From e108537964a1ec1b1b981248074feb879861bb2c Mon Sep 17 00:00:00 2001
From: Rhys Arkins <rhys@arkins.net>
Date: Mon, 13 Sep 2021 15:27:01 +0200
Subject: [PATCH] fix(config): migrate empty array check (#11713)

---
 lib/config/migration.spec.ts | 11 +++++++++++
 lib/config/migration.ts      | 18 ++++++++++--------
 2 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/lib/config/migration.spec.ts b/lib/config/migration.spec.ts
index 5073963864aa03..462124b8e28b83 100644
--- a/lib/config/migration.spec.ts
+++ b/lib/config/migration.spec.ts
@@ -772,4 +772,15 @@ describe('config/migration', () => {
     expect(isMigrated).toBe(true);
     expect(migratedConfig).toMatchSnapshot();
   });
+  it('migrates empty requiredStatusChecks', () => {
+    const config: RenovateConfig = {
+      requiredStatusChecks: [],
+    };
+    const { isMigrated, migratedConfig } = configMigration.migrateConfig(
+      config,
+      defaultConfig
+    );
+    expect(isMigrated).toBe(true);
+    expect(migratedConfig).toMatchInlineSnapshot(`Object {}`);
+  });
 });
diff --git a/lib/config/migration.ts b/lib/config/migration.ts
index 13497ff59cbd13..1fb49fc3a3caa3 100644
--- a/lib/config/migration.ts
+++ b/lib/config/migration.ts
@@ -490,16 +490,18 @@ export function migrateConfig(
           delete migratedConfig.node;
         }
       } else if (is.array(val)) {
-        const newArray = [];
-        for (const item of migratedConfig[key] as unknown[]) {
-          if (is.object(item) && !is.array(item)) {
-            const arrMigrate = migrateConfig(item as RenovateConfig, key);
-            newArray.push(arrMigrate.migratedConfig);
-          } else {
-            newArray.push(item);
+        if (is.array(migratedConfig?.[key])) {
+          const newArray = [];
+          for (const item of migratedConfig[key] as unknown[]) {
+            if (is.object(item) && !is.array(item)) {
+              const arrMigrate = migrateConfig(item as RenovateConfig, key);
+              newArray.push(arrMigrate.migratedConfig);
+            } else {
+              newArray.push(item);
+            }
           }
+          migratedConfig[key] = newArray;
         }
-        migratedConfig[key] = newArray;
       } else if (key === 'compatibility' && is.object(val)) {
         migratedConfig.constraints = migratedConfig.compatibility;
         delete migratedConfig.compatibility;