Add common utility for checking 3pid invites

We just need to make sure they are structurally sound - actual validation is done by other parties.

src/RoomInvite.js

@@ -65,6 +65,24 @@ export function showRoomInviteDialog(roomId) {
     });
 }
 
+/**
+ * Checks if the given MatrixEvent is a valid 3rd party user invite.
+ * @param {MatrixEvent} event The event to check
+ * @returns {boolean} True if valid, false otherwise
+ */
+export function isValid3pidInvite(event) {
+    if (!event || event.getType() !== "m.room.third_party_invite") return false;
+
+    // any events without these keys are not valid 3pid invites, so we ignore them
+    const requiredKeys = ['key_validity_url', 'public_key', 'display_name'];
+    for (let i = 0; i < requiredKeys.length; ++i) {
+        if (!event.getContent()[requiredKeys[i]]) return false;
+    }
+
+    // Valid enough by our standards
+    return true;
+}
+
 function _onStartChatFinished(shouldInvite, addrs) {
     if (!shouldInvite) return;
 

src/TextForEvent.js

@@ -17,6 +17,7 @@ import MatrixClientPeg from './MatrixClientPeg';
 import CallHandler from './CallHandler';
 import { _t } from './languageHandler';
 import * as Roles from './Roles';
+import {isValid3pidInvite} from "./RoomInvite";
 
 function textForMemberEvent(ev) {
     // XXX: SYJS-16 "sender is sometimes null for join messages"
@@ -367,7 +368,7 @@ function textForCallInviteEvent(event) {
 function textForThreePidInviteEvent(event) {
     const senderName = event.sender ? event.sender.name : event.getSender();
 
-    if (!event.getContent().display_name) {
+    if (!isValid3pidInvite(event)) {
         const targetDisplayName = event.getPrevContent().display_name || _t("Someone");
         return _t('%(senderName)s revoked the invitation for %(targetDisplayName)s to join the room.', {
             senderName,

src/components/views/rooms/MemberList.js

@@ -20,6 +20,7 @@ import React from 'react';
 import { _t } from '../../../languageHandler';
 import SdkConfig from '../../../SdkConfig';
 import dis from '../../../dispatcher';
+import {isValid3pidInvite} from "../../../RoomInvite";
 const MatrixClientPeg = require("../../../MatrixClientPeg");
 const sdk = require('../../../index');
 const rate_limited_func = require('../../../ratelimitedfunc');
@@ -379,11 +380,7 @@ module.exports = React.createClass({
 
         if (room) {
             return room.currentState.getStateEvents("m.room.third_party_invite").filter(function(e) {
-                // any events without these keys are not valid 3pid invites, so we ignore them
-                const requiredKeys = ['key_validity_url', 'public_key', 'display_name'];
-                for (let i = 0; i < requiredKeys.length; ++i) {
-                    if (e.getContent()[requiredKeys[i]] === undefined) return false;
-                }
+                if (!isValid3pidInvite(e)) return false;
 
                 // discard all invites which have a m.room.member event since we've
                 // already added them.

src/components/views/rooms/ThirdPartyMemberInfo.js

@@ -22,6 +22,7 @@ import {_t} from "../../../languageHandler";
 import dis from "../../../dispatcher";
 import sdk from "../../../index";
 import Modal from "../../../Modal";
+import {isValid3pidInvite} from "../../../RoomInvite";
 
 export default class ThirdPartyMemberInfo extends React.Component {
     static propTypes = {
@@ -64,7 +65,7 @@ export default class ThirdPartyMemberInfo extends React.Component {
     onRoomStateEvents = (ev) => {
         if (ev.getType() === "m.room.third_party_invite" && ev.getStateKey() === this.state.stateKey) {
             const newDisplayName = ev.getContent().display_name;
-            const isInvited = !!newDisplayName; // display_name indicates a valid invite
+            const isInvited = isValid3pidInvite(ev);
 
             const newState = {invited: isInvited};
             if (newDisplayName) newState['displayName'] = newDisplayName;