Checkboxes/TagBox with Select All and None - Survey results contains …

…an unexpected blank/empty string fix #7657 (#7664)

src/question_checkbox.ts

@@ -512,9 +512,11 @@ export class QuestionCheckboxModel extends QuestionCheckboxBase {
     var res = [];
     var visItems = this.visibleChoices;
     for (var i = 0; i < visItems.length; i++) {
+      const item = visItems[i];
+      if(item === this.selectAllItem) continue;
       var val = visItems[i].value;
       if (Helpers.isTwoValueEquals(val, this.invisibleOldValues[val])) {
-        if (!this.isItemSelected(visItems[i])) {
+        if (!this.isItemSelected(item)) {
           res.push(val);
         }
         delete this.invisibleOldValues[val];

tests/question_baseselecttests.ts

@@ -1632,3 +1632,29 @@ QUnit.test("checkbox max(min)SelectedChoices validation", (assert) => {
   q.maxSelectedChoices = 5;
   assert.equal(q.maxSelectedChoices, 5, "q.maxSelectedChoices, #5");
 });
+QUnit.test("checkbox, selectAll & survey.data, bug#7657", (assert) => {
+  const survey = new SurveyModel({
+    "elements": [
+      {
+        "type": "checkbox",
+        "name": "q1",
+        "isRequired": true,
+        "choices": [
+          "One",
+          "Two",
+          "Three"
+        ],
+        "showNoneItem": true,
+        "showSelectAllItem": true
+      }
+    ]
+  });
+  const q = <QuestionCheckboxModel>survey.getQuestionByName("q1");
+  q.selectAll();
+  q.clickItemHandler(q.choices[2]);
+  assert.deepEqual(q.value, ["One", "Two"], "q.value, #1");
+  assert.deepEqual(survey.data, { q1: ["One", "Two"] }, "survey.data, #1");
+  survey.doComplete();
+  assert.deepEqual(q.value, ["One", "Two"], "q.value, #2");
+  assert.deepEqual(survey.data, { q1: ["One", "Two"] }, "survey.data, #2");
+});