Add CompositeFields type

This adds support for the text format and removes the need for the
ScanRowValue function.

composite.go

@@ -233,6 +233,96 @@ func (cfs *CompositeBinaryScanner) Err() error {
 	return cfs.err
 }
 
+type CompositeTextScanner struct {
+	rp  int
+	src []byte
+
+	fieldBytes []byte
+	err        error
+}
+
+// NewCompositeTextScanner a scanner over a text encoded composite balue.
+func NewCompositeTextScanner(src []byte) (CompositeTextScanner, error) {
+	if len(src) < 2 {
+		return CompositeTextScanner{}, errors.Errorf("Record incomplete %v", src)
+	}
+
+	if src[0] != '(' {
+		return CompositeTextScanner{}, errors.Errorf("composite text format must start with '('")
+	}
+
+	if src[len(src)-1] != ')' {
+		return CompositeTextScanner{}, errors.Errorf("composite text format must end with ')'")
+	}
+
+	return CompositeTextScanner{
+		rp:  1,
+		src: src,
+	}, nil
+}
+
+// Scan advances the scanner to the next field. It returns false after the last field is read or an error occurs. After
+// Scan returns false, the Err method can be called to check if any errors occurred.
+func (cfs *CompositeTextScanner) Scan() bool {
+	if cfs.err != nil {
+		return false
+	}
+
+	if cfs.rp == len(cfs.src) {
+		return false
+	}
+
+	switch cfs.src[cfs.rp] {
+	case ',', ')': // null
+		cfs.rp++
+		cfs.fieldBytes = nil
+		return true
+	case '"': // quoted value
+		cfs.rp++
+		cfs.fieldBytes = make([]byte, 0, 16)
+		for {
+			ch := cfs.src[cfs.rp]
+
+			if ch == '"' {
+				cfs.rp++
+				if cfs.src[cfs.rp] == '"' {
+					cfs.fieldBytes = append(cfs.fieldBytes, '"')
+					cfs.rp++
+				} else {
+					break
+				}
+			} else {
+				cfs.fieldBytes = append(cfs.fieldBytes, ch)
+				cfs.rp++
+			}
+		}
+		cfs.rp++
+		return true
+	default: // unquoted value
+		start := cfs.rp
+		for {
+			ch := cfs.src[cfs.rp]
+			if ch == ',' || ch == ')' {
+				break
+			}
+			cfs.rp++
+		}
+		cfs.fieldBytes = cfs.src[start:cfs.rp]
+		cfs.rp++
+		return true
+	}
+}
+
+// Bytes returns the bytes of the field most recently read by Scan().
+func (cfs *CompositeTextScanner) Bytes() []byte {
+	return cfs.fieldBytes
+}
+
+// Err returns any error encountered by the scanner.
+func (cfs *CompositeTextScanner) Err() error {
+	return cfs.err
+}
+
 // RecordStart adds record header to the buf
 func RecordStart(buf []byte, fieldCount int) []byte {
 	return pgio.AppendUint32(buf, uint32(fieldCount))

composite_fields.go

@@ -0,0 +1,76 @@
+package pgtype
+
+import (
+	errors "golang.org/x/xerrors"
+)
+
+// CompositeFields scans the fields of a composite type into the elements of the CompositeFields value. To scan a
+// nullable value use a *CompositeFields. It will be set to nil in case of null.
+type CompositeFields []interface{}
+
+func (cf CompositeFields) DecodeBinary(ci *ConnInfo, src []byte) error {
+	if len(cf) == 0 {
+		return errors.Errorf("cannot decode into empty CompositeFields")
+	}
+
+	if src == nil {
+		return errors.Errorf("cannot decode unexpected null into CompositeFields")
+	}
+
+	scanner, err := NewCompositeBinaryScanner(src)
+	if err != nil {
+		return err
+	}
+	if len(cf) != scanner.FieldCount() {
+		return errors.Errorf("SQL composite can't be read, field count mismatch. expected %d , found %d", len(cf), scanner.FieldCount())
+	}
+
+	for i := 0; scanner.Scan(); i++ {
+		err := ci.Scan(scanner.OID(), BinaryFormatCode, scanner.Bytes(), cf[i])
+		if err != nil {
+			return err
+		}
+	}
+
+	if scanner.Err() != nil {
+		return scanner.Err()
+	}
+
+	return nil
+}
+
+func (cf CompositeFields) DecodeText(ci *ConnInfo, src []byte) error {
+	if len(cf) == 0 {
+		return errors.Errorf("cannot decode into empty CompositeFields")
+	}
+
+	if src == nil {
+		return errors.Errorf("cannot decode unexpected null into CompositeFields")
+	}
+
+	scanner, err := NewCompositeTextScanner(src)
+	if err != nil {
+		return err
+	}
+
+	fieldCount := 0
+
+	for i := 0; scanner.Scan(); i++ {
+		err := ci.Scan(0, TextFormatCode, scanner.Bytes(), cf[i])
+		if err != nil {
+			return err
+		}
+
+		fieldCount += 1
+	}
+
+	if scanner.Err() != nil {
+		return scanner.Err()
+	}
+
+	if len(cf) != fieldCount {
+		return errors.Errorf("SQL composite can't be read, field count mismatch. expected %d , found %d", len(cf), fieldCount)
+	}
+
+	return nil
+}

composite_fields_test.go

@@ -0,0 +1,126 @@
+package pgtype_test
+
+import (
+	"context"
+	"testing"
+
+	"github.com/jackc/pgtype"
+	"github.com/jackc/pgtype/testutil"
+	"github.com/jackc/pgx/v4"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCompositeFieldsDecode(t *testing.T) {
+	conn := testutil.MustConnectPgx(t)
+	defer testutil.MustCloseContext(t, conn)
+
+	formats := []int16{pgx.TextFormatCode, pgx.BinaryFormatCode}
+
+	// Assorted values
+	{
+		var a int32
+		var b string
+		var c float64
+
+		for _, format := range formats {
+			err := conn.QueryRow(context.Background(), "select row(1,'hi',2.1)", pgx.QueryResultFormats{format}).Scan(
+				pgtype.CompositeFields{&a, &b, &c},
+			)
+			if !assert.NoErrorf(t, err, "Format: %v", format) {
+				continue
+			}
+
+			assert.EqualValuesf(t, 1, a, "Format: %v", format)
+			assert.EqualValuesf(t, "hi", b, "Format: %v", format)
+			assert.EqualValuesf(t, 2.1, c, "Format: %v", format)
+		}
+	}
+
+	// nulls, string "null", and empty string fields
+	{
+		var a pgtype.Text
+		var b string
+		var c pgtype.Text
+		var d string
+		var e pgtype.Text
+
+		for _, format := range formats {
+			err := conn.QueryRow(context.Background(), "select row(null,'null',null,'',null)", pgx.QueryResultFormats{format}).Scan(
+				pgtype.CompositeFields{&a, &b, &c, &d, &e},
+			)
+			if !assert.NoErrorf(t, err, "Format: %v", format) {
+				continue
+			}
+
+			assert.Nilf(t, a.Get(), "Format: %v", format)
+			assert.EqualValuesf(t, "null", b, "Format: %v", format)
+			assert.Nilf(t, c.Get(), "Format: %v", format)
+			assert.EqualValuesf(t, "", d, "Format: %v", format)
+			assert.Nilf(t, e.Get(), "Format: %v", format)
+		}
+	}
+
+	// null record
+	{
+		var a pgtype.Text
+		var b string
+		cf := pgtype.CompositeFields{&a, &b}
+
+		for _, format := range formats {
+			// Cannot scan nil into
+			err := conn.QueryRow(context.Background(), "select null::record", pgx.QueryResultFormats{format}).Scan(
+				cf,
+			)
+			if assert.Errorf(t, err, "Format: %v", format) {
+				continue
+			}
+			assert.NotNilf(t, cf, "Format: %v", format)
+
+			// But can scan nil into *pgtype.CompositeFields
+			err = conn.QueryRow(context.Background(), "select null::record", pgx.QueryResultFormats{format}).Scan(
+				&cf,
+			)
+			if assert.Errorf(t, err, "Format: %v", format) {
+				continue
+			}
+			assert.Nilf(t, cf, "Format: %v", format)
+		}
+	}
+
+	// quotes and special characters
+	{
+		var a, b, c, d string
+
+		for _, format := range formats {
+			err := conn.QueryRow(context.Background(), `select row('"', 'foo bar', 'foo''bar', 'baz)bar')`, pgx.QueryResultFormats{format}).Scan(
+				pgtype.CompositeFields{&a, &b, &c, &d},
+			)
+			if !assert.NoErrorf(t, err, "Format: %v", format) {
+				continue
+			}
+
+			assert.Equalf(t, `"`, a, "Format: %v", format)
+			assert.Equalf(t, `foo bar`, b, "Format: %v", format)
+			assert.Equalf(t, `foo'bar`, c, "Format: %v", format)
+			assert.Equalf(t, `baz)bar`, d, "Format: %v", format)
+		}
+	}
+
+	// arrays
+	{
+		var a []string
+		var b []int64
+
+		for _, format := range formats {
+			err := conn.QueryRow(context.Background(), `select row(array['foo', 'bar', 'baz'], array[1,2,3])`, pgx.QueryResultFormats{format}).Scan(
+				pgtype.CompositeFields{&a, &b},
+			)
+			if !assert.NoErrorf(t, err, "Format: %v", format) {
+				continue
+			}
+
+			assert.EqualValuesf(t, []string{"foo", "bar", "baz"}, a, "Format: %v", format)
+			assert.EqualValuesf(t, []int64{1, 2, 3}, b, "Format: %v", format)
+		}
+	}
+}

convert.go

@@ -433,38 +433,6 @@ func GetAssignToDstType(dst interface{}) (interface{}, bool) {
 	return nil, false
 }
 
-// ScanRowValue decodes ROW()'s and composite type
-// from src argument using provided decoders. Decoders should match
-// order and count of fields of record being decoded.
-//
-// In practice you can pass pgtype.Value types as decoders, as
-// most of them implement BinaryDecoder interface.
-//
-// ScanRowValue takes ownership of src, caller MUST not use it after call
-func ScanRowValue(ci *ConnInfo, src []byte, dst ...interface{}) error {
-	scanner, err := NewCompositeBinaryScanner(src)
-	if err != nil {
-		return err
-	}
-
-	if len(dst) != scanner.FieldCount() {
-		return errors.Errorf("can't scan row value, number of fields don't match: found=%d expected=%d", scanner.FieldCount(), len(dst))
-	}
-
-	for i := 0; scanner.Scan(); i++ {
-		err := ci.Scan(scanner.OID(), BinaryFormatCode, scanner.Bytes(), dst[i])
-		if err != nil {
-			return err
-		}
-	}
-
-	if scanner.Err() != nil {
-		return scanner.Err()
-	}
-
-	return nil
-}
-
 // EncodeRow builds a binary representation of row values (row(), composite types)
 func EncodeRow(ci *ConnInfo, buf []byte, fields ...Value) (newBuf []byte, err error) {
 	fieldBytes := make([]byte, 0, 128)

custom_composite_test.go

@@ -20,7 +20,7 @@ func (dst *MyType) DecodeBinary(ci *pgtype.ConnInfo, src []byte) error {
 		return errors.New("NULL values can't be decoded. Scan into a &*MyType to handle NULLs")
 	}
 
-	if err := pgtype.ScanRowValue(ci, src, &dst.a, &dst.b); err != nil {
+	if err := (pgtype.CompositeFields{&dst.a, &dst.b}).DecodeBinary(ci, src); err != nil {
 		return err
 	}
 

record_test.go

@@ -79,54 +79,6 @@ var recordTests = []struct {
 	},
 }
 
-// row values are binary compatible with records, so we test our helper
-// routines here
-func TestScanRowValue(t *testing.T) {
-	conn := testutil.MustConnectPgx(t)
-	defer testutil.MustCloseContext(t, conn)
-
-	for i := 0; i < len(recordTests); i++ {
-		tt := recordTests[i]
-		psName := fmt.Sprintf("test%d", i)
-		_, err := conn.Prepare(context.Background(), psName, tt.sql)
-		if err != nil {
-			t.Fatal(err)
-		}
-		t.Run(tt.sql, func(t *testing.T) {
-			desc := []interface{}{}
-			for _, f := range tt.expected.Fields {
-				desc = append(desc, f.(pgtype.BinaryDecoder))
-			}
-
-			var raw pgtype.GenericBinary
-
-			if err := conn.QueryRow(context.Background(), psName, pgx.QueryResultFormats{pgx.BinaryFormatCode}).Scan(&raw); err != nil {
-				t.Error(err)
-				return
-			}
-
-			if raw.Status == pgtype.Null {
-				// ScanRowValue deals with complete rows only, NULL values (but NOT null fields)
-				// should be handled by the calling code
-				return
-			}
-
-			if err := pgtype.ScanRowValue(conn.ConnInfo(), raw.Bytes, desc...); err != nil {
-				t.Error(err)
-			}
-
-			// borrow fields from a neighbor test, this makes scan always fail
-			desc = desc[:0]
-			for _, f := range recordTests[(i+1)%len(recordTests)].expected.Fields {
-				desc = append(desc, f.(pgtype.BinaryDecoder))
-			}
-			if err := pgtype.ScanRowValue(conn.ConnInfo(), raw.Bytes, desc...); err == nil {
-				t.Error("Matching scan didn't fail, despite fields not mathching query result")
-			}
-		})
-	}
-}
-
 func TestRecordTranscode(t *testing.T) {
 	conn := testutil.MustConnectPgx(t)
 	defer testutil.MustCloseContext(t, conn)