Assign new incoming diff lines to the correct view type

Loading diffs for renamed files works slightly differently
than loading other diff files' diffs, so when the FF for
unified diffs was added, this place was missed.

app/assets/javascripts/diffs/store/actions.js

@@ -626,7 +626,7 @@ export function switchToFullDiffFromRenamedFile({ commit, dispatch, state }, { d
     .then(({ data }) => {
       const lines = data.map((line, index) =>
         prepareLineForRenamedFile({
-          diffViewType: state.diffViewType,
+          diffViewType: window.gon?.features?.unifiedDiffLines ? 'inline' : state.diffViewType,
           line,
           diffFile,
           index,
@@ -638,6 +638,7 @@ export function switchToFullDiffFromRenamedFile({ commit, dispatch, state }, { d
         viewer: {
           ...diffFile.alternate_viewer,
           automaticallyCollapsed: false,
+          manuallyCollapsed: false,
         },
       });
       commit(types.SET_CURRENT_VIEW_DIFF_FILE_LINES, { filePath: diffFile.file_path, lines });

app/assets/javascripts/diffs/store/mutations.js

@@ -378,8 +378,13 @@ export default {
   },
   [types.SET_CURRENT_VIEW_DIFF_FILE_LINES](state, { filePath, lines }) {
     const file = state.diffFiles.find(f => f.file_path === filePath);
-    const currentDiffLinesKey =
-      state.diffViewType === 'inline' ? 'highlighted_diff_lines' : 'parallel_diff_lines';
+    let currentDiffLinesKey;
+
+    if (window.gon?.features?.unifiedDiffLines || state.diffViewType === 'inline') {
+      currentDiffLinesKey = 'highlighted_diff_lines';
+    } else {
+      currentDiffLinesKey = 'parallel_diff_lines';
+    }
 
     file[currentDiffLinesKey] = lines;
   },

changelogs/unreleased/defect-collapsed-files-expand-renamed-files.yml

+---
+title: Assign new incoming diff lines for renamed files to the correct view type
+merge_request: 46823
+author:
+type: fixed

spec/frontend/diffs/store/actions_spec.js

@@ -1149,7 +1149,11 @@ describe('DiffsStoreActions', () => {
       file_hash: 'testhash',
       alternate_viewer: { name: updatedViewerName },
     };
-    const updatedViewer = { name: updatedViewerName, automaticallyCollapsed: false };
+    const updatedViewer = {
+      name: updatedViewerName,
+      automaticallyCollapsed: false,
+      manuallyCollapsed: false,
+    };
     const testData = [{ rich_text: 'test' }, { rich_text: 'file2' }];
     let renamedFile;
     let mock;