feat(http/unstable): add support for extra headers in serveFile

http/file_server_test.ts

@@ -24,6 +24,7 @@ import { getAvailablePort } from "@std/net/get-available-port";
 import { concat } from "@std/bytes/concat";
 import { lessThan, parse as parseSemver } from "@std/semver";
 import { serveDir as unstableServeDir } from "./unstable_file_server.ts";
+import { serveFile as unstableServeFile } from "./unstable_file_server.ts";
 
 const moduleDir = dirname(fromFileUrl(import.meta.url));
 const testdataDir = resolve(moduleDir, "testdata");
@@ -1176,3 +1177,14 @@ Deno.test("(unstable) serveDir() does not shadow existing files and directory if
   assertEquals(res.status, 301);
   assertEquals(res.headers.has("location"), true);
 });
+
+Deno.test("(unstable) serveFile() sends custom headers", async () => {
+  const req = new Request("http://localhost/testdata/test_file.txt");
+  const res = await unstableServeFile(req, TEST_FILE_PATH, {
+    headers: ["X-Extra: extra header"],
+  });
+
+  assertEquals(res.status, 200);
+  assertEquals(res.headers.get("X-Extra"), "extra header");
+  assertEquals(await res.text(), TEST_FILE_TEXT);
+});

http/unstable_file_server.ts

@@ -3,8 +3,9 @@
 import {
   serveDir as stableServeDir,
   type ServeDirOptions as StableServeDirOptions,
+  serveFile as stableServeFile,
+  type ServeFileOptions as StableServeFileOptions,
 } from "./file_server.ts";
-export { serveFile, type ServeFileOptions } from "./file_server.ts";
 
 /**
  * Serves the files under the given directory root (opts.fsRoot).
@@ -61,3 +62,50 @@ export interface ServeDirOptions extends StableServeDirOptions {
    */
   cleanUrls?: boolean;
 }
+
+/** Interface for serveFile options. */
+export interface ServeFileOptions extends StableServeFileOptions {
+  /** Headers to add to each response
+   *
+   * @default {[]}
+   */
+  headers?: string[];
+}
+
+/**
+ * Resolves a {@linkcode Response} with the requested file as the body.
+ *
+ * @experimental **UNSTABLE**: New API, yet to be vetted.
+ *
+ * @example Usage
+ * ```ts ignore
+ * import { serveFile } from "@std/http/file-server";
+ *
+ * Deno.serve((req) => {
+ *   return serveFile(req, "README.md");
+ * });
+ * ```
+ *
+ * @param req The server request context used to cleanup the file handle.
+ * @param filePath Path of the file to serve.
+ * @param options Additional options.
+ * @returns A response for the request.
+ */
+export async function serveFile(
+  req: Request,
+  filePath: string,
+  options?: ServeFileOptions,
+): Promise<Response> {
+  const response = await stableServeFile(req, filePath, options);
+
+  if (options?.headers) {
+    for (const header of options.headers) {
+      const headerSplit = header.split(":");
+      const name = headerSplit[0]!;
+      const value = headerSplit.slice(1).join(":");
+      response.headers.append(name, value);
+    }
+  }
+
+  return response;
+}