fix(@hapi/joi): fix extend typings (#42297)

types/hapi__joi/hapi__joi-tests.ts

@@ -1012,11 +1012,18 @@ const Joi3 = Joi.extend({
         asd: {
             args: [
                 {
-                    name: 'allowFalse'
+                    name: 'allowFalse',
+                    ref: true,
+                    assert: Joi.boolean(),
                 }
             ],
-            method(allowFalse) {
-                this.$_createError(str, {}, {}, {}, {});
+            method(allowFalse: boolean) {
+                return this.$_addRule({
+                    name: 'asd',
+                    args: {
+                        allowFalse,
+                    }
+                });
             },
             validate(value: boolean, helpers, params, options) {
                 if (value || params.allowFalse && !value) {

types/hapi__joi/index.d.ts

@@ -679,6 +679,13 @@ declare namespace Joi {
 
     type SchemaFunction = (schema: Schema) => Schema;
 
+    interface AddRuleOptions {
+        name: string;
+        args?: {
+            [key: string]: any;
+        };
+    }
+
     interface SchemaInternals {
         /**
          * Parent schema object.
@@ -693,7 +700,7 @@ declare namespace Joi {
         /**
          * Adds a rule to current validation schema.
          */
-        $_addRule(rule: string | ExtensionRule): Schema;
+        $_addRule(rule: string | AddRuleOptions): Schema;
 
         /**
          * Internally compiles schema.
@@ -1756,7 +1763,7 @@ declare namespace Joi {
     interface RuleArgs {
         name: string;
         ref?: boolean;
-        assert?: (value: any) => boolean;
+        assert?: ((value: any) => boolean) | AnySchema;
         message?: string;
 
         /**