2 files changed, 61 insertions, 0 deletions

diff --git a/app/assets/javascripts/diffs/store/getters.js b/app/assets/javascripts/diffs/store/getters.js
index 855de79adf8..d3881fa1a0a 100644
--- a/app/assets/javascripts/diffs/store/getters.js
+++ b/app/assets/javascripts/diffs/store/getters.js
@@ -1,5 +1,7 @@
 import _ from 'underscore';
+import { convertObjectPropsToCamelCase } from '~/lib/utils/common_utils';
 import { PARALLEL_DIFF_VIEW_TYPE, INLINE_DIFF_VIEW_TYPE } from '../constants';
+import { getDiffRefsByLineCode } from './utils';
 
 export const isParallelView = state => state.diffViewType === PARALLEL_DIFF_VIEW_TYPE;
 
@@ -56,6 +58,44 @@ export const getDiffFileDiscussions = (state, getters, rootState, rootGetters) =
       discussion.diff_discussion && _.isEqual(discussion.diff_file.file_hash, diff.fileHash),
   ) || [];
 
+/**
+ * Returns an Object with discussions by their diff line code
+ * To avoid rendering outdated discussions on the Changes tab we should do a bunch of SHA
+ * comparisions. `note.position.formatter` have the current version diff refs but
+ * `note.original_position.formatter` will have the first version's diff refs.
+ * If line diff refs matches with one of them, we should render it as a discussion on Changes tab.
+ *
+ * @param {Object} diff
+ * @returns {Array}
+ */
+export const discussionsByLineCode = (state, getters, rootState, rootGetters) => {
+  const diffRefsByLineCode = getDiffRefsByLineCode(state.diffFiles);
+
+  return rootGetters.discussions.reduce((acc, note) => {
+    const isDiffDiscussion = note.diff_discussion;
+    const hasLineCode = note.line_code;
+    const isResolvable = note.resolvable;
+    const diffRefs = diffRefsByLineCode[note.line_code];
+
+    if (isDiffDiscussion && hasLineCode && isResolvable && diffRefs) {
+      const refs = convertObjectPropsToCamelCase(note.position.formatter);
+      const originalRefs = convertObjectPropsToCamelCase(note.original_position.formatter);
+
+      if (_.isEqual(refs, diffRefs) || _.isEqual(originalRefs, diffRefs)) {
+        const lineCode = note.line_code;
+
+        if (acc[lineCode]) {
+          acc[lineCode].push(note);
+        } else {
+          acc[lineCode] = [note];
+        }
+      }
+    }
+
+    return acc;
+  }, {});
+};
+
 // prevent babel-plugin-rewire from generating an invalid default during karma∂ tests
 export const getDiffFileByHash = state => fileHash =>
   state.diffFiles.find(file => file.fileHash === fileHash);
diff --git a/app/assets/javascripts/diffs/store/utils.js b/app/assets/javascripts/diffs/store/utils.js
index d9589baa76e..82082ac508a 100644
--- a/app/assets/javascripts/diffs/store/utils.js
+++ b/app/assets/javascripts/diffs/store/utils.js
@@ -173,3 +173,24 @@ export function trimFirstCharOfLineContent(line = {}) {
 
   return parsedLine;
 }
+
+export function getDiffRefsByLineCode(diffFiles) {
+  return diffFiles.reduce((acc, diffFile) => {
+    const { baseSha, headSha, startSha } = diffFile.diffRefs;
+    const { newPath, oldPath } = diffFile;
+
+    // We can only use highlightedDiffLines to create the map of diff lines because
+    // highlightedDiffLines will also include every parallel diff line in it.
+    if (diffFile.highlightedDiffLines) {
+      diffFile.highlightedDiffLines.forEach(line => {
+        const { lineCode, oldLine, newLine } = line;
+
+        if (lineCode) {
+          acc[lineCode] = { baseSha, headSha, startSha, newPath, oldPath, oldLine, newLine };
+        }
+      });
+    }
+
+    return acc;
+  }, {});
+}