Optimize collect array of roots (#9165)

jestjs · Nov 11, 2019 · 2cde649 · 2cde649
1 parent 70546e0
commit 2cde649
Showing 1 changed file with 6 additions and 1 deletion.
diff --git a/packages/jest-core/src/getChangedFilesPromise.ts b/packages/jest-core/src/getChangedFilesPromise.ts
@@ -16,7 +16,12 @@ export default (
 ): ChangedFilesPromise | undefined => {
   if (globalConfig.onlyChanged) {
     const allRootsForAllProjects = configs.reduce<Array<Config.Path>>(
-      (roots, config) => [...roots, ...(config.roots || [])],
+      (roots, config) => {
+        if (config.roots) {
+          roots.push(...config.roots);
+        }
+        return roots;
+      },
       [],
     );
     return getChangedFilesForRoots(allRootsForAllProjects, {