fix(builder): fixed fluent api for the required rule builder

The required rule builder was in need of 2 optional parameters: path and
errorMessage.
However errorMessage can be specified regardless whether
path is present or not, making the api cumbersome.
Changed the builder
adding the withPath, withErrorMessage and build methods

BREAKING CHANGE: Now the required rule builder requires the build method
to be called

Author: ziccardi

src/example/nestedRulesSample-fluent.ts

@@ -16,12 +16,12 @@ const validator = validatorBuilder()
   .newRule()
   .withField('platform')
   .validate(RuleBuilder.isIn.withValues('MOBILE', 'DESKTOP').build())
-  .validate(RuleBuilder.required())
+  .validate(RuleBuilder.required.build())
   .newRule()
   .withFieldValueConstraint('platform', 'mobile')
   .withField('os')
   .validate(RuleBuilder.isIn.withValues('ANDROID', 'iOS', 'WINDOWS').build())
-  .validate(RuleBuilder.required())
+  .validate(RuleBuilder.required.build())
   .withField('programming_lang')
   .validate(
     RuleBuilder.composite

src/rules/builders/RequiredValueBuilder.ts

@@ -1,9 +1,47 @@
 import {RuleConfig} from '../../config/RuleConfig';
 
+export interface RequiredRuleBuilder {
+  withPath: (path: string) => RequiredRuleBuilder;
+  withErrorMessage: (errorMessage: string) => RequiredRuleBuilder;
+  build: () => RuleConfig;
+}
+
+const createWithPath = (
+  rule: RuleConfig
+): ((path: string) => RequiredRuleBuilder) => {
+  const withPath = (path: string) => {
+    rule.path = path;
+    return {
+      withPath: createWithPath(rule),
+      withErrorMessage: createWithErrorMessage(rule),
+      build: createBuild(rule),
+    };
+  };
+
+  return withPath;
+};
+
+const createWithErrorMessage = (
+  rule: RuleConfig
+): ((path: string) => RequiredRuleBuilder) => {
+  const withErrorMessage = (errorMessage: string) => {
+    rule.errorMessage = errorMessage;
+    return {
+      withPath: createWithPath(rule),
+      withErrorMessage: createWithErrorMessage(rule),
+      build: createBuild(rule),
+    };
+  };
+
+  return withErrorMessage;
+};
+
+const createBuild = (rule: RuleConfig): (() => RuleConfig) => () => rule;
+
 export const builder = {
-  required: (path?: string, errorMessage?: string): RuleConfig => ({
-    type: 'REQUIRED',
-    path,
-    errorMessage,
-  }),
+  required: {
+    withPath: createWithPath({type: 'REQUIRED'}),
+    withErrorMessage: createWithErrorMessage({type: 'REQUIRED'}),
+    build: createBuild({type: 'REQUIRED'}),
+  },
 };