doc: add doc for --loader option

PR-URL: #22104
Fixes: #21230
Reviewed-By: Benjamin Gruenbaum <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: John-David Dalton <[email protected]>

Author: SirR4T

doc/api/cli.md

@@ -132,6 +132,13 @@ V8 inspector integration allows tools such as Chrome DevTools and IDEs to debug
 and profile Node.js instances. The tools attach to Node.js instances via a
 tcp port and communicate using the [Chrome DevTools Protocol][].
 
+### `--loader=file`
+<!--
+added: v9.0.0
+-->
+
+Specify the `file` of the custom [experimental ECMAScript Module][] loader.
+
 ### `--napi-modules`
 <!-- YAML
 added: v7.10.0
@@ -686,4 +693,5 @@ greater than `4` (its current default value). For more information, see the
 [REPL]: repl.html
 [debugger]: debugger.html
 [emit_warning]: process.html#process_process_emitwarning_warning_type_code_ctor
+[experimental ECMAScript Module]: esm.html#esm_loader_hooks
 [libuv threadpool documentation]: http://docs.libuv.org/en/latest/threadpool.html

doc/node.1

@@ -124,6 +124,12 @@ Default is
 V8 Inspector integration allows attaching Chrome DevTools and IDEs to Node.js instances for debugging and profiling.
 It uses the Chrome DevTools Protocol.
 .
+.It Fl -loader Ns = Ns Ar file
+Specify the
+.Ar file
+as a custom loader, to load
+.Fl -experimental-modules .
+.
 .It Fl -napi-modules
 This option is a no-op.
 It is kept for compatibility.

src/node.cc

@@ -2633,6 +2633,9 @@ static void PrintHelp() {
          "  --inspect[=[host:]port]    activate inspector on host:port\n"
          "                             (default: 127.0.0.1:9229)\n"
 #endif  // HAVE_INSPECTOR
+         "  --loader=file              (with --experimental-modules) use the \n"
+         "                             specified file as a custom loader\n"
+         "                             for ECMAScript Modules \n"
          "  --napi-modules             load N-API modules (no-op - option\n"
          "                             kept for compatibility)\n"
          "  --no-deprecation           silence deprecation warnings\n"