Fix of #590 - showRequiredError prop is added

Author: AJIXuMuK

docs/documentation/docs/controls/PeoplePicker.md

@@ -61,7 +61,8 @@ The People picker control can be configured with the following properties:
 | personSelectionLimit | number | no | Defines the limit of people that can be selected in the control | 1 |
 | isRequired | boolean | no | Set if the control is required or not | false |
 | disabled | boolean | no | Set if the control is disabled or not | false |
-| errorMessage | string | no | Specify the error message to display | |
+| errorMessage | string | no | Specifies the error message to display if the the control is required and no items selected | |
+| showRequiredError | boolean | no | Specifies if the component should show mandatory field error message because of some changes occured in parent. Use this props (set to `true`), for example, when "Save" button on the form has been clicked | |
 | errorMessageClassName | string | no | applies custom styling to the error message section | |
 | showtooltip | boolean | no | Defines if need a tooltip or not | false |
 | tooltipMessage | string | no | Specify the tooltip message to display | |

src/controls/peoplepicker/IPeoplePicker.ts

@@ -53,6 +53,10 @@ export interface IPeoplePickerProps {
    * Mandatory field error message
    */
   errorMessage?: string;
+  /**
+   * Specifies if the component should show mandatory field error message because of some changes occured in parent
+   */
+  showRequiredError?: boolean;
   /**
    * Method to check value of People Picker text
    */

src/controls/peoplepicker/PeoplePickerComponent.tsx

@@ -63,6 +63,14 @@ export class PeoplePicker extends React.Component<IPeoplePickerProps, IPeoplePic
     }
   }
 
+  public componentWillReceiveProps(nextProps: IPeoplePickerProps) {
+    if (this.props.showRequiredError !== nextProps.showRequiredError && nextProps.showRequiredError) {
+      this.setState({
+        showRequiredError: !this.state.selectedPersons || !this.state.selectedPersons.length
+      });
+    }
+  }
+
 
   /**
    * Get initial persons