AccountCache: Rename get to getEvenIfMissing

AccountCache#get returns an empty AccountState to represent a missing
account, but most callers are not aware of this. Make this behavior
obvious by having an explicit name.

Most callers of AccountCache should use maybeGet and handle the missing
account case explicitly. A follow-up change can now rename maybeGet to
get to make it more obvious that this is the method that should be used
by default.

Within this series quite some callers of AccountCache#get have been
migrated to AccountCache#maybeGet. The remaining usages of
AccountCache#get (now AccountCache#getEvenIfMissing) cannot easily be
migrated to AccountCache#maybeGet, at least not without changing
behavior. Ideally we still want to migrate all callers to
AccountCache#maybeGet and then get rid of AccountCache#get (now
AccountCache#getEvenIfMissing), but this work is left for future
changes.

Change-Id: Ib993cb5ce9498ed52032ce9f7be0d314456ff20d
Signed-off-by: Edwin Kempin <ekempin@google.com>

java/com/google/gerrit/server/IdentifiedUser.java

@@ -277,9 +277,28 @@ public class IdentifiedUser extends CurrentUser {
     return true;
   }
 
+  /**
+   * Returns the account state of the identified user.
+   *
+   * @return the account state of the identified user, an empty account state if the account is
+   *     missing
+   */
   public AccountState state() {
     if (state == null) {
-      state = accountCache.get(getAccountId());
+      // TODO(ekempin):
+      // Ideally we would only create IdentifiedUser instances for existing accounts. To ensure
+      // this we could load the account state eagerly on the creation of IdentifiedUser and fail is
+      // the account is missing. In most cases, e.g. when creating an IdentifiedUser for a request
+      // context, we really want to fail early if the account is missing. However there are some
+      // usages where an IdentifiedUser may be instantiated for a missing account. We may go
+      // through all of them and ensure that they never try to create an IdentifiedUser for a
+      // missing account or make this explicit by adding a createEvenIfMissing method to
+      // IdentifiedUser.GenericFactory. However since this is a lot of effort we stick with calling
+      // AccountCache#getEvenIfMissing(Account.Id) for now.
+      // Alternatively we could be could also return an Optional<AccountState> from the state()
+      // method and let callers handle the missing account case explicitly. But this would be a lot
+      // of work too.
+      state = accountCache.getEvenIfMissing(getAccountId());
     }
     return state;
   }
@@ -310,6 +329,11 @@ public class IdentifiedUser extends CurrentUser {
             () -> firstNonNull(getAccount().getPreferredEmail(), "a/" + getAccountId().get()));
   }
 
+  /**
+   * Returns the account of the identified user.
+   *
+   * @return the account of the identified user, an empty account if the account is missing
+   */
   public Account getAccount() {
     return state().getAccount();
   }