fix(@angular/cli): handle oneOf when converting schema to yargs options

This change fixes JSONSchemas where `oneOf` is placed at the root of the
schema rather than in an array's `items`. This allows an array to be
passed via the command-line, but additional types to be represented via
configuration.

Author: terencehonles

packages/angular/cli/src/command-builder/utilities/json-schema.ts

@@ -156,6 +156,10 @@ function isSupportedArrayItemSchema(schema: json.JsonObject): boolean {
     return true;
   }
 
+  if (isJsonObject(schema.items)) {
+    return isSupportedArrayItemSchema(schema.items);
+  }
+
   if (json.isJsonArray(schema.items)) {
     return schema.items.some((item) => isJsonObject(item) && isSupportedArrayItemSchema(item));
   }
@@ -198,7 +202,7 @@ function getSupportedTypes(
       case 'string':
         return true;
       case 'array':
-        return isJsonObject(current.items) && isSupportedArrayItemSchema(current.items);
+        return isSupportedArrayItemSchema(current);
       case 'object':
         return isStringMap(current);
       default:

packages/angular/cli/src/command-builder/utilities/json-schema_spec.ts

@@ -116,6 +116,12 @@ describe('parseJsonSchemaToOptions', () => {
               ],
             },
           },
+          'oneOfAtRoot': {
+            'oneOf': [
+              {'type': 'array', 'items': {'type': 'string'}},
+              {'type': 'boolean'},
+            ]
+          }
         },
       };
       const registry = new schema.CoreSchemaRegistry();
@@ -199,6 +205,21 @@ describe('parseJsonSchemaToOptions', () => {
       });
     });
 
+    describe('type=array, oneOf at root', () => {
+      it('parses valid option value', async () => {
+        expect(
+          await parse([
+            '--oneOfAtRoot',
+            'first',
+            '--oneOfAtRoot',
+            'second',
+            '--oneOfAtRoot',
+            'third',
+          ]),
+        ).toEqual(jasmine.objectContaining({'oneOfAtRoot': ['first', 'second', 'third']}));
+      });
+    });
+
     describe('type=string, enum', () => {
       it('parses valid option value', async () => {
         expect(await parse(['--ssr', 'never'])).toEqual(