chore: import upstream snapshot with attribution

server/hook/table_modify_column.go

@@ -0,0 +1,106 @@
+// Copyright 2026 Dolthub, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package hook
+
+import (
+	"github.com/cockroachdb/errors"
+	"github.com/dolthub/dolt/go/libraries/doltcore/doltdb"
+	"github.com/dolthub/go-mysql-server/sql"
+	"github.com/dolthub/go-mysql-server/sql/plan"
+
+	"github.com/dolthub/doltgresql/core"
+	"github.com/dolthub/doltgresql/core/id"
+	pgtypes "github.com/dolthub/doltgresql/server/types"
+)
+
+// beforeTableModifyColumnChange represents what properties of a column changed when a call is made to BeforeTableModifyColumn.
+type beforeTableModifyColumnChange uint8
+
+const (
+	beforeTableModifyColumnChange_None beforeTableModifyColumnChange = iota
+	beforeTableModifyColumnChange_Type
+)
+
+// BeforeTableModifyColumn handles validation that's unique to Doltgres.
+func BeforeTableModifyColumn(ctx *sql.Context, runner sql.StatementRunner, nodeInterface sql.Node) (sql.Node, error) {
+	n, ok := nodeInterface.(*plan.ModifyColumn)
+	if !ok {
+		return nil, errors.Errorf("MODIFY COLUMN pre-hook expected `*plan.ModifyColumn` but received `%T`", nodeInterface)
+	}
+
+	// Figure out what was changed. We know it's not the name because we have a dedicated *RenameColumn node.
+	changed := beforeTableModifyColumnChange_None
+	newColumn := n.NewColumn()
+	for _, col := range n.TargetSchema() {
+		if col.Name == newColumn.Name {
+			if !col.Type.Equals(newColumn.Type) {
+				changed = beforeTableModifyColumnChange_Type
+			}
+		}
+	}
+	if changed == beforeTableModifyColumnChange_None {
+		return n, nil
+	}
+
+	// Grab the table being altered (so we know the schema)
+	doltTable := core.SQLNodeToDoltTable(n.Table)
+	if doltTable == nil {
+		// If this table isn't a Dolt table then we don't have anything to do
+		return n, nil
+	}
+	_, root, err := core.GetRootFromContext(ctx)
+	if err != nil {
+		return n, nil
+	}
+	tableName := doltTable.TableName()
+	tableAsType := id.NewType(tableName.Schema, tableName.Name)
+	allTableNames, err := root.GetAllTableNames(ctx, false)
+	if err != nil {
+		return nil, err
+	}
+
+	for _, otherTableName := range allTableNames {
+		if doltdb.IsSystemTable(otherTableName) {
+			// System tables don't use any table types
+			continue
+		}
+		otherTable, ok, err := root.GetTable(ctx, otherTableName)
+		if err != nil {
+			return nil, err
+		}
+		if !ok {
+			return nil, errors.Errorf("root returned table name `%s` but it could not be found?", otherTableName.String())
+		}
+		otherTableSch, err := otherTable.GetSchema(ctx)
+		if err != nil {
+			return nil, err
+		}
+		for _, otherCol := range otherTableSch.GetAllCols().GetColumns() {
+			colType := otherCol.TypeInfo.ToSqlType()
+			dgtype, ok := colType.(*pgtypes.DoltgresType)
+			if !ok {
+				// If this isn't a Doltgres type, then it can't be a table type so we can ignore it
+				continue
+			}
+			if dgtype.ID != tableAsType {
+				// This column isn't our table type, so we can ignore it
+				continue
+			}
+			return nil, errors.Errorf(`cannot alter table "%s" because column "%s.%s" uses its row type`,
+				tableName.Name, otherTableName.Name, otherCol.Name)
+		}
+	}
+	return n, nil
+}