chore: copy data argument to avoid mutate origin.

packages/mail/src/classes/mail-service.js

@@ -180,20 +180,21 @@ class MailService {
     //Send mail
     try {
 
+      // copy object to avoid mutating original
+      const args = { ...data };
       //Append multiple flag to data if not set
       if (typeof data.isMultiple === 'undefined') {
-        data.isMultiple = isMultiple;
+        args.isMultiple = isMultiple;
       }
 
       //Append global substitution wrappers if not set in data
       if (typeof data.substitutionWrappers === 'undefined') {
-        data.substitutionWrappers = this.substitutionWrappers;
+        args.substitutionWrappers = this.substitutionWrappers;
       }
-
       //Create Mail instance from data and get JSON body for request
-      const mail = Mail.create(data);
+      const mail = Mail.create(args);
       const body = mail.toJSON();
-
+      
       //Filters the Mail body to avoid sensitive content leakage
       this.filterSecrets(body);
 

packages/mail/src/classes/mail-service.spec.js

@@ -0,0 +1,33 @@
+const { assert } = require('chai');
+
+const MailService = require('./mail-service');
+describe('MailService send', () => {
+  it('should not mutate original data variable', () => {
+    const mailService = new MailService();
+    mailService.setClient({
+      request: (req, cb) => {
+        return new Promise((resolve) => {
+          resolve();
+        });
+      },
+    });
+    const data = {
+      to: '[email protected]',
+      from: '[email protected]', // Use the email address or domain you verified above
+      subject: 'Sending with Twilio SendGrid is Fun',
+      text: 'and easy to do anywhere, even with Node.js',
+      html: '<strong>and easy to do anywhere, even with Node.js</strong>',
+    };
+    return mailService.send(data).then(() => {
+      assert.deepStrictEqual(data,
+        {
+          to: '[email protected]',
+          from: '[email protected]', // Use the email address or domain you verified above
+          subject: 'Sending with Twilio SendGrid is Fun',
+          text: 'and easy to do anywhere, even with Node.js',
+          html: '<strong>and easy to do anywhere, even with Node.js</strong>',
+        });
+
+    });
+  });
+});