Improve taken username warning in registration for when request fails

src/components/views/auth/RegistrationForm.tsx

@@ -44,6 +44,13 @@ enum RegistrationField {
     PasswordConfirm = "field_password_confirm",
 }
 
+enum UsernameAvailableStatus {
+    Unknown,
+    Available,
+    Unavailable,
+    Error,
+}
+
 export const PASSWORD_MIN_SCORE = 3; // safely unguessable: moderate protection from offline slow-hash scenario.
 
 interface IProps {
@@ -348,13 +355,25 @@ export default class RegistrationForm extends React.PureComponent<IProps, IState
         return result;
     };
 
-    private validateUsernameRules = withValidation({
+    private validateUsernameRules = withValidation<this, UsernameAvailableStatus>({
         description: (_, results) => {
             // omit the description if the only failing result is the `available` one as it makes no sense for it.
             if (results.every(({ key, valid }) => key === "available" || valid)) return;
             return _t("Use lowercase letters, numbers, dashes and underscores only");
         },
         hideDescriptionIfValid: true,
+        async deriveData(this: RegistrationForm, { value }) {
+            if (!value) {
+                return UsernameAvailableStatus.Unknown;
+            }
+
+            try {
+                const available = await this.props.matrixClient.isUsernameAvailable(value);
+                return available ? UsernameAvailableStatus.Available : UsernameAvailableStatus.Unavailable;
+            } catch (err) {
+                return UsernameAvailableStatus.Error;
+            }
+        },
         rules: [
             {
                 key: "required",
@@ -369,19 +388,16 @@ export default class RegistrationForm extends React.PureComponent<IProps, IState
             {
                 key: "available",
                 final: true,
-                test: async ({ value }) => {
+                test: async ({ value }, usernameAvailable) => {
                     if (!value) {
                         return true;
                     }
 
-                    try {
-                        await this.props.matrixClient.isUsernameAvailable(value);
-                        return true;
-                    } catch (err) {
-                        return false;
-                    }
+                    return usernameAvailable === UsernameAvailableStatus.Available;
                 },
-                invalid: () => _t("Someone already has that username. Try another or if it is you, sign in below."),
+                invalid: (usernameAvailable) => usernameAvailable === UsernameAvailableStatus.Error
+                    ? _t("Unable to check if username has been taken. Try again later.")
+                    : _t("Someone already has that username. Try another or if it is you, sign in below."),
             },
         ],
     });

src/components/views/elements/Validation.tsx

@@ -92,7 +92,7 @@ export default function withValidation<T = undefined, D = void>({
         }
 
         const data = { value, allowEmpty };
-        const derivedData = deriveData ? await deriveData(data) : undefined;
+        const derivedData: D | undefined = deriveData ? await deriveData.call(this, data) : undefined;
 
         const results: IResult[] = [];
         let valid = true;
@@ -106,13 +106,13 @@ export default function withValidation<T = undefined, D = void>({
                     continue;
                 }
 
-                if (rule.skip && rule.skip.call(this, data, derivedData)) {
+                if (rule.skip?.call(this, data, derivedData)) {
                     continue;
                 }
 
                 // We're setting `this` to whichever component holds the validation
                 // function. That allows rules to access the state of the component.
-                const ruleValid = await rule.test.call(this, data, derivedData);
+                const ruleValid: boolean = await rule.test.call(this, data, derivedData);
                 valid = valid && ruleValid;
                 if (ruleValid && rule.valid) {
                     // If the rule's result is valid and has text to show for

src/i18n/strings/en_EN.json

@@ -2941,6 +2941,7 @@
     "Other users can invite you to rooms using your contact details": "Other users can invite you to rooms using your contact details",
     "Enter phone number (required on this homeserver)": "Enter phone number (required on this homeserver)",
     "Use lowercase letters, numbers, dashes and underscores only": "Use lowercase letters, numbers, dashes and underscores only",
+    "Unable to check if username has been taken. Try again later.": "Unable to check if username has been taken. Try again later.",
     "Someone already has that username. Try another or if it is you, sign in below.": "Someone already has that username. Try another or if it is you, sign in below.",
     "Phone (optional)": "Phone (optional)",
     "Register": "Register",