Show correct size when MR diff overflowsmr-diff-size-overflow

The problem is that we often go via a diff object constructed from the diffs
stored in the DB. Those diffs, by definition, don't overflow, so we don't have
access to the 'correct' `real_size` - that is stored on the MR diff object
iself.

2 files changed, 10 insertions, 9 deletions

diff --git a/app/models/merge_request.rb b/app/models/merge_request.rb
index 1d4827375d7..9d2288c311e 100644
--- a/app/models/merge_request.rb
+++ b/app/models/merge_request.rb
@@ -191,22 +191,23 @@ class MergeRequest < ActiveRecord::Base
     merge_request_diff ? merge_request_diff.raw_diffs(*args) : compare.raw_diffs(*args)
   end
 
-  def diffs(diff_options = nil)
+  def diffs(diff_options = {})
     if compare
-      compare.diffs(diff_options)
+      # When saving MR diffs, `no_collapse` is implicitly added (because we need
+      # to save the entire contents to the DB), so add that here for
+      # consistency.
+      compare.diffs(diff_options.merge(no_collapse: true))
     else
       merge_request_diff.diffs(diff_options)
     end
   end
 
   def diff_size
-    # The `#diffs` method ends up at an instance of a class inheriting from
-    # `Gitlab::Diff::FileCollection::Base`, so use those options as defaults
-    # here too, to get the same diff size without performing highlighting.
-    #
-    opts = Gitlab::Diff::FileCollection::Base.default_options.merge(diff_options || {})
+    # Calling `merge_request_diff.diffs.real_size` will also perform
+    # highlighting, which we don't need here.
+    return real_size if merge_request_diff
 
-    raw_diffs(opts).size
+    diffs.real_size
   end
 
   def diff_base_commit
diff --git a/app/models/merge_request_diff.rb b/app/models/merge_request_diff.rb
index 6604af2b47e..f0a3c30ea74 100644
--- a/app/models/merge_request_diff.rb
+++ b/app/models/merge_request_diff.rb
@@ -260,7 +260,7 @@ class MergeRequestDiff < ActiveRecord::Base
       new_attributes[:state] = :empty
     else
       diff_collection = compare.diffs(Commit.max_diff_options)
-      new_attributes[:real_size] = compare.diffs.real_size
+      new_attributes[:real_size] = diff_collection.real_size
 
       if diff_collection.any?
         new_diffs = dump_diffs(diff_collection)