add lax field to namedStructRowScanner

rows.go

@@ -565,8 +565,28 @@ func RowToAddrOfStructByName[T any](row CollectableRow) (*T, error) {
 	return &value, err
 }
 
+// RowToStructByNameLax returns a T scanned from row. T must be a struct. T must have greater than or equal number of named public
+// fields as row has fields. The row and T fields will by matched by name. The match is case-insensitive. The database
+// column name can be overridden with a "db" struct tag. If the "db" struct tag is "-" then the field will be ignored.
+func RowToStructByNameLax[T any](row CollectableRow) (T, error) {
+	var value T
+	err := row.Scan(&namedStructRowScanner{ptrToStruct: &value, lax: true})
+	return value, err
+}
+
+// RowToAddrOfStructByNameLax returns the address of a T scanned from row. T must be a struct. T must have greater than or
+// equal number of named public fields as row has fields. The row and T fields will by matched by name. The match is
+// case-insensitive. The database column name can be overridden with a "db" struct tag. If the "db" struct tag is "-"
+// then the field will be ignored.
+func RowToAddrOfStructByNameLax[T any](row CollectableRow) (*T, error) {
+	var value T
+	err := row.Scan(&namedStructRowScanner{ptrToStruct: &value, lax: true})
+	return &value, err
+}
+
 type namedStructRowScanner struct {
 	ptrToStruct any
+	lax         bool
 }
 
 func (rs *namedStructRowScanner) ScanRow(rows Rows) error {
@@ -637,7 +657,13 @@ func (rs *namedStructRowScanner) appendScanTargets(dstElemValue reflect.Value, s
 				colName = sf.Name
 			}
 			fpos := fieldPosByName(fldDescs, colName)
-			if fpos == -1 || fpos >= len(scanTargets) {
+			if fpos == -1 {
+				if rs.lax {
+					continue
+				}
+				return nil, fmt.Errorf("cannot find field %s in returned row", colName)
+			}
+			if fpos >= len(scanTargets) && !rs.lax {
 				return nil, fmt.Errorf("cannot find field %s in returned row", colName)
 			}
 			scanTargets[fpos] = dstElemValue.Field(i).Addr().Interface()
@@ -646,92 +672,3 @@ func (rs *namedStructRowScanner) appendScanTargets(dstElemValue reflect.Value, s
 
 	return scanTargets, err
 }
-
-// RowToStructByNameLax returns a T scanned from row. T must be a struct. T must have greater than or equal number of named public
-// fields as row has fields. The row and T fields will by matched by name. The match is case-insensitive. The database
-// column name can be overridden with a "db" struct tag. If the "db" struct tag is "-" then the field will be ignored.
-func RowToStructByNameLax[T any](row CollectableRow) (T, error) {
-	var value T
-	err := row.Scan(&namedStructRowLaxScanner{ptrToStruct: &value})
-	return value, err
-}
-
-// RowToAddrOfStructByNameLax returns the address of a T scanned from row. T must be a struct. T must have greater than or
-// equal number of named public fields as row has fields. The row and T fields will by matched by name. The match is
-// case-insensitive. The database column name can be overridden with a "db" struct tag. If the "db" struct tag is "-"
-// then the field will be ignored.
-func RowToAddrOfStructByNameLax[T any](row CollectableRow) (*T, error) {
-	var value T
-	err := row.Scan(&namedStructRowLaxScanner{ptrToStruct: &value})
-	return &value, err
-}
-
-type namedStructRowLaxScanner struct {
-	ptrToStruct any
-}
-
-func (rs *namedStructRowLaxScanner) ScanRow(rows Rows) error {
-	dst := rs.ptrToStruct
-	dstValue := reflect.ValueOf(dst)
-	if dstValue.Kind() != reflect.Ptr {
-		return fmt.Errorf("dst not a pointer")
-	}
-
-	dstElemValue := dstValue.Elem()
-	scanTargets, err := rs.appendScanTargets(dstElemValue, nil, rows.FieldDescriptions())
-	if err != nil {
-		return err
-	}
-
-	for i, t := range scanTargets {
-		if t == nil {
-			return fmt.Errorf("struct doesn't have corresponding row field %s", rows.FieldDescriptions()[i].Name)
-		}
-	}
-
-	return rows.Scan(scanTargets...)
-}
-
-func (rs *namedStructRowLaxScanner) appendScanTargets(dstElemValue reflect.Value, scanTargets []any, fldDescs []pgconn.FieldDescription) ([]any, error) {
-	var err error
-	dstElemType := dstElemValue.Type()
-
-	if scanTargets == nil {
-		scanTargets = make([]any, len(fldDescs))
-	}
-
-	for i := 0; i < dstElemType.NumField(); i++ {
-		sf := dstElemType.Field(i)
-		if sf.PkgPath != "" && !sf.Anonymous {
-			// Field is unexported, skip it.
-			continue
-		}
-		// Handle anoymous struct embedding, but do not try to handle embedded pointers.
-		if sf.Anonymous && sf.Type.Kind() == reflect.Struct {
-			scanTargets, err = rs.appendScanTargets(dstElemValue.Field(i), scanTargets, fldDescs)
-			if err != nil {
-				return nil, err
-			}
-		} else {
-			dbTag, dbTagPresent := sf.Tag.Lookup(structTagKey)
-			if dbTagPresent {
-				dbTag = strings.Split(dbTag, ",")[0]
-			}
-			if dbTag == "-" {
-				// Field is ignored, skip it.
-				continue
-			}
-			colName := dbTag
-			if !dbTagPresent {
-				colName = sf.Name
-			}
-			fpos := fieldPosByName(fldDescs, colName)
-			if fpos == -1 {
-				continue
-			}
-			scanTargets[fpos] = dstElemValue.Field(i).Addr().Interface()
-		}
-	}
-
-	return scanTargets, err
-}