fix(cognito): user pool - link style email verification fails to deploy

A couple of things happen with this change -
- `emailVerificationMessage`, `emailVerificationSubject` and
`smsVerificationMessage` properties are not set when link-style
verification is used. This is root cause for the error message reported
by the user.
- The defaults `emailBody` and `emailSubject` are modified when
link-style verification is used. They will now correctly contian the
template placeholder '{##Verify Email##}'.

fixes #6811

Author: Niranjan Jayakar

packages/@aws-cdk/aws-cognito/lib/user-pool.ts

@@ -144,7 +144,9 @@ export interface UserVerificationConfig {
    * The email body template for the verification email sent to the user upon sign up.
    * See https://docs.aws.amazon.com/cognito/latest/developerguide/cognito-user-pool-settings-message-templates.html to
    * learn more about message templates.
-   * @default 'Hello {username}, Your verification code is {####}'
+   *
+   * @default - 'Hello {username}, Your verification code is {####}' if VerificationEmailStyle.CODE is chosen,
+   * 'Hello {username}, Verify your account by clicking on {##Verify Email##}' if VerificationEmailStyle.LINK is chosen.
    */
   readonly emailBody?: string;
 
@@ -159,7 +161,9 @@ export interface UserVerificationConfig {
    * The message template for the verification SMS sent to the user upon sign up.
    * See https://docs.aws.amazon.com/cognito/latest/developerguide/cognito-user-pool-settings-message-templates.html to
    * learn more about message templates.
-   * @default 'The verification code to your new account is {####}'
+   *
+   * @default - 'The verification code to your new account is {####}' if VerificationEmailStyle.CODE is chosen,
+   * not configured if VerificationEmailStyle.LINK is chosen
    */
   readonly smsMessage?: string;
 }
@@ -486,24 +490,15 @@ export class UserPool extends Resource implements IUserPool {
       }
     }
 
-    const emailVerificationSubject = props.userVerification?.emailSubject ?? 'Verify your new account';
-    const emailVerificationMessage = props.userVerification?.emailBody ?? 'Hello {username}, Your verification code is {####}';
-    const smsVerificationMessage = props.userVerification?.smsMessage ?? 'The verification code to your new account is {####}';
-
-    const defaultEmailOption = props.userVerification?.emailStyle ?? VerificationEmailStyle.CODE;
-    const verificationMessageTemplate: CfnUserPool.VerificationMessageTemplateProperty =
-      (defaultEmailOption === VerificationEmailStyle.CODE) ? {
-        defaultEmailOption,
-        emailMessage: emailVerificationMessage,
-        emailSubject: emailVerificationSubject,
-        smsMessage: smsVerificationMessage,
-      } : {
-        defaultEmailOption,
-        emailMessageByLink: emailVerificationMessage,
-        emailSubjectByLink: emailVerificationSubject,
-        smsMessage: smsVerificationMessage
-      };
-
+    const verificationMessageTemplate = this.verificationMessageConfiguration(props);
+    let emailVerificationMessage;
+    let emailVerificationSubject;
+    let smsVerificationMessage;
+    if (verificationMessageTemplate.defaultEmailOption === VerificationEmailStyle.CODE) {
+      emailVerificationMessage = verificationMessageTemplate.emailMessage;
+      emailVerificationSubject = verificationMessageTemplate.emailSubject;
+      smsVerificationMessage = verificationMessageTemplate.smsMessage;
+    }
     const inviteMessageTemplate: CfnUserPool.InviteMessageTemplateProperty = {
       emailMessage: props.userInvitation?.emailBody,
       emailSubject: props.userInvitation?.emailSubject,
@@ -664,6 +659,42 @@ export class UserPool extends Resource implements IUserPool {
     });
   }
 
+  private verificationMessageConfiguration(props: UserPoolProps): CfnUserPool.VerificationMessageTemplateProperty {
+    const emailStyle = props.userVerification?.emailStyle ?? VerificationEmailStyle.CODE;
+    const emailSubject = props.userVerification?.emailSubject ?? 'Verify your new account';
+
+    if (emailStyle === VerificationEmailStyle.CODE) {
+      const emailMessage = props.userVerification?.emailBody ?? 'Hello {username}, Your verification code is {####}';
+      const smsMessage = props.userVerification?.smsMessage ?? 'The verification code to your new account is {####}';
+      if (emailMessage.indexOf('{####}') < 0) {
+        throw new Error(`Verification email body must contain the template string '{####}'`);
+      }
+      if (smsMessage.indexOf('{####}') < 0) {
+        throw new Error(`SMS message must contain the template string '{####}'`);
+      }
+      return {
+        defaultEmailOption: VerificationEmailStyle.CODE,
+        emailMessage,
+        emailSubject,
+        smsMessage,
+      };
+    } else {
+      if (props.userVerification?.smsMessage !== undefined) {
+        throw new Error('SMS message cannot be configured when emailStyle is configured to CODE');
+      }
+      const emailMessage = props.userVerification?.emailBody ?? 'Hello {username}, Verify your account by clicking on {##Verify Email##}';
+      if (emailMessage.indexOf('{##Verify Email##}') < 0) {
+        throw new Error(`Verification email body must contain the template string '{##Verify Email##}'`);
+      }
+      return {
+        defaultEmailOption: VerificationEmailStyle.LINK,
+        emailMessageByLink: emailMessage,
+        emailSubjectByLink: emailSubject,
+        smsMessage: props.userVerification?.smsMessage,
+      };
+    }
+  }
+
   private signInConfiguration(props: UserPoolProps) {
     let aliasAttrs: string[] | undefined;
     let usernameAttrs: string[] | undefined;

packages/@aws-cdk/aws-cognito/test/user-pool.test.ts

@@ -96,22 +96,81 @@ describe('User Pool', () => {
     // WHEN
     new UserPool(stack, 'Pool', {
       userVerification: {
-        emailStyle: VerificationEmailStyle.LINK
+        emailStyle: VerificationEmailStyle.LINK,
       }
     });
 
     // THEN
     expect(stack).toHaveResourceLike('AWS::Cognito::UserPool', {
-      EmailVerificationMessage: 'Hello {username}, Your verification code is {####}',
-      EmailVerificationSubject: 'Verify your new account',
+      EmailVerificationMessage: ABSENT,
+      EmailVerificationSubject: ABSENT,
+      SmsVerificationMessage: ABSENT,
       VerificationMessageTemplate: {
         DefaultEmailOption: 'CONFIRM_WITH_LINK',
-        EmailMessageByLink: 'Hello {username}, Your verification code is {####}',
+        EmailMessageByLink: 'Hello {username}, Verify your account by clicking on {##Verify Email##}',
         EmailSubjectByLink: 'Verify your new account',
+        SmsMessage: ABSENT,
       }
     });
   }),
 
+  test('sms message cannot be specified if link-style email verification is configured', () => {
+    const stack = new Stack();
+
+    expect(() => new UserPool(stack, 'Pool', {
+      userVerification: {
+        emailStyle: VerificationEmailStyle.LINK,
+        smsMessage: 'sms message'
+      }
+    })).toThrow(/SMS message cannot be configured/);
+  });
+
+  test('email and sms verification messages are validated', () => {
+    const stack = new Stack();
+
+    expect(() => new UserPool(stack, 'Pool1', {
+      userVerification: {
+        emailStyle: VerificationEmailStyle.CODE,
+        emailBody: 'invalid email body',
+      }
+    })).toThrow(/Verification email body/);
+
+    expect(() => new UserPool(stack, 'Pool2', {
+      userVerification: {
+        emailStyle: VerificationEmailStyle.CODE,
+        emailBody: 'valid email body {####}',
+      }
+    })).not.toThrow();
+
+    expect(() => new UserPool(stack, 'Pool3', {
+      userVerification: {
+        emailStyle: VerificationEmailStyle.CODE,
+        smsMessage: 'invalid sms message',
+      }
+    })).toThrow(/SMS message/);
+
+    expect(() => new UserPool(stack, 'Pool4', {
+      userVerification: {
+        emailStyle: VerificationEmailStyle.CODE,
+        smsMessage: 'invalid sms message {####}',
+      }
+    })).not.toThrow();
+
+    expect(() => new UserPool(stack, 'Pool5', {
+      userVerification: {
+        emailStyle: VerificationEmailStyle.LINK,
+        emailBody: 'invalid email body {####}',
+      }
+    })).toThrow(/Verification email body/);
+
+    expect(() => new UserPool(stack, 'Pool6', {
+      userVerification: {
+        emailStyle: VerificationEmailStyle.LINK,
+        emailBody: 'invalid email body {##Verify Email##}',
+      }
+    })).not.toThrow();
+  });
+
   test('user invitation messages are configured correctly', () => {
     // GIVEN
     const stack = new Stack();