From 78bb1d5c542a3ffd94055c41f72a20463167383f Mon Sep 17 00:00:00 2001
From: Michael Telatynski <7t3chguy@gmail.com>
Date: Fri, 2 Sep 2022 11:12:28 +0100
Subject: [PATCH 1/3] Handle M_INVALID_USERNAME on /register/available

---
 src/components/views/auth/RegistrationForm.tsx | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/components/views/auth/RegistrationForm.tsx b/src/components/views/auth/RegistrationForm.tsx
index 690acd5c318..6607dfecd5e 100644
--- a/src/components/views/auth/RegistrationForm.tsx
+++ b/src/components/views/auth/RegistrationForm.tsx
@@ -48,6 +48,7 @@ enum UsernameAvailableStatus {
     Available,
     Unavailable,
     Error,
+    Invalid,
 }
 
 export const PASSWORD_MIN_SCORE = 3; // safely unguessable: moderate protection from offline slow-hash scenario.
@@ -363,7 +364,9 @@ export default class RegistrationForm extends React.PureComponent<IProps, IState
                 const available = await this.props.matrixClient.isUsernameAvailable(value);
                 return available ? UsernameAvailableStatus.Available : UsernameAvailableStatus.Unavailable;
             } catch (err) {
-                return UsernameAvailableStatus.Error;
+                return err.errcode === "M_INVALID_USERNAME"
+                    ? UsernameAvailableStatus.Invalid
+                    : UsernameAvailableStatus.Error;
             }
         },
         rules: [
@@ -374,7 +377,8 @@ export default class RegistrationForm extends React.PureComponent<IProps, IState
             },
             {
                 key: "safeLocalpart",
-                test: ({ value }) => !value || SAFE_LOCALPART_REGEX.test(value),
+                test: ({ value }, usernameAvailable) => (!value || SAFE_LOCALPART_REGEX.test(value))
+                    && usernameAvailable !== UsernameAvailableStatus.Invalid,
                 invalid: () => _t("Some characters not allowed"),
             },
             {

From 0f82c9c8281c7cd892f2a84f52f0ea6f27ea414e Mon Sep 17 00:00:00 2001
From: Michael Telatynski <7t3chguy@gmail.com>
Date: Wed, 7 Sep 2022 15:28:48 +0100
Subject: [PATCH 2/3] Add tests

---
 cypress/e2e/register/register.spec.ts | 44 +++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/cypress/e2e/register/register.spec.ts b/cypress/e2e/register/register.spec.ts
index 8d1076f0b78..a0c120414d2 100644
--- a/cypress/e2e/register/register.spec.ts
+++ b/cypress/e2e/register/register.spec.ts
@@ -85,4 +85,48 @@ describe("Registration", () => {
         cy.get(".mx_DevicesPanel_myDevice .mx_DevicesPanel_deviceTrust .mx_E2EIcon")
             .should("have.class", "mx_E2EIcon_verified");
     });
+
+    it("should require username to fulfil requirements and be available", () => {
+        cy.get(".mx_ServerPicker_change", { timeout: 15000 }).click();
+        cy.get(".mx_ServerPickerDialog_continue").should("be.visible");
+        cy.get(".mx_ServerPickerDialog_otherHomeserver").type(synapse.baseUrl);
+        cy.get(".mx_ServerPickerDialog_continue").click();
+        // wait for the dialog to go away
+        cy.get('.mx_ServerPickerDialog').should('not.exist');
+
+        cy.get("#mx_RegistrationForm_username").should("be.visible");
+
+        cy.intercept("**/_matrix/client/*/register/available?username=_alice", {
+            statusCode: 400,
+            headers: {
+                "Content-Type": "application/json",
+            },
+            body: {
+                errcode: "M_INVALID_USERNAME",
+                error: "User ID may not begin with _",
+            },
+        });
+        cy.get("#mx_RegistrationForm_username").type("_alice");
+        cy.get(".mx_Field_tooltip")
+            .should("have.class", "mx_Tooltip_visible")
+            .should("contain.text", "Some characters not allowed");
+
+        cy.intercept("**/_matrix/client/*/register/available?username=bob", {
+            statusCode: 400,
+            headers: {
+                "Content-Type": "application/json",
+            },
+            body: {
+                errcode: "M_USER_IN_USE",
+                error: "The desired username is already taken",
+            },
+        });
+        cy.get("#mx_RegistrationForm_username").type("{selectAll}{backspace}bob");
+        cy.get(".mx_Field_tooltip")
+            .should("have.class", "mx_Tooltip_visible")
+            .should("contain.text", "Someone already has that username");
+
+        cy.get("#mx_RegistrationForm_username").type("{selectAll}{backspace}foobar");
+        cy.get(".mx_Field_tooltip").should("not.have.class", "mx_Tooltip_visible");
+    });
 });

From cd90f118f34be01a8495e7cd489dd2b7131fd339 Mon Sep 17 00:00:00 2001
From: Michael Telatynski <7t3chguy@gmail.com>
Date: Wed, 7 Sep 2022 15:31:10 +0100
Subject: [PATCH 3/3] Make typescript check happier

---
 src/components/views/auth/RegistrationForm.tsx | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/components/views/auth/RegistrationForm.tsx b/src/components/views/auth/RegistrationForm.tsx
index 6607dfecd5e..d1f7c9acc45 100644
--- a/src/components/views/auth/RegistrationForm.tsx
+++ b/src/components/views/auth/RegistrationForm.tsx
@@ -18,6 +18,7 @@ limitations under the License.
 import React from 'react';
 import { MatrixClient } from 'matrix-js-sdk/src/client';
 import { logger } from "matrix-js-sdk/src/logger";
+import { MatrixError } from 'matrix-js-sdk/src/matrix';
 
 import * as Email from '../../../email';
 import { looksValid as phoneNumberLooksValid } from '../../../phonenumber';
@@ -364,9 +365,10 @@ export default class RegistrationForm extends React.PureComponent<IProps, IState
                 const available = await this.props.matrixClient.isUsernameAvailable(value);
                 return available ? UsernameAvailableStatus.Available : UsernameAvailableStatus.Unavailable;
             } catch (err) {
-                return err.errcode === "M_INVALID_USERNAME"
-                    ? UsernameAvailableStatus.Invalid
-                    : UsernameAvailableStatus.Error;
+                if (err instanceof MatrixError && err.errcode === "M_INVALID_USERNAME") {
+                    return UsernameAvailableStatus.Invalid;
+                }
+                return UsernameAvailableStatus.Error;
             }
         },
         rules: [