🏭 Add deferred callback chain.

.gitignore

@@ -60,3 +60,5 @@ typings/
 # IDE
 .vscode
 
+# Rollup typescript cache
+.rpt2_cache

README.md

@@ -11,7 +11,7 @@
   <a href="https://github.com/elbywan/wretch/blob/master/LICENSE"><img src="https://img.shields.io/badge/license-MIT-blue.svg" alt="license-badge" height="20"></a>
 </h1>
 <h4 align="center">
-	A tiny (&lt; 2.4Kb g-zipped) wrapper built around fetch with an intuitive syntax.
+	A tiny (&lt; 2.5Kb g-zipped) wrapper built around fetch with an intuitive syntax.
 </h4>
 <h5 align="center">
     <i>f[ETCH] [WR]apper</i>
@@ -427,6 +427,33 @@ reAuthOn401.url("/resource")
   .then(callback) // <- Will be called for the original OR the replayed promise result
 ```
 
+#### defer(callback: (originalRequest: Wretcher, url: string, options: Object) => Wretcher, clear = false)
+
+Defer wretcher methods that will be chained and called just before the request is performed.
+
+```js
+/* Small fictional example: deferred authentication */
+
+// If you cannot retrieve the auth token while configuring the wretch object you can use .defer to postpone the call
+const api = wretch("...").defer((w, url, options)  => {
+  // If we are hitting the route /user…
+  if(/\/user/.test(url)) {
+    const { token } = options.context
+    return w.auth(token)
+  }
+  return w
+})
+
+// ... //
+
+const token = await getToken(request.session.user)
+
+// .auth gets called here automatically
+api.options({
+  context: { token }
+}).get().res()
+```
+
 #### resolve(doResolve: (chain: ResponseChain, originalRequest: Wretcher) => ResponseChain | Promise<any>, clear = false)
 
 Programs a resolver which will automatically be injected to perform response chain tasks.

dist/wretcher.d.ts

@@ -4,6 +4,7 @@ import { ConfiguredMiddleware } from "./middleware";
 export declare type WretcherOptions = RequestInit & {
     [key: string]: any;
 };
+export declare type DeferredCallback = (wretcher: Wretcher, url: string, options: WretcherOptions) => Wretcher;
 /**
  * The Wretcher class used to perform easy fetch requests.
  *
@@ -15,9 +16,10 @@ export declare class Wretcher {
     _catchers: Map<number | string, (error: WretcherError, originalRequest: Wretcher) => void>;
     _resolvers: Array<(resolver: ResponseChain, originalRequest: Wretcher) => any>;
     _middlewares: ConfiguredMiddleware[];
-    protected constructor(_url: string, _options: WretcherOptions, _catchers?: Map<number | string, (error: WretcherError, originalRequest: Wretcher) => void>, _resolvers?: Array<(resolver: ResponseChain, originalRequest: Wretcher) => any>, _middlewares?: ConfiguredMiddleware[]);
+    _deferredChain: DeferredCallback[];
+    protected constructor(_url: string, _options: WretcherOptions, _catchers?: Map<number | string, (error: WretcherError, originalRequest: Wretcher) => void>, _resolvers?: Array<(resolver: ResponseChain, originalRequest: Wretcher) => any>, _middlewares?: ConfiguredMiddleware[], _deferredChain?: DeferredCallback[]);
     static factory(url?: string, opts?: WretcherOptions): Wretcher;
-    private selfFactory({url, options, catchers, resolvers, middlewares}?);
+    private selfFactory({url, options, catchers, resolvers, middlewares, deferredChain}?);
     /**
      * Sets the default fetch options used for every subsequent fetch call.
      * @param opts New default options
@@ -110,6 +112,10 @@ export declare class Wretcher {
      * @param doResolve : Resolver callback
      */
     resolve(doResolve: (chain: ResponseChain, originalRequest: Wretcher) => ResponseChain | Promise<any>, clear?: boolean): Wretcher;
+    /**
+     * Defer wretcher methods that will be chained and called just before the request is performed.
+     */
+    defer(callback: DeferredCallback, clear?: boolean): Wretcher;
     /**
      * Add middlewares to intercept a request before being sent.
      */