feat: support x-discriminator for OpenAPI 2

related to #496

Author: RomanHotsiy

src/services/models/Schema.ts

@@ -111,7 +111,7 @@ export class SchemaModel {
       return;
     }
 
-    if (!isChild && schema.discriminator !== undefined) {
+    if (!isChild && getDiscriminator(schema) !== undefined) {
       this.initDiscriminator(schema, parser);
       return;
     }
@@ -171,7 +171,8 @@ export class SchemaModel {
     },
     parser: OpenAPIParser,
   ) {
-    this.discriminatorProp = schema.discriminator!.propertyName;
+    const discriminator = getDiscriminator(schema)!;
+    this.discriminatorProp = discriminator.propertyName;
     const derived = parser.findDerived([...(schema.parentRefs || []), this._$ref]);
 
     if (schema.oneOf) {
@@ -184,7 +185,7 @@ export class SchemaModel {
       }
     }
 
-    const mapping = schema.discriminator!.mapping || {};
+    const mapping = discriminator.mapping || {};
     for (const name in mapping) {
       derived[mapping[name]] = name;
     }
@@ -257,3 +258,7 @@ function buildFields(
 
   return fields;
 }
+
+function getDiscriminator(schema: OpenAPISchema): OpenAPISchema['discriminator'] {
+  return schema.discriminator || schema['x-discriminator'];
+}

src/types/index.d.ts

@@ -1,5 +1,3 @@
 export * from './open-api';
 
-export type Diff<T extends string, U extends string> = ({ [P in T]: P } &
-  { [P in U]: never } & { [x: string]: never })[T];
-export type Omit<T, K extends keyof T> = { [P in Diff<keyof T, K>]: T[P] };
+export type Omit<T, K extends keyof T> = Pick<T, Exclude<keyof T, K>>;

src/types/open-api.d.ts

@@ -1,4 +1,4 @@
-import { Omit } from './';
+import { Omit } from './index';
 
 export interface OpenAPISpec {
   openapi: string;