feat: add min and max fields to relation widget (resolves #5026) (#5238)

packages/netlify-cms-widget-relation/src/RelationControl.js

@@ -5,7 +5,7 @@ import { Async as AsyncSelect } from 'react-select';
 import { find, isEmpty, last, debounce, get, uniqBy } from 'lodash';
 import { List, Map, fromJS } from 'immutable';
 import { reactSelectStyles } from 'netlify-cms-ui-default';
-import { stringTemplate } from 'netlify-cms-lib-widgets';
+import { stringTemplate, validations } from 'netlify-cms-lib-widgets';
 import { FixedSizeList } from 'react-window';
 
 function Option({ index, style, data }) {
@@ -97,6 +97,26 @@ export default class RelationControl extends React.Component {
     setInactiveStyle: PropTypes.func.isRequired,
   };
 
+  isValid = () => {
+    const { field, value, t } = this.props;
+    const min = field.get('min');
+    const max = field.get('max');
+
+    if (!this.isMultiple()) {
+      return { error: false };
+    }
+
+    const error = validations.validateMinMax(
+      t,
+      field.get('label', field.get('name')),
+      value,
+      min,
+      max,
+    );
+
+    return error ? { error } : { error: false };
+  };
+
   shouldComponentUpdate(nextProps) {
     return (
       this.props.value !== nextProps.value ||

packages/netlify-cms-widget-relation/src/__tests__/relation.spec.js

@@ -133,7 +133,6 @@ const numberFieldsHits = [
     },
   },
 ];
-
 class RelationController extends React.Component {
   state = {
     value: this.props.value,

packages/netlify-cms-widget-relation/src/schema.js

@@ -5,6 +5,8 @@ export default {
     search_fields: { type: 'array', minItems: 1, items: { type: 'string' } },
     file: { type: 'string' },
     multiple: { type: 'boolean' },
+    min: { type: 'integer' },
+    max: { type: 'integer' },
     display_fields: { type: 'array', minItems: 1, items: { type: 'string' } },
     options_length: { type: 'integer' },
   },