fix: accept vnd.openapi+json (#133)

Author: soyuka

src/openapi3/parseOpenApi3Documentation.ts

@@ -1,6 +1,7 @@
 import { Api } from "../Api.js";
 import handleJson, { removeTrailingSlash } from "./handleJson.js";
 import type { OpenAPIV3 } from "openapi-types";
+import type { RequestInitExtended } from "./types";
 
 export interface ParsedOpenApi3Documentation {
   api: Api;
@@ -9,10 +10,16 @@ export interface ParsedOpenApi3Documentation {
 }
 
 export default function parseOpenApi3Documentation(
-  entrypointUrl: string
+  entrypointUrl: string,
+  options: RequestInitExtended = {}
 ): Promise<ParsedOpenApi3Documentation> {
   entrypointUrl = removeTrailingSlash(entrypointUrl);
-  return fetch(entrypointUrl)
+  let headers: HeadersInit | undefined =
+    typeof options.headers === "function" ? options.headers() : options.headers;
+  headers = new Headers(headers);
+  headers.append("Accept", "application/vnd.openapi+json");
+
+  return fetch(entrypointUrl, { ...options, headers: headers })
     .then((res) => Promise.all([res, res.json()]))
     .then(
       ([res, response]: [res: Response, response: OpenAPIV3.Document]) => {

src/openapi3/types.ts

@@ -0,0 +1,3 @@
+export interface RequestInitExtended extends Omit<RequestInit, "headers"> {
+  headers?: HeadersInit | (() => HeadersInit);
+}