regression: valuePrepareFunction is applied to undefined values from …

…the "newRow" row

It is crazy that the "newRow" row is created before the user clicked on the ADD button. This regression was a lot harder to debug that it should be... phew...

projects/angular2-smart-table/src/lib/lib/data-set/cell.ts

@@ -10,8 +10,14 @@ export class Cell {
 
   constructor(protected value: unknown, protected row: Row, protected column: Column) {
     this.cachedValue = this.value;
-    this.cachedPreparedValue = this.getPreparedValue();
-    this.newValue = this.cachedPreparedValue;
+    if (this.row.index >= 0) {
+      this.cachedPreparedValue = this.getPreparedValue();
+      this.newValue = this.cachedPreparedValue;
+    } else {
+      // we must not call the valuePrepareFunction on freshly created rows that do not contain defined data
+      this.cachedPreparedValue = '';
+      this.newValue = '';
+    }
   }
 
   getColumn(): Column {

projects/angular2-smart-table/src/lib/lib/data-set/data-set.ts

@@ -16,7 +16,7 @@ export class DataSet {
   constructor(data: Array<any> = [], protected columnSettings: IColumns) {
     this.createColumns(columnSettings);
     this.setData(data);
-
+    // TODO: fix that the "new row" is always created, even when the table is not even configured to add new rows
     this.createNewRow();
   }
 
@@ -171,6 +171,9 @@ export class DataSet {
   }
 
   createNewRow() {
+    // TODO: the empty object is invalid data in general and is very likely breaking almost every other function
+    //       in particular, custom valuePrepareFunction can explode (see the related hack in the Cell's constructor)
+    //       we should some day fix this by defining a valueCreateFunction that can create a reasonable default object
     this.newRow = new Row(-1, {}, this);
     this.newRow.isInEditing = true;
   }