Handle and i18n M_THREEPID_IN_USE during registration (#6986)

Author: t3chguy

src/components/structures/auth/Registration.tsx

@@ -272,7 +272,7 @@ export default class Registration extends React.Component<IProps, IState> {
 
     private onUIAuthFinished = async (success: boolean, response: any) => {
         if (!success) {
-            let msg = response.message || response.toString();
+            let errorText = response.message || response.toString();
             // can we give a better error message?
             if (response.errcode === 'M_RESOURCE_LIMIT_EXCEEDED') {
                 const errorTop = messageForResourceLimitError(
@@ -291,7 +291,7 @@ export default class Registration extends React.Component<IProps, IState> {
                         '': _td("Please <a>contact your service administrator</a> to continue using this service."),
                     },
                 );
-                msg = <div>
+                errorText = <div>
                     <p>{ errorTop }</p>
                     <p>{ errorDetail }</p>
                 </div>;
@@ -301,15 +301,18 @@ export default class Registration extends React.Component<IProps, IState> {
                     msisdnAvailable = msisdnAvailable || flow.stages.includes('m.login.msisdn');
                 }
                 if (!msisdnAvailable) {
-                    msg = _t('This server does not support authentication with a phone number.');
+                    errorText = _t('This server does not support authentication with a phone number.');
                 }
             } else if (response.errcode === "M_USER_IN_USE") {
-                msg = _t("That username already exists, please try another.");
+                errorText = _t("That username already exists, please try another.");
+            } else if (response.errcode === "M_THREEPID_IN_USE") {
+                errorText = _t("That e-mail address is already in use.");
             }
+
             this.setState({
                 busy: false,
                 doingUIAuth: false,
-                errorText: msg,
+                errorText,
             });
             return;
         }

src/i18n/strings/en_EN.json

@@ -3056,6 +3056,7 @@
     "Registration has been disabled on this homeserver.": "Registration has been disabled on this homeserver.",
     "This server does not support authentication with a phone number.": "This server does not support authentication with a phone number.",
     "That username already exists, please try another.": "That username already exists, please try another.",
+    "That e-mail address is already in use.": "That e-mail address is already in use.",
     "Continue with %(ssoButtons)s": "Continue with %(ssoButtons)s",
     "%(ssoButtons)s Or %(usernamePassword)s": "%(ssoButtons)s Or %(usernamePassword)s",
     "Already have an account? <a>Sign in here</a>": "Already have an account? <a>Sign in here</a>",