fix: raise config errors for package rules missing selectors

lib/config/validation.js

@@ -141,12 +141,12 @@ async function validateConfig(config) {
                     }
                   }
                   if (!hasSelector) {
-                    const message =
-                      'Each packageRule must contain at least one of ' +
-                      JSON.stringify(selectors);
+                    const message = `Each packageRule must contain at least one selector (${selectors.join(
+                      ', '
+                    )}). If you wish for configuration to apply to all packages, it is not necessary to place it inside a packageRule at all.`;
                     logger.info({ packageRule }, `packageRule warning`);
-                    warnings.push({
-                      depName: 'Configuration Warning',
+                    errors.push({
+                      depName: 'Configuration Error',
                       message,
                     });
                   }

test/config/__snapshots__/validation.spec.js.snap

 // Jest Snapshot v1, https://goo.gl/fbAQLP
 
 exports[`config/validation validateConfig(config) errors for all types 1`] = `
-Array [
-  Object {
-    "depName": "Configuration Warning",
-    "message": "Each packageRule must contain at least one of [\\"packageNames\\",\\"packagePatterns\\",\\"excludePackageNames\\",\\"excludePackagePatterns\\"]",
-  },
-]
-`;
-
-exports[`config/validation validateConfig(config) errors for all types 2`] = `
 Array [
   Object {
     "depName": "Configuration Error",
@@ -47,6 +38,10 @@ Array [
     "depName": "Configuration Error",
     "message": "Invalid configuration option: \`foo\`",
   },
+  Object {
+    "depName": "Configuration Error",
+    "message": "Each packageRule must contain at least one selector (packageNames, packagePatterns, excludePackageNames, excludePackagePatterns). If you wish for configuration to apply to all packages, it is not necessary to place it inside a packageRule at all.",
+  },
   Object {
     "depName": "Configuration Error",
     "message": "packageRules must contain JSON objects",

test/config/validation.spec.js

@@ -43,10 +43,9 @@ describe('config/validation', () => {
       const { warnings, errors } = await configValidation.validateConfig(
         config
       );
-      expect(warnings).toMatchSnapshot();
-      expect(warnings).toHaveLength(1);
+      expect(warnings).toHaveLength(0);
       expect(errors).toMatchSnapshot();
-      expect(errors).toHaveLength(10);
+      expect(errors).toHaveLength(11);
     });
   });
 });