According to the documentation it is possible to pass a
login_hint to the OAuth 2 login endpoint (which is the community URL in this case) as long as the
prompt is also passed, set to "login":
IMPORTANT To pass the login_hint parameter for Communities, also pass the prompt=login parameter. Together, these parameters redirect the user to the login page with the correct login hint.
However, this doesn't seem to be working for me. I have tried this with both ARC (the Advanced REST Client chrome app) and by manually constructing the OAuth 2 URL of the form:
https://the-community-host.force.com/the-community-url-path?response_type=token& client_id=3MVxxxxxxxxxxTheOAuthConnectedAppClientIdxxxxxxxxx& redirect_uri=https://the-agreed-callback/url& scope=api& [email protected]& prompt=login
(NB: I've also tried URL encoding the "@" in the username but this makes no difference.)
Both approaches result in the login page like:
Note how the URL only includes
ec=302 (one presumes this is indicating a 302 redirect is required to the endpoint callback) and
startURL=%2Fthe-community-url-path%2Fs%2F which seems to cover where the access should eventually end up (the community home page).
Do you know how to get a standard Community login page to include the login_hint as a pre-entered username?