger data, or None on error
-
+      dict: fetched Webfinger data, or None on error
     """
     addr = addr.strip().strip('@')
     split = addr.split('@')
@@ -220,6 +218,28 @@ def fetch(addr):
     return data
 
 
+def fetch_actor_url(addr):
+    """Fetches and returns a WebFinger address's ActivityPub actor URL.
+
+    On failure, flashes a message and returns None.
+
+    Args:
+      addr (str): a Webfinger-compatible address, eg ``@x@y``, ``acct:x@y``, or
+        ``https://x/y``
+
+    Returns:
+      str: ActivityPub actor URL, or None on error or not fouund
+    """
+    data = fetch(addr)
+    if not data:
+        return None
+
+    for link in data.get('links', []):
+        type = link.get('type', '').split(';')[0]
+        if link.get('rel') == 'self' and type in as2.CONTENT_TYPES:
+            return link.get('href')
+
+
 app.add_url_rule('/.well-known/webfinger', view_func=Webfinger.as_view('webfinger'))
 app.add_url_rule('/.well-known/host-meta', view_func=HostMeta.as_view('hostmeta'))
 app.add_url_rule('/.well-known/host-meta.json', view_func=HostMeta.as_view('hostmeta-json'))