Allow changing servers on nonfatal errors

[dbkr]

@turt2live: hopefully this is a sensible way to do this

Fixes element-hq/element-web#10016

[turt2live]

this works, however so does:

try {
  await AutoDiscoveryUtils.validateServerConfigWithStaticUrls(hsUrl, isUrl);
} catch (e) {
  if (AutoDiscoveryUtils.isLivelinessError(e)) {
    // Continue anyways logic
  }
  // else E_BROKEN
}

lgtm either way. Would be nice to have 1 less blank line on line 121 though.

[dbkr]

I thought we needed the return value from validateServerConfigWithStaticUrls to continue here though? Which we don't get if it throws.

[turt2live]

we do, but we can always call it again with syntaxOnly=true.

[dbkr]

In this case we need to do so immediately though because we need to pass it to this.props.onServerConfigChange? I guess actually this is equivalent to just specifying syntaxOnly in the first place though?

[dbkr]

oh - it's not equivalent because nonfatal error !== liveness check fail (ie. we still want to fail if the HS isn't reachable)

[turt2live]

ah, yes, it would be... so just a try/catch around a syntaxOnly call and you should be fine

[turt2live]

hmm... if non-fatal is != to liveliness then the code you have here is fine, because syntaxOnly=true disables liveliness

[dbkr]

ok yeah, I think this is right then, ie. it will let you continue with the change if the IS server is down but not if the HS is down.