Add comparable errors for target_session_attrs.

fbconn/config.go

@@ -675,6 +675,19 @@ func makeConnectTimeoutDialFunc(timeout time.Duration) DialFunc {
 	return d.DialContext
 }
 
+var (
+	// ErrReadOnlyConnection is returned when a read-write connection is required but the connection is read-only.
+	ErrReadOnlyConnection = errors.New("read only connection")
+	// ErrReadWriteConnection is returned when a read-only connection is required but the connection is read-write.
+	ErrReadWriteConnection = errors.New("connection is not read only")
+	// ErrPrimary is returned when a replica connection is required but the connection is primary.
+	ErrPrimary = errors.New("not replica")
+	// ErrReplica is returned when a primary connection is required but the connection is replica.
+	ErrReplica = errors.New("not primary")
+	// ErrReplicationNotConfigured is returned when replication not configured on host.
+	ErrReplicationNotConfigured = errors.New("replication is not configured")
+)
+
 // ValidateConnectTargetSessionAttrsReadWrite is a ValidateConnectFunc that implements libpq compatible
 // target_session_attrs=read-write.
 func ValidateConnectTargetSessionAttrsReadWrite(ctx context.Context, fbConn *FbConn) error {
@@ -684,7 +697,7 @@ func ValidateConnectTargetSessionAttrsReadWrite(ctx context.Context, fbConn *FbC
 	}
 
 	if res.Rows[0][0][3] == 1 {
-		return errors.New("read only connection")
+		return ErrReadOnlyConnection
 	}
 
 	return nil
@@ -699,7 +712,7 @@ func ValidateConnectTargetSessionAttrsReadOnly(ctx context.Context, fbConn *FbCo
 	}
 
 	if res.Rows[0][0][3] != 1 {
-		return errors.New("connection is not read only")
+		return ErrReadWriteConnection
 	}
 
 	return nil
@@ -717,7 +730,7 @@ func checkSessionAttrIsPrimary(ctx context.Context, fbConn *FbConn) (bool, error
 		return false, nil
 	}
 
-	return false, errors.New("replication is not configured")
+	return false, ErrReplicationNotConfigured
 }
 
 // ValidateConnectTargetSessionAttrsReplica is a [ValidateConnectFunc] that implements
@@ -730,7 +743,7 @@ func ValidateConnectTargetSessionAttrsReplica(ctx context.Context, fbConn *FbCon
 	}
 
 	if isPrimary {
-		return errors.New("not replica")
+		return ErrPrimary
 	}
 
 	return nil
@@ -746,7 +759,7 @@ func ValidateConnectTargetSessionAttrsPrimary(ctx context.Context, fbConn *FbCon
 	}
 
 	if !isPrimary {
-		return errors.New("not primary")
+		return ErrReplica
 	}
 
 	return nil
@@ -762,7 +775,7 @@ func ValidateConnectTargetSessionAttrsPreferReplica(ctx context.Context, fbConn
 	}
 
 	if isPrimary {
-		return &NotPreferredError{err: errors.New("not replica")}
+		return &NotPreferredError{err: ErrPrimary}
 	}
 
 	return nil

fbconn/errors_internal_test.go

@@ -3,8 +3,11 @@ package fbconn
 import (
 	"context"
 	"errors"
+	"os"
 	"testing"
+	"time"
 
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
@@ -21,3 +24,47 @@ func TestSyncConnClosedConnErrorIsErrConnClosed(t *testing.T) {
 	require.Error(t, err)
 	require.ErrorIs(t, err, ErrConnClosed)
 }
+
+func TestConnectWithValidateConnectSessionAttributeErrors(t *testing.T) {
+	tests := []struct {
+		name string
+		err  error
+		msg  string
+	}{
+		{"read-only connection", ErrReadOnlyConnection, "read only connection"},
+		{"read-write connection", ErrReadWriteConnection, "connection is not read only"},
+		{"primary", ErrPrimary, "not replica"},
+		{"replica", ErrReplica, "not primary"},
+		{"replication not configured", ErrReplicationNotConfigured, "replication is not configured"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			ctx, cancel := context.WithTimeout(context.Background(), 120*time.Second)
+			defer cancel()
+
+			config, err := ParseConfig(os.Getenv("FBX_TEST_DATABASE"))
+			require.NoError(t, err)
+			config.ValidateConnect = func(context.Context, *FbConn) error {
+				return tt.err
+			}
+
+			conn, err := ConnectConfig(ctx, config)
+			if !assert.NotNil(t, err) {
+				_ = conn.Close(ctx)
+			}
+			require.ErrorIs(t, err, tt.err)
+			var connectErr *ConnectError
+			require.ErrorAs(t, err, &connectErr)
+			require.ErrorContains(t, err, "ValidateConnect failed: "+tt.msg)
+			require.EqualError(t, tt.err, tt.msg)
+		})
+	}
+
+	t.Run("prefer-replica", func(t *testing.T) {
+		err := &NotPreferredError{err: ErrPrimary}
+		require.ErrorIs(t, err, ErrPrimary)
+		require.NotErrorIs(t, err, ErrReplica)
+		require.EqualError(t, err, "standby server not found: not replica")
+	})
+}

fbconn/fbconn_test.go

@@ -420,6 +420,26 @@ func TestConnectWithValidateConnectTargetSessionAttrsReadWrite(t *testing.T) {
 	if !assert.NotNil(t, err) {
 		_ = conn.Close(ctx)
 	}
+	require.ErrorIs(t, err, fbconn.ErrReadOnlyConnection)
+}
+
+func TestConnectWithValidateConnectTargetSessionAttrsReadOnly(t *testing.T) {
+	t.Parallel()
+
+	ctx, cancel := context.WithTimeout(context.Background(), 120*time.Second)
+	defer cancel()
+
+	config, err := fbconn.ParseConfig(os.Getenv("FBX_TEST_DATABASE"))
+	require.NoError(t, err)
+
+	config.ValidateConnect = fbconn.ValidateConnectTargetSessionAttrsReadOnly
+	config.DefaultTransactionReadOnly = false
+
+	conn, err := fbconn.ConnectConfig(ctx, config)
+	if !assert.NotNil(t, err) {
+		_ = conn.Close(ctx)
+	}
+	require.ErrorIs(t, err, fbconn.ErrReadWriteConnection)
 }
 
 func TestConnectWithAfterConnect(t *testing.T) {