JSON fields for saving collection diff

tpl/macros_struct.twig

@@ -257,6 +257,42 @@ func Save{{ ctx.s.name }}CollectionDiff(ctx context.Context, dbe metadb.Execer,
 		{% endfor %}
 		{% endif %}
 
+		{% if has_token(ctx.s, 'table_json_kv') %}
+		var jsonBuilder strings.Builder
+
+		jsonValues := make([]any, 0, {{ ctx.json_fields|length }})
+		{% for f in ctx.json_fields %}
+		{% set fname = f|fname %}
+		if rec.{{ f|fname }}Changed() {
+			{%~ if f.type is builtin %}
+			jsonBuilder.WriteString(",'$.{{ f|alias }}',?")
+			jsonValues = append(jsonValues, rec.{{ f|fname }})
+			{%~ else %}
+			jsonBuilder.WriteString(",'$.{{ f|alias }}',")
+			jsonBytes, err := json.Marshal(rec.{{ fname }})
+			if err != nil {
+				return errors.WithStack(err)
+			}
+			jsonBuilder.WriteString("CAST(")
+			jsonBuilder.WriteString(strconv.Quote(string(jsonBytes)))
+			jsonBuilder.WriteString(" AS JSON)")
+			{%~ endif %}
+		}
+		{% endfor %}
+
+		if jsonBuilder.Len() > 0 {
+			builder.query.WriteString(",`kv`")
+			builder.values.WriteString(",?")
+
+			builder.update.WriteString(",`kv`=JSON_SET(`kv`")
+			builder.update.WriteString(jsonBuilder.String())
+			builder.update.WriteRune(')')
+
+			builder.rawValues = append(builder.rawValues, rec.{{ ctx.s.name }}JsonValues)
+			builder.rawValues = append(builder.rawValues, jsonValues...)
+		}
+		{% endif %}
+
 		builder.values.WriteRune(')')
 		builder.values.WriteRune(',')
 	}