Checkboxes Question: Choices selected are not reflected in another fi…

…eld using Default Value Expression Property fix #6886 (#6938)

src/question.ts

@@ -2050,12 +2050,9 @@ export class Question extends SurveyElement<Question>
   protected canSetValueToSurvey(): boolean {
     return true;
   }
-  protected valueFromData(val: any): any {
-    return val;
-  }
-  protected valueToData(val: any): any {
-    return val;
-  }
+  protected valueFromData(val: any): any { return val; }
+  protected valueToData(val: any): any { return val; }
+  protected convertToCorrectValue(val: any): any { return val; }
   protected onValueChanged(): void { }
   protected isMouseDown: boolean;
   onMouseDown(): void {
@@ -2096,6 +2093,7 @@ export class Question extends SurveyElement<Question>
     this.isValueChangedDirectly = true;
   }
   protected setQuestionValue(newValue: any, updateIsAnswered: boolean = true): void {
+    newValue = this.convertToCorrectValue(newValue);
     const isEqual = this.isTwoValueEquals(this.questionValue, newValue);
     if (!isEqual && !this.isChangingViaDefaultValue) {
       this.setValueChangedDirectly();

src/question_comment.ts

@@ -111,6 +111,7 @@ export class QuestionCommentModel extends QuestionTextBase {
     }
     super.setNewValue(newValue);
   }
+  protected getValueSeparator(): string { return "\n"; }
   public get className() {
     return (this.cssClasses ? this.getControlClass() : "panel-comment-root") || undefined;
   }

src/question_expression.ts

@@ -236,6 +236,10 @@ export class QuestionExpressionModel extends Question {
     }
     return val.toString();
   }
+  protected convertToCorrectValue(val: any): any {
+    if(Array.isArray(val)) return val.join(", ");
+    return val;
+  }
 }
 
 export function getCurrecyCodes(): Array<string> {

src/question_textbase.ts

@@ -120,6 +120,11 @@ export class QuestionTextBase extends Question {
     super.setQuestionValue(newValue, updateIsAnswered);
     this.updateRemainingCharacterCounter(newValue);
   }
+  protected convertToCorrectValue(val: any): any {
+    if(Array.isArray(val)) return val.join(this.getValueSeparator());
+    return val;
+  }
+  protected getValueSeparator(): string { return ", "; }
   public disableNativeUndoRedo = false;
   protected checkForUndo(event: KeyboardEvent) {
     if (this.disableNativeUndoRedo && this.isInputTextUpdate && (event.ctrlKey || event.metaKey)) {

tests/surveyquestiontests.ts

@@ -7156,4 +7156,22 @@ QUnit.test("Dynamic error text in expression validator, bug#6790", function (ass
   assert.equal(error.locText.renderedHtml, "80% left.", "Old error text is correct, #2");
   assert.strictEqual(error, q2.errors[0], "Same errors");
   assert.equal(errorTextChangedCounter, 1, "text has been updated");
+});
+QUnit.test("Set array and convert it to a string, bug#6886", function (assert) {
+  const survey = new SurveyModel({
+    elements: [
+      { type: "text", name: "q1" },
+      { type: "comment", name: "q2" },
+      { type: "expression", name: "q3" }
+    ]
+  });
+  const q1 = survey.getQuestionByName("q1");
+  const q2 = survey.getQuestionByName("q2");
+  const q3 = survey.getQuestionByName("q3");
+  q1.value = ["item1", "item2", "item3"];
+  q2.value = ["item1", "item2", "item3"];
+  q3.value = ["item1", "item2", "item3"];
+  assert.equal(q1.value, "item1, item2, item3", "q1");
+  assert.equal(q2.value, "item1\nitem2\nitem3", "q2");
+  assert.equal(q3.value, "item1, item2, item3", "q3");
 });