work for the surveyjs/private-tasks#242

src/question_checkbox.ts

@@ -10,6 +10,8 @@ import { surveyLocalization } from "./surveyStrings";
 import { LocalizableString } from "./localizablestring";
 import { CssClassBuilder } from "./utils/cssClassBuilder";
 import { IQuestion } from "./base-interfaces";
+import { SurveyError } from "./survey-error";
+import { CustomError } from "./error";
 
 /**
  * A class that describes the Checkbox question type.
@@ -182,6 +184,20 @@ export class QuestionCheckboxModel extends QuestionCheckboxBase {
     this.setPropertyValue("maxSelectedChoices", val);
     this.filterItems();
   }
+  /**
+   * Sets a limit on the number of selected choices.
+   *
+   * Default value: 0 (unlimited)
+   *
+   * > This property only limits the number of choice items that can be selected by users. You can select any number of choice items in code, regardless of the `maxSelectedChoices` value.
+   */
+  public get minSelectedChoices(): number {
+    return this.getPropertyValue("minSelectedChoices");
+  }
+  public set minSelectedChoices(val: number) {
+    if (val < 0) val = 0;
+    this.setPropertyValue("minSelectedChoices", val);
+  }
   /**
    * An array of selected choice items. Includes the "Other" and "None" choice items if they are selected, but not "Select All". Items are sorted in the order they were selected.
    * @see visibleChoices
@@ -215,6 +231,23 @@ export class QuestionCheckboxModel extends QuestionCheckboxBase {
     const val = this.renderedValue as Array<any>;
     return val.map((item: any) => new ItemValue(item));
   }
+
+  protected onCheckForErrors(
+    errors: Array<SurveyError>,
+    isOnValueChanged: boolean
+  ) {
+    super.onCheckForErrors(errors, isOnValueChanged);
+    if (isOnValueChanged) return;
+
+    if (this.minSelectedChoices > 0 && this.checkMinSelectedChoicesUnreached()) {
+      const minError = new CustomError(
+        this.getLocalizationFormatString("minSelectError", this.minSelectedChoices),
+        this
+      );
+      errors.push(minError);
+    }
+  }
+
   protected onEnableItemCallBack(item: ItemValue): boolean {
     if (!this.shouldCheckMaxSelectedChoices()) return true;
     return this.isItemSelected(item);
@@ -242,6 +275,14 @@ export class QuestionCheckboxModel extends QuestionCheckboxBase {
     var len = !Array.isArray(val) ? 0 : val.length;
     return len >= this.maxSelectedChoices;
   }
+
+  private checkMinSelectedChoicesUnreached(): boolean {
+    if (this.minSelectedChoices < 1) return false;
+    var val = this.value;
+    var len = !Array.isArray(val) ? 0 : val.length;
+    return len < this.minSelectedChoices;
+  }
+
   protected getItemClassCore(item: any, options: any) {
     const __dummy_value = this.value; //trigger dependencies from koValue for knockout
     options.isSelectAllItem = item === this.selectAllItem;
@@ -439,6 +480,7 @@ export class QuestionCheckboxModel extends QuestionCheckboxBase {
       json["type"] = "radiogroup";
     }
     json["maxSelectedChoices"] = 0;
+    json["minSelectedChoices"] = 0;
     return json;
   }
   public isAnswerCorrect(): boolean {
@@ -537,6 +579,7 @@ Serializer.addClass(
     { name: "showSelectAllItem:boolean", alternativeName: "hasSelectAll" },
     { name: "separateSpecialChoices", visible: true },
     { name: "maxSelectedChoices:number", default: 0 },
+    { name: "minSelectedChoices:number", default: 0 },
     {
       name: "selectAllText",
       serializationProperty: "locSelectAllText",

src/question_ranking.ts

@@ -547,6 +547,7 @@ Serializer.addClass(
     { name: "selectAllText", visible: false, isSerializable: false },
     { name: "colCount:number", visible: false, isSerializable: false },
     { name: "maxSelectedChoices", visible: false, isSerializable: false },
+    { name: "minSelectedChoices", visible: false, isSerializable: false },
     { name: "separateSpecialChoices", visible: false, isSerializable: false },
     {
       name: "longTap",

src/question_text.ts

@@ -2,7 +2,7 @@ import { QuestionFactory } from "./questionfactory";
 import { Serializer } from "./jsonobject";
 import { LocalizableString, LocalizableStrings } from "./localizablestring";
 import { Helpers, HashTable } from "./helpers";
-import { EmailValidator, SurveyValidator } from "./validator";
+import { EmailValidator } from "./validator";
 import { SurveyError } from "./survey-error";
 import { CustomError } from "./error";
 import { settings } from "./settings";
@@ -71,16 +71,7 @@ export class QuestionTextModel extends QuestionTextBase {
       this.setRenderedMinMax(values, properties);
     }
   }
-  public getValidators(): Array<SurveyValidator> {
-    var validators = super.getValidators();
-    if (
-      this.inputType === "email" &&
-      !this.validators.some((v) => v.getType() === "emailvalidator")
-    ) {
-      validators.push(new EmailValidator());
-    }
-    return validators;
-  }
+
   isLayoutTypeSupported(layoutType: string): boolean {
     return true;
   }
@@ -257,7 +248,22 @@ export class QuestionTextModel extends QuestionTextBase {
       ); };
       errors.push(maxError);
     }
+
+    var name = this.name;
+    var emailValidator = new EmailValidator();
+    if (
+      this.inputType === "email" &&
+      !this.validators.some((v) => v.getType() === "emailvalidator") &&
+      emailValidator.validate(this.value, name)
+    ) {
+      const maxError = new CustomError(
+        emailValidator.getErrorText(name),
+        this
+      );
+      errors.push(maxError);
+    }
   }
+
   protected canSetValueToSurvey(): boolean {
     if (!this.isMinMaxType) return true;
     const isValid = !this.isValueLessMin && !this.isValueGreaterMax;

src/validator.ts

@@ -38,7 +38,7 @@ export class SurveyValidator extends Base {
   get locText(): LocalizableString {
     return this.getLocalizableString("text");
   }
-  protected getErrorText(name: string): string {
+  public getErrorText(name: string): string {
     if (this.text) return this.text;
     return this.getDefaultErrorText(name);
   }

tests/surveyquestiontests.ts

@@ -5116,6 +5116,29 @@ QUnit.test("select items and then set maxSelectedChoices in checkbox", function
   assert.equal(question.otherItem.isEnabled, false, "otherItem is disabled");
 });
 
+QUnit.test("select items and then set minSelectedChoices in checkbox", function (assert) {
+  var survey = new SurveyModel({
+    elements: [
+      {
+        type: "checkbox",
+        name: "q1",
+        choices: [1, 2, 3, 4, 5],
+        hasSelectAll: true,
+        hasOther: true,
+      },
+    ],
+  });
+  var question = <QuestionCheckboxModel>survey.getQuestionByName("q1");
+  question.minSelectedChoices = 3;
+  question.value = [2, 3];
+  question.validate();
+  assert.equal(question.hasErrors(), true, "has errors");
+
+  question.value = [2, 3, 4];
+  question.validate();
+  assert.equal(question.hasErrors(), false, "has no errors");
+});
+
 QUnit.test("Matrix Question: columns with true/false values", function (assert) {
   var matrix = new QuestionMatrixModel("q1");
   matrix.columns = [true, false, 0, "0", 1];