fix(@ngtools/json-schema): values of non-existent objects should return undefined (angular#4300)

Also, we verify the value is null and return that instead if thats the case.

Author: hansl

packages/@ngtools/json-schema/src/schema-tree.spec.ts

@@ -27,6 +27,14 @@ describe('@ngtools/json-schema', () => {
       proto.oneOfKey2 = 'hello';
       expect(proto.oneOfKey2 instanceof Array).toBe(false);
     });
+
+    it('returns undefined for values that are non-existent', () => {
+      const proto: any = Object.create(null);
+      const root = new RootSchemaTreeNode(proto, { value: valueJson, schema: schemaJson });
+
+      const value = root.children['objectKey1'].children['objectKey'].children['stringKey'].get();
+      expect(value).toBe(undefined);
+    });
   });
 
 

packages/@ngtools/json-schema/src/schema-tree.ts

@@ -409,10 +409,12 @@ export abstract class LeafSchemaTreeNode<T> extends SchemaTreeNode<T> {
     if (!this.defined && this._forward) {
       return this._forward.get();
     }
-    if (!this.defined && this._default !== undefined) {
-      return this._default;
+    if (!this.defined) {
+      return this._default !== undefined ? this._default : undefined;
     }
-    return this._value === undefined ? undefined : this.convert(this._value);
+    return this._value === undefined
+      ? undefined
+      : (this._value === null ? null : this.convert(this._value));
   }
   set(v: T, force = false) {
     if (this.readOnly && !force) {