#188

backend/app/controllers/wiki_pages_controller.rb

@@ -31,17 +31,20 @@ class WikiPagesController < ApplicationController
 
   def diff
     id = params[:id]
-    from = params[:from]
+    return head :bad_request if id.blank?
+
+    from = params[:from].presence
     to = params[:to].presence
-    return head :bad_request if id.blank? || from.blank?
 
     page = WikiPage.find(id)
 
-    from_rev = page.wiki_revisions.find(from)
+    from_rev = from && page.wiki_revisions.find(from)
     to_rev = to ? page.wiki_revisions.find(to) : page.current_revision
-    return head :unprocessable_entity if !(from_rev&.content?) || !(to_rev&.content?)
+    if ((from_rev && !(from_rev.content?)) || !(to_rev&.content?))
+      return head :unprocessable_entity
+    end
 
-    diffs = Diff::LCS.sdiff(from_rev.body.lines, to_rev.body.lines)
+    diffs = Diff::LCS.sdiff(from_rev&.body&.lines || [], to_rev.body.lines)
     diff_json = diffs.map { |change|
       case change.action
       when ?=
@@ -58,7 +61,7 @@ class WikiPagesController < ApplicationController
 
     render json: { wiki_page_id:      page.id,
                    title:             page.title,
-                   older_revision_id: from_rev.id,
+                   older_revision_id: from_rev&.id,
                    newer_revision_id: to_rev.id,
                    diff:              diff_json }
   end