chore: import upstream snapshot with attribution

server/functions/array_to_string.go

@@ -0,0 +1,83 @@
+// 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 functions
+
+import (
+	"strings"
+
+	"github.com/cockroachdb/errors"
+	"github.com/dolthub/go-mysql-server/sql"
+
+	"github.com/dolthub/doltgresql/server/functions/framework"
+	pgtypes "github.com/dolthub/doltgresql/server/types"
+)
+
+// initArrayToString registers the functions to the catalog.
+func initArrayToString() {
+	framework.RegisterFunction(array_to_string_anyarray_text)
+	framework.RegisterFunction(array_to_string_anyarray_text_text)
+}
+
+// array_to_string_anyarray_text represents the PostgreSQL array function taking 2 parameters.
+var array_to_string_anyarray_text = framework.Function2{
+	Name:               "array_to_string",
+	Return:             pgtypes.Text,
+	Parameters:         [2]*pgtypes.DoltgresType{pgtypes.AnyArray, pgtypes.Text},
+	IsNonDeterministic: true,
+	Strict:             true,
+	Callable: func(ctx *sql.Context, paramsAndReturn [3]*pgtypes.DoltgresType, val1, val2 any) (any, error) {
+		arr := val1.([]any)
+		delimiter := val2.(string)
+		return getStringArrFromAnyArray(ctx, paramsAndReturn[0], arr, delimiter, nil)
+	},
+}
+
+// array_to_string_anyarray_text_text represents the PostgreSQL array function taking 3 parameter.
+var array_to_string_anyarray_text_text = framework.Function3{
+	Name:               "array_to_string",
+	Return:             pgtypes.Text,
+	Parameters:         [3]*pgtypes.DoltgresType{pgtypes.AnyArray, pgtypes.Text, pgtypes.Text},
+	IsNonDeterministic: true,
+	Strict:             false,
+	Callable: func(ctx *sql.Context, paramsAndReturn [4]*pgtypes.DoltgresType, val1, val2, val3 any) (any, error) {
+		if val1 == nil {
+			return nil, errors.Errorf("could not determine polymorphic type because input has type unknown")
+		} else if val2 == nil {
+			return nil, nil
+		}
+		arr := val1.([]any)
+		delimiter := val2.(string)
+		return getStringArrFromAnyArray(ctx, paramsAndReturn[0], arr, delimiter, val3)
+	},
+}
+
+// getStringArrFromAnyArray takes inputs of any array, delimiter and null entry replacement. It uses the IoOutput() of the
+// base type of the AnyArray type to get string representation of array elements.
+func getStringArrFromAnyArray(ctx *sql.Context, arrType *pgtypes.DoltgresType, arr []any, delimiter string, nullEntry any) (string, error) {
+	baseType := arrType.ArrayBaseType()
+	strs := make([]string, 0)
+	for _, el := range arr {
+		if el != nil {
+			v, err := baseType.IoOutput(ctx, el)
+			if err != nil {
+				return "", err
+			}
+			strs = append(strs, v)
+		} else if nullEntry != nil {
+			strs = append(strs, nullEntry.(string))
+		}
+	}
+	return strings.Join(strs, delimiter), nil
+}