Add support for navigator.userAgent, closes #209

Author: mrbbot

packages/core/src/plugins/core.ts

@@ -42,6 +42,7 @@ import {
   DOMException,
   FetchEvent,
   FixedLengthStream,
+  Navigator,
   Request,
   Response,
   ScheduledEvent,
@@ -365,6 +366,12 @@ export class CorePlugin extends Plugin<CoreOptions> implements CoreOptions {
       CompatResponse = proxyStringFormDataFiles(CompatResponse);
     }
 
+    // Only include `navigator` if `global_navigator` compatibility flag is set
+    const compatGlobals: Context = {};
+    if (ctx.compat.isEnabled("global_navigator")) {
+      compatGlobals.navigator = new Navigator();
+    }
+
     // Try to parse upstream URL if set
     try {
       this.upstreamURL =
@@ -449,6 +456,8 @@ export class CorePlugin extends Plugin<CoreOptions> implements CoreOptions {
       // Approximate with serialize/deserialize if not there.
       structuredClone: globalThis.structuredClone ?? structuredCloneBuffer,
 
+      ...compatGlobals,
+
       // The types below would be included automatically, but it's not possible
       // to create instances of them without using their constructors and they
       // may be returned from Miniflare's realm (e.g. ArrayBuffer responses,

packages/core/src/standards/index.ts

@@ -43,4 +43,5 @@ export type {
 } from "./http";
 export { FixedLengthStream } from "./streams";
 export type { ArrayBufferViewConstructor } from "./streams";
+export * from "./navigator";
 export * from "./timers";

packages/core/src/standards/navigator.ts

@@ -0,0 +1,3 @@
+export class Navigator {
+  readonly userAgent = "Cloudflare-Workers";
+}

packages/core/test/plugins/core.spec.ts

@@ -497,6 +497,17 @@ test("CorePlugin: setup: Response parses files in FormData as File objects only
   resFormData = await res.formData();
   t.true(resFormData.get("file") instanceof File);
 });
+test("CorePlugin: setup: includes navigator only if compatibility flag enabled", async (t) => {
+  let plugin = new CorePlugin(ctx);
+  let globals = (await plugin.setup()).globals;
+  t.is(globals?.navigator, undefined);
+
+  const compat = new Compatibility(undefined, ["global_navigator"]);
+  plugin = new CorePlugin({ log, compat, rootPath });
+  globals = (await plugin.setup()).globals;
+  t.is(globals?.navigator.userAgent, "Cloudflare-Workers");
+});
+
 test("CorePlugin: setup: structuredClone: creates deep-copy of value", async (t) => {
   const plugin = new CorePlugin(ctx);
   const { globals } = await plugin.setup();

packages/core/test/standards/navigator.spec.ts

@@ -0,0 +1,7 @@
+import { Navigator } from "@miniflare/core";
+import test from "ava";
+
+test("Navigator: userAgent is Cloudflare-Workers", (t) => {
+  const navigator = new Navigator();
+  t.is(navigator.userAgent, "Cloudflare-Workers");
+});

packages/shared/src/compat.ts

@@ -11,11 +11,13 @@ export interface CompatibilityFeature {
 // will get a type error if they try to use an unsupported flag via the API,
 // and they won't be logged in the "Enabled Compatibility Flags" section.
 export type CompatibilityEnableFlag =
+  | "global_navigator"
   | "durable_object_fetch_requires_full_url"
   | "fetch_refuses_unknown_protocols"
   | "formdata_parser_supports_files"
   | "html_rewriter_treats_esi_include_as_void_tag";
 export type CompatibilityDisableFlag =
+  | "no_global_navigator"
   | "durable_object_fetch_allows_relative_url"
   | "fetch_treats_unknown_protocols_as_http"
   | "formdata_parser_converts_files_to_strings";
@@ -24,6 +26,11 @@ export type CompatibilityFlag =
   | CompatibilityDisableFlag;
 
 const FEATURES: CompatibilityFeature[] = [
+  {
+    defaultAsOf: "2022-03-21",
+    enableFlag: "global_navigator",
+    disableFlag: "no_global_navigator",
+  },
   {
     defaultAsOf: "2021-11-10",
     enableFlag: "durable_object_fetch_requires_full_url",