session: fix and test some return values

GetGroupID is given a session ID as a param and so should return
ErrSessionNotFound if that session is not found. GetSessionIDs is given
a groupID as a param and so should return ErrUnknownGroup if that group
does not exist.

This commit updates the kvstore and sql implementations to return the
correct error values and also ensures that this is properly tested now.

Author: ellemouton

session/kvdb_store.go

@@ -637,7 +637,7 @@ func (db *BoltStore) GetGroupID(_ context.Context, sessionID ID) (ID, error) {
 		sessionIDBkt := idIndex.Bucket(sessionID[:])
 		if sessionIDBkt == nil {
 			return fmt.Errorf("%w: no index entry for session "+
-				"ID: %x", ErrUnknownGroup, sessionID)
+				"ID: %x", ErrSessionNotFound, sessionID)
 		}
 
 		groupIDBytes := sessionIDBkt.Get(groupIDKey)
@@ -696,7 +696,7 @@ func getSessionIDs(sessionBkt *bbolt.Bucket, groupID ID) ([]ID, error) {
 
 	groupIDBkt := groupIndexBkt.Bucket(groupID[:])
 	if groupIDBkt == nil {
-		return nil, fmt.Errorf("no sessions for group ID %v",
+		return nil, fmt.Errorf("%w: group ID %v", ErrUnknownGroup,
 			groupID)
 	}
 

session/sql_store.go

@@ -593,7 +593,7 @@ func (s *SQLStore) GetGroupID(ctx context.Context, sessionID ID) (ID, error) {
 		// Get the session using the legacy Alias.
 		sess, err := db.GetSessionByAlias(ctx, sessionID[:])
 		if errors.Is(err, sql.ErrNoRows) {
-			return ErrUnknownGroup
+			return ErrSessionNotFound
 		} else if err != nil {
 			return err
 		}

session/store_test.go

@@ -32,6 +32,14 @@ func TestBasicSessionStore(t *testing.T) {
 	_, err := db.GetSession(ctx, ID{1, 3, 4, 4})
 	require.ErrorIs(t, err, ErrSessionNotFound)
 
+	// Do the same for other "Get" type methods to assert that the correct
+	// errors are returned.
+	_, err = db.GetGroupID(ctx, ID{1, 2, 3, 4})
+	require.ErrorIs(t, err, ErrSessionNotFound)
+
+	_, err = db.GetSessionIDs(ctx, ID{1, 2, 3, 4})
+	require.ErrorIs(t, err, ErrUnknownGroup)
+
 	// Reserve a session. This should succeed.
 	s1, err := reserveSession(db, "session 1")
 	require.NoError(t, err)
@@ -182,7 +190,7 @@ func TestBasicSessionStore(t *testing.T) {
 	require.Empty(t, sessions)
 
 	_, err = db.GetGroupID(ctx, s4.ID)
-	require.ErrorIs(t, err, ErrUnknownGroup)
+	require.ErrorIs(t, err, ErrSessionNotFound)
 
 	// Only session 1 should remain in this group.
 	sessIDs, err = db.GetSessionIDs(ctx, s4.GroupID)