Scan unknown types into *any as string or []byte based on format code

#2399

Author: jackc

pgtype/pgtype.go

@@ -1135,10 +1135,18 @@ func (m *Map) planScan(oid uint32, formatCode int16, target any, depth int) Scan
 		}
 	}
 
-	if dt != nil {
-		if _, ok := target.(*any); ok {
-			return &pointerEmptyInterfaceScanPlan{codec: dt.Codec, m: m, oid: oid, formatCode: formatCode}
+	if _, ok := target.(*any); ok {
+		var codec Codec
+		if dt != nil {
+			codec = dt.Codec
+		} else {
+			if formatCode == TextFormatCode {
+				codec = TextCodec{}
+			} else {
+				codec = ByteaCodec{}
+			}
 		}
+		return &pointerEmptyInterfaceScanPlan{codec: codec, m: m, oid: oid, formatCode: formatCode}
 	}
 
 	return &scanPlanFail{m: m, oid: oid, formatCode: formatCode}

pgtype/pgtype_test.go

@@ -165,6 +165,21 @@ func TestMapScanBinaryFormatInterfacePtr(t *testing.T) {
 	assert.Equal(t, "foo", got)
 }
 
+func TestMapScanUnknownOIDToPtrToAny(t *testing.T) {
+	unknownOID := uint32(999999)
+	srcBuf := []byte("foo")
+	m := pgtype.NewMap()
+
+	var a any
+	err := m.Scan(unknownOID, pgx.TextFormatCode, srcBuf, &a)
+	assert.NoError(t, err)
+	assert.Equal(t, "foo", a)
+
+	err = m.Scan(unknownOID, pgx.BinaryFormatCode, srcBuf, &a)
+	assert.NoError(t, err)
+	assert.Equal(t, []byte("foo"), a)
+}
+
 func TestMapScanUnknownOIDToStringsAndBytes(t *testing.T) {
 	unknownOID := uint32(999999)
 	srcBuf := []byte("foo")