chore: import upstream snapshot with attribution

server/analyzer/validate_create_schema.go

@@ -0,0 +1,54 @@
+// Copyright 2025 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 analyzer
+
+import (
+	"github.com/dolthub/go-mysql-server/sql"
+	"github.com/dolthub/go-mysql-server/sql/analyzer"
+	"github.com/dolthub/go-mysql-server/sql/plan"
+	"github.com/dolthub/go-mysql-server/sql/transform"
+
+	"github.com/dolthub/doltgresql/core"
+)
+
+// ValidateCreateSchema validates that CREATE SCHEMA is executed with a valid database context.
+// In PostgreSQL, schemas exist within databases, so CREATE SCHEMA requires an active database.
+// See: https://github.com/dolthub/doltgresql/issues/1863
+func ValidateCreateSchema(
+	ctx *sql.Context,
+	a *analyzer.Analyzer,
+	n sql.Node,
+	scope *plan.Scope,
+	sel analyzer.RuleSelector,
+	qFlags *sql.QueryFlags,
+) (sql.Node, transform.TreeIdentity, error) {
+	cs, ok := n.(*plan.CreateSchema)
+	if !ok {
+		return n, transform.SameTree, nil
+	}
+
+	// Check if the current database actually has a working root.
+	// GetRootFromContext will return sql.ErrDatabaseNotFound if the database
+	// is not properly initialized.
+	_, _, err := core.GetRootFromContext(ctx)
+	if err != nil {
+		if sql.ErrDatabaseNotFound.Is(err) {
+			return nil, transform.SameTree, sql.ErrNoDatabaseSelected.New()
+		}
+		return nil, transform.SameTree, err
+	}
+
+	return cs, transform.SameTree, nil
+}