chore: import upstream snapshot with attribution

server/cast/json.go

@@ -0,0 +1,54 @@
+// Copyright 2024 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 cast
+
+import (
+	"github.com/cockroachdb/errors"
+	"github.com/dolthub/go-mysql-server/sql"
+
+	"github.com/dolthub/doltgresql/core/casts"
+	"github.com/dolthub/doltgresql/core/id"
+	"github.com/dolthub/doltgresql/server/functions/framework"
+	pgtypes "github.com/dolthub/doltgresql/server/types"
+)
+
+// initJson handles all casts that are built-in. This comprises only the source types.
+func initJson(builtInCasts map[id.Cast]casts.Cast) {
+	jsonAssignment(builtInCasts)
+}
+
+// jsonAssignment registers all assignment casts. This comprises only the source types.
+func jsonAssignment(builtInCasts map[id.Cast]casts.Cast) {
+	framework.MustAddAssignmentTypeCast(builtInCasts, framework.TypeCast{
+		FromType: pgtypes.Json,
+		ToType:   pgtypes.JsonB,
+		Function: func(ctx *sql.Context, val any, _, targetType *pgtypes.DoltgresType) (any, error) {
+			switch v := val.(type) {
+			case sql.StringWrapper:
+				result, err := v.Unwrap(ctx)
+				if err != nil {
+					return nil, err
+				}
+				return targetType.IoInput(ctx, result)
+			case string:
+				return targetType.IoInput(ctx, v)
+			case sql.JSONWrapper:
+				return v, nil
+			default:
+				return nil, errors.Errorf("unexpected JSON value type: %T", val)
+			}
+		},
+	})
+}