Add feature for automatically serialize fields tagged as "*,json"

This commit implements the features, but it still needs tests
to confirm it is working.

json.go

@@ -0,0 +1,30 @@
+package kissorm
+
+import (
+	"database/sql/driver"
+	"encoding/json"
+	"fmt"
+)
+
+// This type was created to make it easier to adapt
+// input attributes to be convertible to and from JSON
+// before sending or receiving it from the database.
+type jsonSerializable struct {
+	Attr interface{}
+}
+
+// Scan Implements the Scanner interface in order to load
+// this field from the JSON stored in the database
+func (j *jsonSerializable) Scan(value interface{}) error {
+	rawJSON, ok := value.([]byte)
+	if !ok {
+		return fmt.Errorf("unexpected type received to Scan: %T", value)
+	}
+	return json.Unmarshal(rawJSON, j.Attr)
+}
+
+// Value Implements the Valuer interface in order to save
+// this field as JSON on the database.
+func (j jsonSerializable) Value() (driver.Value, error) {
+	return json.Marshal(j.Attr)
+}

kiss_orm.go

@@ -554,6 +554,12 @@ func buildInsertQuery(
 		return "", nil, err
 	}
 
+	t := reflect.TypeOf(record)
+	if t.Kind() == reflect.Ptr {
+		t = t.Elem()
+	}
+	info := structs.GetTagInfo(t)
+
 	for _, fieldName := range idFieldNames {
 		// Remove any ID field that was not set:
 		if reflect.ValueOf(recordMap[fieldName]).IsZero() {
@@ -569,7 +575,12 @@ func buildInsertQuery(
 	params = make([]interface{}, len(recordMap))
 	valuesQuery := make([]string, len(recordMap))
 	for i, col := range columnNames {
-		params[i] = recordMap[col]
+		recordValue := recordMap[col]
+		params[i] = recordValue
+		if info.ByName(col).SerializeAsJSON {
+			params[i] = jsonSerializable{Attr: recordValue}
+		}
+
 		valuesQuery[i] = dialect.Placeholder(i)
 	}
 
@@ -724,7 +735,7 @@ func parseInputFunc(fn interface{}) (reflect.Type, error) {
 
 type nopScanner struct{}
 
-var nopScannerValue = reflect.ValueOf(&nopScanner{})
+var nopScannerValue = reflect.ValueOf(&nopScanner{}).Interface()
 
 func (nopScanner) Scan(value interface{}) error {
 	return nil
@@ -757,10 +768,13 @@ func scanRows(rows *sql.Rows, record interface{}) error {
 
 		valueScanner := nopScannerValue
 		if fieldInfo.Valid {
-			valueScanner = v.Field(fieldInfo.Index).Addr()
+			valueScanner = v.Field(fieldInfo.Index).Addr().Interface()
+			if fieldInfo.SerializeAsJSON {
+				valueScanner = jsonSerializable{Attr: valueScanner}
+			}
 		}
 
-		scanArgs = append(scanArgs, valueScanner.Interface())
+		scanArgs = append(scanArgs, valueScanner)
 	}
 
 	return rows.Scan(scanArgs...)

structs/structs.go

@@ -3,6 +3,7 @@ package structs
 import (
 	"fmt"
 	"reflect"
+	"strings"
 
 	"github.com/pkg/errors"
 )
@@ -16,6 +17,7 @@ type fieldInfo struct {
 	Name            string
 	Index           int
 	Valid           bool
+	SerializeAsJSON bool
 }
 
 func (s structInfo) ByIndex(idx int) *fieldInfo {
@@ -296,9 +298,17 @@ func getTagNames(t reflect.Type) structInfo {
 			continue
 		}
 
+		tags := strings.Split(name, ",")
+		serializeAsJSON := false
+		if len(tags) > 1 {
+			name = tags[0]
+			serializeAsJSON = tags[1] == "json"
+		}
+
 		info.Add(fieldInfo{
 			Name:            name,
 			Index:           i,
+			SerializeAsJSON: serializeAsJSON,
 		})
 	}