Index: SpecialUserlogin.php
===================================================================
--- SpecialUserlogin.php	(revision 67921)
+++ SpecialUserlogin.php	(working copy)
@@ -234,6 +234,13 @@
 			return false;
 		}
 
+		// Patch for MediaWikiAuth extension
+		if ( $this->checkImportableUser( $this->mName ) ) {
+			$this->mainLoginForm( wfMsg( 'userexists' ) );
+			return false;
+		}
+		// Patch ends here
+
 		// If we are not allowing users to login locally, we should be checking
 		// to see if the user is actually able to authenticate to the authenti-
 		// cation server before they create an account (otherwise, they can
@@ -594,8 +601,15 @@
 				wfDebug( __METHOD__.": user does not exist\n" );
 				return self::NOT_EXISTS;
 			}
-			if ( !$wgAuth->authenticate( $user->getName(), $this->mPassword ) ) {
+			// Patch for MediaWikiAuth extension
+			$errormsg = null;
+			if ( !$wgAuth->authenticate( $user->getName(), $this->mPassword, $errormsg ) ) {
 				wfDebug( __METHOD__.": \$wgAuth->authenticate() returned false, aborting\n" );
+
+				# The AuthPlugin may have set a custom error message
+				$this->mainLoginForm( isset( $errormsg ) ? $errormsg : wfMsg( 'wrongpassword' ) );
+				// Patch ends here
+
 				return self::WRONG_PLUGIN_PASS;
 			}
 		}
@@ -647,7 +661,7 @@
 				$this->mainLoginForm( wfMsg( 'noname' ) );
 				break;
 			case self::WRONG_PLUGIN_PASS:
-				$this->mainLoginForm( wfMsg( 'wrongpassword' ) );
+				# Message is handled in the authentication code
 				break;
 			case self::NOT_EXISTS:
 				if( $wgUser->isAllowed( 'createaccount' ) ){
@@ -688,6 +702,51 @@
 	}
 
 	/**
+	 * New function for MediaWikiAuth extension
+	 *
+	 * @param $username Mixed: username to check
+	 * @return Boolean
+	 */
+	private function checkImportableUser( $username ) {
+		# Check against a table of existing names to import
+		$dbr = wfGetDB( DB_SLAVE );
+
+		# If this table exists, there's users to import
+		if ( $dbr->tableExists( 'user' ) ) {
+			$res = $dbr->select(
+				'user',
+				array( 'user_id' ),
+				array( 'user_name' => $username ),
+				__METHOD__
+			);
+			$row = $dbr->fetchObject( $res );
+			if ( $row ) {
+				$dbr->freeResult( $res );
+				return true;
+			}
+			$dbr->freeResult( $res );
+
+			# Because some people have ' in their usernames
+			$username = $dbr->strencode( $username );
+
+			# Let's see if the count of revisions by their name is greater than 1
+			# This is not 100% correct as it is possible to have a username
+			# like greenReaper, enter greenreaper, and match
+			# However, we're just checking to see if we should even try, here
+			$revisions = $dbr->selectField(
+				'revision',
+				'COUNT(1)',
+				'rev_user_text = \'' . $username . '\'',
+				__METHOD__
+			);
+			if ( $revisions ) {
+				return true;
+			}
+		}
+		return false;
+	}
+
+	/**
 	 * @private
 	 */
 	function mailPassword() {
@@ -746,7 +805,14 @@
 			return;
 		}
 		if ( 0 == $u->getID() ) {
-			$this->mainLoginForm( wfMsgWikiHtml( 'nosuchuser', htmlspecialchars( $u->getName() ) ) );
+			// Patch for MediaWikiAuth extension
+			# Try and get this to work for users that might be imported
+			if ( $this->checkImportableUser( $u->getName() ) ) {
+				$this->mainLoginForm( wfMsg( 'mwa-must-be-imported' ) );
+			} else {
+				$this->mainLoginForm( wfMsgWikiHtml( 'nosuchuser', htmlspecialchars( $u->getName() ) ) );
+			}
+			// Patch ends here
 			return;
 		}