Auto merge of #1690 - sgrif:sg-read-only-login, r=jtgeibel

Allow existing users to sign in while READ_ONLY_MODE=1

Currently whenever a user signs in we attempt to update their profile
(display name, avatar, email, etc). If we're in read only mode, we can't
do that. However, preventing them from signing in entirely seems
unfortunate.

If we get a read-only error, we will now try to look for an existing
user, returning that user if found (or any errors that occurred loading
it), and continue to return `ReadOnlyMode` if we couldn't find an
existing user.

A user will have to sign out and back in again after maintenance has
completed if they want to update their information. Ideally we'd display
a warning informing them of this fact, but we don't currently have code
in place to support that, and with < 3 hours remaining until maintenance
time, there's not enough time to write it.

I'd also love to add some explicit tests for this, but none of our
existing tests handle GitHub oauth, and again, there's not enough time
for me to figure out what our recordings need to look like for that.

If we're not comfortable shipping this in this imperfect state (no
warning, no tests), then we should just close this, and folks won't be
able to log in during the maintenance period. That's not the end of the
world. However, I've tested this locally to make sure it behaves
properly (with #1689 as well to make sure we display the right error),
so I'd like to ship this to minimize disruption during the DB
maintenance

Author: bors

src/controllers/user/session.rs

@@ -6,6 +6,8 @@ use rand::distributions::Alphanumeric;
 use rand::{thread_rng, Rng};
 
 use crate::models::{NewUser, User};
+use crate::schema::users;
+use crate::util::errors::{CargoError, ReadOnlyMode};
 
 /// Handles the `GET /authorize_url` route.
 ///
@@ -111,16 +113,30 @@ struct GithubUser {
 }
 
 impl GithubUser {
-    fn save_to_database(&self, access_token: &str, conn: &PgConnection) -> QueryResult<User> {
-        Ok(NewUser::new(
+    fn save_to_database(&self, access_token: &str, conn: &PgConnection) -> CargoResult<User> {
+        NewUser::new(
             self.id,
             &self.login,
             self.email.as_ref().map(|s| &s[..]),
             self.name.as_ref().map(|s| &s[..]),
             self.avatar_url.as_ref().map(|s| &s[..]),
             access_token,
         )
-        .create_or_update(conn)?)
+        .create_or_update(conn)
+        .map_err(Into::into)
+        .or_else(|e: Box<dyn CargoError>| {
+            // If we're in read only mode, we can't update their details
+            // just look for an existing user
+            if e.is::<ReadOnlyMode>() {
+                users::table
+                    .filter(users::gh_id.eq(self.id))
+                    .first(conn)
+                    .optional()?
+                    .ok_or(e)
+            } else {
+                Err(e)
+            }
+        })
     }
 }