add preprocessor

lib/index.d.ts

@@ -1,5 +1,5 @@
 import { JSONSchema4, JSONSchema4Type, JSONSchema6, JSONSchema6Type } from "json-schema";
-import { RequestInit } from "node-fetch";
+import { Request, RequestInit } from "node-fetch";
 
 export = $RefParser;
 
@@ -240,6 +240,16 @@ declare namespace $RefParser {
  * Provide `RequestInit` on HTTP Resolver
  */
  requestInit?: RequestInit;
+
+ /**
+ * pre process `Request` object on HTTP Resolver
+ *
+ * e.g:
+ * 1. modify request method
+ * 2. re-mapping url
+ * etc
+ */
+ preprocessor?(request: Request): Request;
  }
 
  /**

lib/resolvers/http.js

@@ -1,11 +1,18 @@
 "use strict";
 
 const fetch = require("node-fetch").default;
+const Request = require("node-fetch").Request;
 const { ono } = require("@jsdevtools/ono");
 const url = require("../util/url");
 const { ResolverError } = require("../util/errors");
 
-module.exports = {
+module.exports = { /**
+ * The order that this resolver will run, in relation to other resolvers.
+ *
+ * @type {number}
+ */
+ order: 200,
+
  /**
  * fetch RequestInit defintion
  *
@@ -17,6 +24,16 @@ module.exports = {
  timeout: 5000
  },
 
+ /**
+ * HTTP Request preprocessor
+ *
+ * @param {Request} request
+ * @returns {Request}
+ */
+ preprocessor (request) {
+ return request;
+ },
+
  /**
  * Determines whether this resolver can read a given file reference.
  * Resolvers that return true will be tried in order, until one successfully resolves the file.
@@ -47,7 +64,9 @@ module.exports = {
  u.protocol = url.parse(location.href).protocol;
  }
 
- return fetch(url.format(u), this.requestInit)
+ const request = new Request(url.format(u), this.requestInit);
+
+ return fetch(this.preprocessor(request))
  .then((response) => response.buffer())
  .catch((err) => new ResolverError(ono(err, `Error downloading ${u.href}`), u.href));
  }