fix: extend Node.js IncomingHttpHeaders in our Headers type (#346)

This commit extends Node.js IncomingHttpHeaders in our Headers type.
Changes the Headers type to make it more compatible with Node.js TypeScript projects.

Signed-off-by: Lance Ball <lball@redhat.com>

src/constants.ts

@@ -48,6 +48,6 @@ const CONSTANTS = Object.freeze({
     DATA_SCHEMA: "dataschema",
     DATA_BASE64: "data_base64",
   },
-});
+} as const);
 
 export default CONSTANTS;

src/message/index.ts

@@ -1,3 +1,4 @@
+import { IncomingHttpHeaders } from "http";
 import { CloudEvent } from "..";
 import { binary, deserialize, structured, isEvent } from "./http";
 import { headersFor } from "./http/headers";
@@ -18,8 +19,8 @@ export interface Binding {
  * Headers is an interface representing transport-agnostic headers as
  * key/value string pairs
  */
-export interface Headers {
+export interface Headers extends IncomingHttpHeaders {
-  [key: string]: string;
+  [key: string]: string | string[] | undefined;
 }
 
 /**

src/parsers.ts

@@ -2,7 +2,7 @@ import CONSTANTS from "./constants";
 import { isString, isDefinedOrThrow, isStringOrObjectOrThrow, ValidationError } from "./event/validation";
 
 export abstract class Parser {
-  abstract parse(payload: Record<string, unknown> | string): unknown;
+  abstract parse(payload: Record<string, unknown> | string | string[] | undefined): unknown;
 }
 
 export class JSONParser implements Parser {

test/integration/emitter_factory_test.ts

@@ -48,7 +48,7 @@ function superagentEmitter(message: Message, options?: Options): Promise<unknown
   }
   // set headers
   for (const key of Object.getOwnPropertyNames(message.headers)) {
-    post.set(key, message.headers[key]);
+    post.set(key, message.headers[key] as string);
   }
   return post.send(message.body as string);
 }

test/integration/message_test.ts

@@ -2,6 +2,7 @@ import path from "path";
 import fs from "fs";
 
 import { expect } from "chai";
+import { IncomingHttpHeaders } from "http";
 import { CloudEvent, CONSTANTS, Version } from "../../src";
 import { asBase64 } from "../../src/event/validation";
 import { Message, HTTP } from "../../src/message";
@@ -93,6 +94,25 @@ describe("HTTP transport", () => {
     }).to.throw;
   });
 
+  it("Can be created with Node's IncomingHttpHeaders", () => {
+    const headers: IncomingHttpHeaders = {
+      "content-type": CONSTANTS.DEFAULT_CE_CONTENT_TYPE,
+    };
+    const body = JSON.stringify({
+      id,
+      type,
+      source,
+      specversion: Version.V1,
+      data: { lunch: "tacos" },
+    });
+    const message: Message = {
+      headers,
+      body,
+    };
+    const event = HTTP.toEvent(message);
+    expect(event.data).to.deep.equal({ lunch: "tacos" });
+  });
+
   describe("Specification version V1", () => {
     const fixture: CloudEvent = new CloudEvent({
       specversion: Version.V1,