fix(config-validator): allow default null val for globalOptions (#27616)

lib/config/validation.spec.ts

@@ -1251,6 +1251,39 @@ describe('config/validation', () => {
         },
       ]);
     });
+
+    it('validates options with different type but defaultValue=null', async () => {
+      const config = {
+        minimumReleaseAge: null,
+        groupName: null,
+        groupSlug: null,
+        dependencyDashboardLabels: null,
+        defaultRegistryUrls: null,
+        registryUrls: null,
+        hostRules: [
+          {
+            artifactAuth: null,
+            concurrentRequestLimit: null,
+            httpsCertificate: null,
+            httpsPrivateKey: null,
+            httpsCertificateAuthority: null,
+          },
+        ],
+        encrypted: null,
+        milestone: null,
+        branchConcurrentLimit: null,
+        hashedBranchLength: null,
+        assigneesSampleSize: null,
+        reviewersSampleSize: null,
+      };
+      const { warnings, errors } = await configValidation.validateConfig(
+        false,
+        // @ts-expect-error: contains invalid values
+        config,
+      );
+      expect(warnings).toHaveLength(0);
+      expect(errors).toHaveLength(0);
+    });
   });
 
   describe('validate globalOptions()', () => {
@@ -1540,5 +1573,25 @@ describe('config/validation', () => {
       expect(warnings).toHaveLength(0);
       expect(errors).toHaveLength(0);
     });
+
+    it('validates options with different type but defaultValue=null', async () => {
+      const config = {
+        onboardingCommitMessage: null,
+        dryRun: null,
+        logContext: null,
+        endpoint: null,
+        skipInstalls: null,
+        autodiscoverFilter: null,
+        autodiscoverNamespaces: null,
+        autodiscoverTopics: null,
+      };
+      const { warnings, errors } = await configValidation.validateConfig(
+        true,
+        // @ts-expect-error: contains invalid values
+        config,
+      );
+      expect(warnings).toHaveLength(0);
+      expect(errors).toHaveLength(0);
+    });
   });
 });

lib/config/validation.ts

@@ -828,6 +828,7 @@ async function validateGlobalConfig(
   warnings: ValidationMessage[],
   currentPath: string | undefined,
 ): Promise<void> {
+  if (val !== null) {
     if (type === 'string') {
       if (is.string(val)) {
         if (
@@ -963,6 +964,7 @@ async function validateGlobalConfig(
         });
       }
     }
+  }
 }
 
 /**  An option is a false global if it has the same name as a global only option