Change the way the memberships are saved in the client API database

src/github.com/matrix-org/dendrite/clientapi/auth/storage/accounts/membership_table.go

@@ -30,6 +30,11 @@ CREATE TABLE IF NOT EXISTS memberships (
     room_id TEXT NOT NULL,
     -- The ID of the join membership event
     event_id TEXT NOT NULL,
+	-- Is the user still in the room? We use a boolean instead of just deleting
+	-- the row to know if the user has been in the room at some point
+	-- If set to false, event_id would be the event ID of the leave/kick/ban
+	-- membership event
+	still_in_room BOOLEAN NOT NULL,
 
     -- A user can only be member of a room once
     PRIMARY KEY (localpart, room_id)
@@ -40,24 +45,26 @@ CREATE UNIQUE INDEX IF NOT EXISTS membership_event_id ON memberships(event_id);
 `
 
 const insertMembershipSQL = `
-	INSERT INTO memberships(localpart, room_id, event_id) VALUES ($1, $2, $3)
-	ON CONFLICT (localpart, room_id) DO UPDATE SET event_id = EXCLUDED.event_id
+	INSERT INTO memberships(localpart, room_id, event_id, still_in_room)
+	VALUES ($1, $2, $3, $4)
+	ON CONFLICT (localpart, room_id) DO
+	UPDATE SET event_id = EXCLUDED.event_id, still_in_room = EXCLUDED.still_in_room
 `
 
 const selectMembershipSQL = "" +
 	"SELECT * from memberships WHERE localpart = $1 AND room_id = $2"
 
 const selectMembershipsByLocalpartSQL = "" +
-	"SELECT room_id, event_id FROM memberships WHERE localpart = $1"
+	"SELECT room_id, event_id FROM memberships WHERE localpart = $1 AND still_in_room = true"
 
 const selectMembershipsByRoomIDSQL = "" +
-	"SELECT localpart, event_id FROM memberships WHERE room_id = $1"
+	"SELECT localpart, event_id FROM memberships WHERE room_id = $1 AND still_in_room = true"
 
 const deleteMembershipsByEventIDsSQL = "" +
 	"DELETE FROM memberships WHERE event_id = ANY($1)"
 
 const updateMembershipByEventIDSQL = "" +
-	"UPDATE memberships SET event_id = $2 WHERE event_id = $1"
+	"UPDATE memberships SET event_id = $2, still_in_room = $3 WHERE event_id = $1"
 
 type membershipStatements struct {
 	deleteMembershipsByEventIDsStmt  *sql.Stmt
@@ -91,8 +98,8 @@ func (s *membershipStatements) prepare(db *sql.DB) (err error) {
 	return
 }
 
-func (s *membershipStatements) insertMembership(localpart string, roomID string, eventID string, txn *sql.Tx) (err error) {
-	_, err = txn.Stmt(s.insertMembershipStmt).Exec(localpart, roomID, eventID)
+func (s *membershipStatements) insertMembership(localpart string, roomID string, eventID string, stillInRoom bool, txn *sql.Tx) (err error) {
+	_, err = txn.Stmt(s.insertMembershipStmt).Exec(localpart, roomID, eventID, stillInRoom)
 	return
 }
 

src/github.com/matrix-org/dendrite/clientapi/auth/storage/accounts/storage.go

@@ -121,11 +121,12 @@ func (d *Database) SetPartitionOffset(topic string, partition int32, offset int6
 }
 
 // SaveMembership saves the user matching a given localpart as a member of a given
-// room. It also stores the ID of the `join` membership event.
+// room. It also stores the ID of the membership event and a flag on whether the user
+// is still in the room.
 // If a membership already exists between the user and the room, or of the
 // insert fails, returns the SQL error
-func (d *Database) SaveMembership(localpart string, roomID string, eventID string, txn *sql.Tx) error {
-	return d.memberships.insertMembership(localpart, roomID, eventID, txn)
+func (d *Database) SaveMembership(localpart string, roomID string, eventID string, stillInRoom bool, txn *sql.Tx) error {
+	return d.memberships.insertMembership(localpart, roomID, eventID, stillInRoom, txn)
 }
 
 // removeMembershipsByEventIDs removes the memberships of which the `join` membership
@@ -135,9 +136,9 @@ func (d *Database) removeMembershipsByEventIDs(eventIDs []string, txn *sql.Tx) e
 	return d.memberships.deleteMembershipsByEventIDs(eventIDs, txn)
 }
 
-// UpdateMemberships adds the "join" membership events included in a given state
-// events array, and removes those which ID is included in a given array of events
-// IDs. All of the process is run in a transaction, which commits only once/if every
+// UpdateMemberships saves the membership events included in a given state events
+// array, and removes those which ID is included in a given array of events IDs.
+// All of the process is run in a transaction, which commits only once/if every
 // insertion and deletion has been successfully processed.
 // Returns a SQL error if there was an issue with any part of the process
 func (d *Database) UpdateMemberships(eventsToAdd []gomatrixserverlib.Event, idsToRemove []string) error {
@@ -179,8 +180,11 @@ func (d *Database) UpdateMembership(oldEventID string, newEventID string) error
 	return d.memberships.updateMembershipByEventID(oldEventID, newEventID)
 }
 
-// newMembership will save a new membership in the database if the given state
-// event is a "join" membership event
+// newMembership will save a new membership in the database, with a flag on whether
+// the user is still in the room. This flag is set to true if the given state
+// event is a "join" membership event and false if the event is a "leave" or "ban"
+// membership. If the event isn't a m.room.member event with one of these three
+// values, does nothing.
 // If the event isn't a "join" membership event, does nothing
 // If an error occurred, returns it
 func (d *Database) newMembership(ev gomatrixserverlib.Event, txn *sql.Tx) error {
@@ -204,7 +208,13 @@ func (d *Database) newMembership(ev gomatrixserverlib.Event, txn *sql.Tx) error
 
 		// Only "join" membership events can be considered as new memberships
 		if membership == "join" {
-			if err := d.SaveMembership(localpart, roomID, eventID, txn); err != nil {
+			if err := d.SaveMembership(localpart, roomID, eventID, true, txn); err != nil {
+				return err
+			}
+		} else if membership == "leave" || membership == "ban" {
+			// If the user left the room, save the new event ID and mark them as
+			// not in the room anymore
+			if err := d.SaveMembership(localpart, roomID, eventID, false, txn); err != nil {
 				return err
 			}
 		}

src/github.com/matrix-org/dendrite/clientapi/readers/memberships.go

@@ -29,9 +29,8 @@ func GetMemberships(
 	req *http.Request, roomID string, accountDB *accounts.Database,
 	queryAPI api.RoomserverQueryAPI,
 ) util.JSONResponse {
-	// TODO: Check if the user is or has been in the room, and respond with
-	// M_FORBIDDEN if not. If the user has been in the room before but isn't
-	// anymore, send the members list as it was before they left.
+	// TODO: If the user has been in the room before but isn't
+	// anymore, only send the members list as it was before they left.
 
 	memberships, err := accountDB.GetMembershipsByRoomID(roomID)
 	if err != nil {