feat: Ability to modify headers and custom fetch implementation

package.json

@@ -31,7 +31,8 @@
   },
   "homepage": "https://github.com/resendlabs/resend-node#readme",
   "dependencies": {
-    "@react-email/render": "0.0.9"
+    "@react-email/render": "0.0.9",
+    "undici": "^5.27.2"
   },
   "devDependencies": {
     "@types/jest": "29.5.7",

src/interfaces.ts

@@ -1,3 +1,12 @@
+import type { fetch } from 'undici';
+
+export type Fetch = typeof fetch;
+
+export type Options = {
+  fetch?: Fetch;
+  headers?: Record<string, string>;
+};
+
 export const RESEND_ERROR_CODES_BY_KEY = {
   missing_required_field: 422,
   invalid_access: 422,

src/resend.ts

@@ -7,12 +7,14 @@ import { Contacts } from './contacts/contacts';
 import { Domains } from './domains/domains';
 import { Emails } from './emails/emails';
 import { isResendErrorResponse } from './guards';
-import { ErrorResponse } from './interfaces';
+import { ErrorResponse, Fetch, Options } from './interfaces';
+import { fetch } from 'undici';
 
 const baseUrl = process.env.RESEND_BASE_URL || 'https://api.resend.com';
 const userAgent = process.env.RESEND_USER_AGENT || `resend-node:${version}`;
 
 export class Resend {
+  private readonly fetch: Fetch = fetch;
   private readonly headers: Headers;
 
   readonly apiKeys = new ApiKeys(this);
@@ -22,7 +24,10 @@ export class Resend {
   readonly domains = new Domains(this);
   readonly emails = new Emails(this);
 
-  constructor(readonly key?: string) {
+  constructor(
+    readonly key?: string,
+    options: Options = {},
+  ) {
     if (!key) {
       this.key = process.env.RESEND_API_KEY;
 
@@ -33,29 +38,39 @@ export class Resend {
       }
     }
 
+    if (options.fetch) {
+      this.fetch = options.fetch;
+    }
+
     this.headers = new Headers({
       Authorization: `Bearer ${this.key}`,
       'User-Agent': userAgent,
       'Content-Type': 'application/json',
     });
+
+    if (options.headers) {
+      for (const [key, value] of Object.entries(options.headers)) {
+        this.headers.set(key, value);
+      }
+    }
   }
 
   async fetchRequest<T>(
     path: string,
     options = {},
   ): Promise<{ data: T | null; error: ErrorResponse | null }> {
-    const response = await fetch(`${baseUrl}${path}`, options);
+    const response = await this.fetch(`${baseUrl}${path}`, options);
 
     if (!response.ok) {
-      const error = await response.json();
+      const error = (await response.json()) as any;
       if (isResendErrorResponse(error)) {
         return { data: null, error };
       }
 
       return { data: null, error };
     }
 
-    const data = await response.json();
+    const data = (await response.json()) as any;
     return { data, error: null };
   }
 

yarn.lock

@@ -498,6 +498,13 @@ __metadata:
   languageName: node
   linkType: hard
 
+"@fastify/busboy@npm:^2.0.0":
+  version: 2.1.0
+  resolution: "@fastify/busboy@npm:2.1.0"
+  checksum: 3233abd10f73e50668cb4bb278a79b7b3fadd30215ac6458299b0e5a09a29c3586ec07597aae6bd93f5cbedfcef43a8aeea51829cd28fc13850cdbcd324c28d5
+  languageName: node
+  linkType: hard
+
 "@humanwhocodes/config-array@npm:^0.11.13":
   version: 0.11.13
   resolution: "@humanwhocodes/config-array@npm:0.11.13"
@@ -4318,6 +4325,7 @@ __metadata:
     ts-jest: 29.1.1
     ts-node: 10.9.1
     typescript: 5.2.2
+    undici: ^5.27.2
   languageName: unknown
   linkType: soft
 
@@ -4897,6 +4905,15 @@ __metadata:
   languageName: node
   linkType: hard
 
+"undici@npm:^5.27.2":
+  version: 5.27.2
+  resolution: "undici@npm:5.27.2"
+  dependencies:
+    "@fastify/busboy": ^2.0.0
+  checksum: 22bbdd763798700979986546d70072b67223189353d2a811efa9c6e44476161a0d1781ffe24115221f69a1b344b95d5926bd39a6eb760a2cd8804781cec0c5eb
+  languageName: node
+  linkType: hard
+
 "unique-filename@npm:^3.0.0":
   version: 3.0.0
   resolution: "unique-filename@npm:3.0.0"