fix: handle nullish items (#65)

* fix: handle nullish items

* chore: add a type guard

Author: P0lip

src/components/__tests__/Property.spec.tsx

@@ -5,7 +5,7 @@ import { SchemaNodeWithMeta } from '../../types';
 import { Property, Types } from '../shared';
 
 describe('Property component', () => {
-  it('should render Types with propper type and subtype', () => {
+  it('should render Types with proper type and subtype', () => {
     const node: SchemaNodeWithMeta = {
       id: '1',
       type: 'array',
@@ -24,4 +24,20 @@ describe('Property component', () => {
     expect(wrapper.find(Types)).toHaveProp('type', 'array');
     expect(wrapper.find(Types)).toHaveProp('subtype', 'string');
   });
+
+  it('should handle nullish items', () => {
+    const node = {
+      id: '1',
+      type: 'array',
+      items: null,
+      annotations: {
+        examples: {},
+      },
+      validations: {},
+      path: [],
+    };
+
+    const wrapper = shallow(<Property node={node as SchemaNodeWithMeta} />);
+    expect(wrapper).not.toBeEmptyRender();
+  });
 });

src/components/shared/Property.tsx

@@ -1,6 +1,7 @@
 import { size as _size } from 'lodash-es';
 import * as React from 'react';
 import { GoToRefHandler, IArrayNode, IObjectNode, SchemaKind, SchemaNodeWithMeta } from '../../types';
+import { isArrayNodeWithItems } from '../../utils/guards';
 import { inferType } from '../../utils/inferType';
 import { isCombinerNode, isRefNode } from '../../utils/nodes';
 import { Types } from './Types';
@@ -12,10 +13,7 @@ export interface IProperty {
 
 export const Property: React.FunctionComponent<IProperty> = ({ node, onGoToRef }) => {
   const type = isRefNode(node) ? '$ref' : isCombinerNode(node) ? node.combiner : node.type;
-  const subtype =
-    type === SchemaKind.Array && (node as IArrayNode).items !== undefined
-      ? inferType((node as IArrayNode).items!)
-      : undefined;
+  const subtype = isArrayNodeWithItems(node) ? inferType(node.items) : undefined;
 
   const childrenCount = React.useMemo<number | null>(
     () => {

src/utils/guards.ts

@@ -0,0 +1,8 @@
+import { JSONSchema4 } from 'json-schema';
+import { isObjectLike as _isObjectLike } from 'lodash-es';
+import { IArrayNode, SchemaKind, SchemaNode } from '../types';
+
+export const isArrayNodeWithItems = (
+  node: SchemaNode,
+): node is Omit<IArrayNode, 'items'> & { items: JSONSchema4 | JSONSchema4[] } =>
+  'type' in node && 'items' in node && node.type === SchemaKind.Array && _isObjectLike(node.items);