Report max 50 file comments to github

The github api limits us to report 50 file comments per api
request. Since the check run reporting is in the critical path don't
do paging but limit this to 50 comments. In order to get a diverse
feedback sort the messages by 'uniqueness' first so that 100 equal
comments don't push out 5 other comments that are valuable.

Change-Id: If5a7c246a58b510d8fcfa31bd71d74c84acbc278

1 files changed, 26 insertions, 2 deletions

diff --git a/zuul/driver/github/githubconnection.py b/zuul/driver/github/githubconnection.py
index 2d1db034c..c7943fa6b 100644
--- a/zuul/driver/github/githubconnection.py
+++ b/zuul/driver/github/githubconnection.py
@@ -22,7 +22,8 @@ import queue
 import threading
 import time
 import json
-from collections import OrderedDict
+from collections import OrderedDict, defaultdict
+from itertools import chain
 from json.decoder import JSONDecodeError
 from typing import List, Optional
 
@@ -2165,7 +2166,30 @@ class GithubConnection(CachedBranchConnection):
                     continue
 
                 annotations.append(annotation)
-        return annotations
+
+        def _sortUniqueness(annotations):
+            """
+            This method is intended to spread the annotations by uniqueness
+            so we have an as diverse as possible list of annotations.
+            """
+            # First group
+            per_message = defaultdict(list)
+            for annotation in annotations:
+                per_message[annotation['message']].append(annotation)
+
+            # Sort the lists by length. This way we get the messages that
+            # occur less frequently at first.
+            annotation_lists = sorted(list(per_message.values()),
+                                      key=lambda l: len(l))
+
+            return list(chain(*annotation_lists))
+
+        if len(annotations) > 50:
+            # We cannot report more than 50 file comments so sort them by
+            # uniqueness in order to give the user a diverse set of annotations
+            annotations = _sortUniqueness(annotations)
+
+        return annotations[:50]
 
     def getPushedFileNames(self, event):
         files = set()