From e16688ee406992e7ca358308056df8b35840ac9e Mon Sep 17 00:00:00 2001
From: Andrew <andrew.telnov@gmail.com>
Date: Tue, 14 Nov 2023 08:05:04 +0200
Subject: [PATCH] Expression question display defaultValue instead of empty
 string fix #7343 (#7344)

---
 src/question_expression.ts        |  2 +-
 tests/question_expressiontests.ts | 17 +++++++++++++++++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/question_expression.ts b/src/question_expression.ts
index 159f185d1d..68c365f5af 100644
--- a/src/question_expression.ts
+++ b/src/question_expression.ts
@@ -139,7 +139,7 @@ export class QuestionExpressionModel extends Question {
     this.updateFormatedValue();
   }
   protected getDisplayValueCore(keysAsText: boolean, value: any): any {
-    var val = this.isValueEmpty(value) ? this.defaultValue : value;
+    var val = value === undefined || value === null ? this.defaultValue : value;
     var res = "";
     if (!this.isValueEmpty(val)) {
       var str = this.getValueAsStr(val);
diff --git a/tests/question_expressiontests.ts b/tests/question_expressiontests.ts
index 6bb44cf44c..63e9f1f535 100644
--- a/tests/question_expressiontests.ts
+++ b/tests/question_expressiontests.ts
@@ -296,3 +296,20 @@ QUnit.test("Custom function returns object&array, #7050", function (assert) {
   FunctionFactory.Instance.unregister("func1");
   FunctionFactory.Instance.unregister("func2");
 });
+QUnit.test("Default value and setValueExpression", function (assert) {
+  const survey = new SurveyModel({
+    elements: [
+      { type: "expression", name: "q1", setValueExpression: "iif({q2} = 1, 'b', ''", defaultValue: "a" },
+      { type: "text", name: "q2" }
+    ]
+  });
+  const q1 = survey.getQuestionByName("q1");
+  assert.equal(q1.value, "a", "default value is 'a'");
+  assert.equal(q1.formatedValue, "a", "formatedValue, default value is 'a'");
+  survey.setValue("q2", 1);
+  assert.equal(q1.value, "b", "var1 = 1");
+  assert.equal(q1.formatedValue, "b", "formatedValue, var1 = 1");
+  survey.setValue("q2", 2);
+  assert.equal(q1.value, "", "var1 = 2");
+  assert.equal(q1.formatedValue, "", "formatedValue, var1 = 2");
+});