Add presicion property into expression question fix #6556 (#6582)

* Add presicion property into expression question fix #6556

* Add description

---------

Co-authored-by: Roman Tsukanov <roman.tsukanov@devexpress.com>

src/question_expression.ts

@@ -74,7 +74,7 @@ export class QuestionExpressionModel extends Question {
       this.expressionRunner = new ExpressionRunner(this.expression);
     }
     this.expressionRunner.onRunComplete = (newValue) => {
-      this.value = newValue;
+      this.value = this.roundValue(newValue);
       this.unlocCalculation();
     };
     this.expressionRunner.run(values, properties);
@@ -91,6 +91,7 @@ export class QuestionExpressionModel extends Question {
    * Default value: -1
    * @see displayStyle
    * @see minimumFractionDigits
+   * @see precision
    */
   public get maximumFractionDigits(): number {
     return this.getPropertyValue("maximumFractionDigits");
@@ -195,6 +196,23 @@ export class QuestionExpressionModel extends Question {
   public set useGrouping(val: boolean) {
     this.setPropertyValue("useGrouping", val);
   }
+  /**
+   * Specifies how many decimal digits to keep in the expression value.
+   *
+   * Default value: -1 (unlimited)
+   * @see maximumFractionDigits
+   */
+  public get precision(): number {
+    return this.getPropertyValue("precision");
+  }
+  public set precision(val: number) {
+    this.setPropertyValue("precision", val);
+  }
+  private roundValue(val: any): any {
+    if(this.precision < 0) return val;
+    if(!Helpers.isNumber(val)) return val;
+    return parseFloat(val.toFixed(this.precision));
+  }
   protected getValueAsStr(val: any): string {
     if (this.displayStyle == "date") {
       var d = new Date(val);
@@ -423,6 +441,7 @@ Serializer.addClass(
     { name: "maximumFractionDigits:number", default: -1 },
     { name: "minimumFractionDigits:number", default: -1 },
     { name: "useGrouping:boolean", default: true },
+    { name: "precision:number", default: -1, category: "data" },
     { name: "enableIf", visible: false },
     { name: "isRequired", visible: false },
     { name: "readOnly", visible: false },

tests/question_expressiontests.ts

@@ -172,3 +172,25 @@ QUnit.test("setting data doesn't calculate expressions survey.questionsOnPageMod
   assert.equal(question.displayValue, "3", "display value is correct");
   assert.equal(question.formatedValue, "3", "formatedValue is correct");
 });
+QUnit.test("round to digits", function (assert) {
+  const survey = new SurveyModel({
+    questions: [
+      { "name": "q1", "type": "expression", "expression": "1111/125" },
+      { "name": "q2", "type": "expression", "expression": "1111/125", "precision": 2 },
+      { "name": "q3", "type": "expression", "expression": "1111/125", "precision": 1 },
+      { "name": "q4", "type": "expression", "expression": "1111/125", "precision": 0 }
+    ]
+  });
+  const q1 = <QuestionExpressionModel>survey.getQuestionByName("q1");
+  const q2 = <QuestionExpressionModel>survey.getQuestionByName("q2");
+  const q3 = <QuestionExpressionModel>survey.getQuestionByName("q3");
+  const q4 = <QuestionExpressionModel>survey.getQuestionByName("q4");
+  assert.equal(q1.precision, -1, "precision:-1");
+  assert.equal(q2.precision, 2, "precision:2");
+  assert.equal(q3.precision, 1, "precision:1");
+  assert.equal(q4.precision, 0, "precision:0");
+  assert.equal(q1.value, 8.888, "precision - default (-1)");
+  assert.equal(q2.value, 8.89, "precision - 2");
+  assert.equal(q3.value, 8.9, "precision - 1");
+  assert.equal(q4.value, 9, "precision - 0");
+});