Do not fail on server liveliness checks during startup

Also warn about deprecated config option usage.

See #9828

README.md

@@ -113,10 +113,10 @@ For a good example, see https://riot.im/develop/config.json.
    Riot to use. The object is the same as returned by [https://<server_name>/.well-known/matrix/client](https://matrix.org/docs/spec/client_server/latest.html#get-well-known-matrix-client),
    with added support for a `server_name` under the `m.homeserver` section to display
    a custom homeserver name. Alternatively, the config can contain a `default_server_name`
-   instead which is where Riot will go to get that same object - see the `.well-known`
-   link above for more information. Note that the `default_server_name` is used to get
-   a complete server configuration whereas the `server_name` in the `default_server_config`
-   is for display purposes only.
+   instead which is where Riot will go to get that same object, although this option is
+   deprecated - see the `.well-known` link above for more information on using this option. 
+   Note that the `default_server_name` is used to get a complete server configuration 
+   whereas the `server_name` in the `default_server_config` is for display purposes only.
    * *Note*: The URLs can also be individually specified as `default_hs_url` and 
      `default_is_url`, however these are deprecated. They are maintained for backwards
      compatibility with older configurations. `default_is_url` is respected only

src/vector/index.js

@@ -465,6 +465,11 @@ async function verifyServerConfig() {
         // context of email validation. Because we don't respect them otherwise, we do not need
         // to parse or consider them here.
 
+        // Note: Although we throw all 3 possible configuration options through a .well-known-style
+        // verification, we do not care if the servers are online at this point. We do moderately
+        // care if they are syntactically correct though, so we shove them through the .well-known
+        // validators for that purpose.
+
         const config = SdkConfig.get();
         let wkConfig = config['default_server_config']; // overwritten later under some conditions
         const serverName = config['default_server_name'];
@@ -486,6 +491,10 @@ async function verifyServerConfig() {
 
         if (hsUrl) {
             console.log("Config uses a default_hs_url - constructing a default_server_config using this information");
+            console.warn(
+                "DEPRECATED CONFIG OPTION: In the future, default_hs_url will not be accepted. Please use " +
+                "default_server_config instead.",
+            );
 
             wkConfig = {
                 "m.homeserver": {
@@ -507,18 +516,22 @@ async function verifyServerConfig() {
 
         if (serverName) {
             console.log("Config uses a default_server_name - doing .well-known lookup");
+            console.warn(
+                "DEPRECATED CONFIG OPTION: In the future, default_server_name will not be accepted. Please " +
+                "use default_server_config instead.",
+            );
             discoveryResult = await AutoDiscovery.findClientConfig(serverName);
         }
 
-        validatedConfig = AutoDiscoveryUtils.buildValidatedConfigFromDiscovery(serverName, discoveryResult);
+        validatedConfig = AutoDiscoveryUtils.buildValidatedConfigFromDiscovery(serverName, discoveryResult, true);
     } catch (e) {
         const {hsUrl, isUrl, userId} = Lifecycle.getLocalStorageSessionVars();
         if (hsUrl && userId) {
             console.error(e);
             console.warn("A session was found - suppressing config error and using the session's homeserver");
 
             console.log("Using pre-existing hsUrl and isUrl: ", {hsUrl, isUrl});
-            validatedConfig = await AutoDiscoveryUtils.validateServerConfigWithStaticUrls(hsUrl, isUrl);
+            validatedConfig = await AutoDiscoveryUtils.validateServerConfigWithStaticUrls(hsUrl, isUrl, true);
         } else {
             // the user is not logged in, so scream
             throw e;