lib: enable fetch by default

doc/api/cli.md

@@ -280,14 +280,6 @@ effort to report stack traces relative to the original source file.
 Overriding `Error.prepareStackTrace` prevents `--enable-source-maps` from
 modifying the stack trace.
 
-### `--experimental-fetch`
-
-<!-- YAML
-added: v17.5.0
--->
-
-Enable experimental support for the [Fetch API][].
-
 ### `--experimental-global-webcrypto`
 
 <!-- YAML
@@ -333,6 +325,14 @@ added: v11.8.0
 
 Use the specified file as a security policy.
 
+### `--no-experimental-fetch`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+Disable experimental support for the [Fetch API][].
+
 ### `--no-experimental-repl-await`
 
 <!-- YAML
@@ -1587,7 +1587,6 @@ Node.js options that are allowed are:
 * `--enable-fips`
 * `--enable-source-maps`
 * `--experimental-abortcontroller`
-* `--experimental-fetch`
 * `--experimental-global-webcrypto`
 * `--experimental-import-meta-resolve`
 * `--experimental-json-modules`
@@ -1617,6 +1616,7 @@ Node.js options that are allowed are:
 * `--napi-modules`
 * `--no-addons`
 * `--no-deprecation`
+* `--no-experimental-fetch`
 * `--no-experimental-repl-await`
 * `--no-extra-info-on-fatal-exception`
 * `--no-force-async-hooks-checks`

doc/api/globals.md

@@ -384,7 +384,7 @@ This variable may appear to be global but is not. See [`exports`][].
 added: v17.5.0
 -->
 
-> Stability: 1 - Experimental. Enable this API with the [`--experimental-fetch`][]
+> Stability: 1 - Experimental. Disable this API with the [`--no-experimental-fetch`][]
 > CLI flag.
 
 A browser-compatible implementation of the [`fetch()`][] function.
@@ -395,7 +395,7 @@ A browser-compatible implementation of the [`fetch()`][] function.
 added: REPLACEME
 -->
 
-> Stability: 1 - Experimental. Enable this API with the [`--experimental-fetch`][]
+> Stability: 1 - Experimental. Disable this API with the [`--no-experimental-fetch`][]
 > CLI flag.
 
 A browser-compatible implementation of {FormData}.
@@ -421,7 +421,7 @@ Node.js this is different. The top-level scope is not the global scope;
 added: v17.5.0
 -->
 
-> Stability: 1 - Experimental. Enable this API with the [`--experimental-fetch`][]
+> Stability: 1 - Experimental. Disable this API with the [`--no-experimental-fetch`][]
 > CLI flag.
 
 A browser-compatible implementation of {Headers}.
@@ -526,7 +526,7 @@ This variable may appear to be global but is not. See [`require()`][].
 added: v17.5.0
 -->
 
-> Stability: 1 - Experimental. Enable this API with the [`--experimental-fetch`][]
+> Stability: 1 - Experimental. Disable this API with the [`--no-experimental-fetch`][]
 > CLI flag.
 
 A browser-compatible implementation of {Response}.
@@ -537,7 +537,7 @@ A browser-compatible implementation of {Response}.
 added: v17.5.0
 -->
 
-> Stability: 1 - Experimental. Enable this API with the [`--experimental-fetch`][]
+> Stability: 1 - Experimental. Disable this API with the [`--no-experimental-fetch`][]
 > CLI flag.
 
 A browser-compatible implementation of {Request}.
@@ -660,8 +660,8 @@ The object that acts as the namespace for all W3C
 [Mozilla Developer Network][webassembly-mdn] for usage and compatibility.
 
 [Web Crypto API]: webcrypto.md
-[`--experimental-fetch`]: cli.md#--experimental-fetch
 [`--experimental-global-webcrypto`]: cli.md#--experimental-global-webcrypto
+[`--no-experimental-fetch`]: cli.md#--no-experimental-fetch
 [`AbortController`]: https://developer.mozilla.org/en-US/docs/Web/API/AbortController
 [`DOMException`]: https://developer.mozilla.org/en-US/docs/Web/API/DOMException
 [`EventTarget` and `Event` API]: events.md#eventtarget-and-event-api

doc/node.1

@@ -139,9 +139,6 @@ Requires Node.js to be built with
 .It Fl -enable-source-maps
 Enable Source Map V3 support for stack traces.
 .
-.It Fl -experimental-fetch
-Enable experimental support for the Fetch API.
-.
 .It Fl -experimental-global-webcrypto
 Expose the Web Crypto API on the global scope.
 .
@@ -159,6 +156,9 @@ Enable experimental support for loading modules using `import` over `https:`.
 .It Fl -experimental-policy
 Use the specified file as a security policy.
 .
+.It Fl -no-experimental-fetch
+Disable experimental support for the Fetch API.
+.
 .It Fl -no-experimental-repl-await
 Disable top-level await keyword support in REPL.
 .

lib/internal/bootstrap/pre_execution.js

@@ -2,6 +2,7 @@
 
 const {
   NumberParseInt,
+  ObjectDefineProperties,
   ObjectDefineProperty,
   ObjectGetOwnPropertyDescriptor,
   SafeMap,
@@ -152,18 +153,45 @@ function setupWarningHandler() {
 // https://fetch.spec.whatwg.org/
 function setupFetch() {
   if (process.config.variables.node_no_browser_globals ||
-      !getOptionValue('--experimental-fetch')) {
+      getOptionValue('--no-experimental-fetch')) {
     return;
   }
 
-  emitExperimentalWarning('Fetch');
+  let undici;
+  function lazyUndici() {
+    if (undici) {
+      return undici;
+    }
+
+    emitExperimentalWarning('The Fetch API');
+    undici = require('internal/deps/undici/undici');
+  }
+
+  async function fetch(input, init = undefined) {
+    return lazyUndici().fetch(input, init);
+  }
+
+  defineOperation(globalThis, 'fetch', fetch);
 
-  const undici = require('internal/deps/undici/undici');
-  defineOperation(globalThis, 'fetch', undici.fetch);
-  exposeInterface(globalThis, 'FormData', undici.FormData);
-  exposeInterface(globalThis, 'Headers', undici.Headers);
-  exposeInterface(globalThis, 'Request', undici.Request);
-  exposeInterface(globalThis, 'Response', undici.Response);
+  function lazyInterface(name) {
+    return {
+      configurable: true,
+      enumerable: false,
+      get() {
+        return lazyUndici()[name];
+      },
+      set(value) {
+        exposeInterface(globalThis, name, value);
+      }
+    };
+  }
+
+  ObjectDefineProperties(globalThis, {
+    FormData: lazyInterface('FormData'), 
+    Headers: lazyInterface('Headers'),
+    Request: lazyInterface('Request'),
+    Response: lazyInterface('Response'),
+  });
 }
 
 // TODO(aduh95): move this to internal/bootstrap/browser when the CLI flag is

src/node_options.cc

@@ -318,7 +318,8 @@ EnvironmentOptionsParser::EnvironmentOptionsParser() {
   AddOption("--experimental-fetch",
             "experimental Fetch API",
             &EnvironmentOptions::experimental_fetch,
-            kAllowedInEnvironment);
+            kAllowedInEnvironment,
+            true);
   AddOption("--experimental-global-webcrypto",
             "expose experimental Web Crypto API on the global scope",
             &EnvironmentOptions::experimental_global_web_crypto,

src/node_options.h

@@ -107,7 +107,7 @@ class EnvironmentOptions : public Options {
   std::vector<std::string> conditions;
   std::string dns_result_order;
   bool enable_source_maps = false;
-  bool experimental_fetch = false;
+  bool experimental_fetch = true;
   bool experimental_global_web_crypto = false;
   bool experimental_https_modules = false;
   std::string experimental_specifier_resolution;

test/parallel/test-fetch-disabled.mjs

@@ -1,3 +1,4 @@
+// Flags: --no-experimental-fetch
 import '../common/index.mjs';
 
 import assert from 'assert';

test/parallel/test-fetch.mjs

@@ -1,6 +1,4 @@
-// Flags: --experimental-fetch --no-warnings
-
-import '../common/index.mjs';
+import * as common from '../common/index.mjs';
 
 import assert from 'assert';
 import events from 'events';
@@ -12,6 +10,11 @@ assert.strictEqual(typeof globalThis.Headers, 'function');
 assert.strictEqual(typeof globalThis.Request, 'function');
 assert.strictEqual(typeof globalThis.Response, 'function');
 
+common.expectWarning(
+  'ExperimentalWarning',
+  'The Fetch API is an experimental feature. This feature could change at any time'
+);
+
 const server = http.createServer((req, res) => {
   // TODO: Remove this once keep-alive behavior can be disabled from the client
   // side.