fixup: support both flags and give proper warnings

src/node_options.cc

@@ -127,7 +127,20 @@ void EnvironmentOptions::CheckOptions(std::vector<std::string>* errors) {
     }
   }
 
-  if (!experimental_specifier_resolution.empty()) {
+  if (!es_module_specifier_resolution.empty()) {
+    if (!experimental_specifier_resolution.empty()) {
+      errors->push_back(
+        "bad option: cannot use --es-module-specifier-resolution"
+        " and --experimental-specifier-resolution at the same time");
+    } else {
+      experimental_specifier_resolution = es_module_specifier_resolution;
+      if (experimental_specifier_resolution != "node" &&
+          experimental_specifier_resolution != "explicit") {
+        errors->push_back(
+          "invalid value for --es-module-specifier-resolution");
+      }
+    }
+  } else if (!experimental_specifier_resolution.empty()) {
     if (experimental_specifier_resolution != "node" &&
         experimental_specifier_resolution != "explicit") {
       errors->push_back(
@@ -367,6 +380,11 @@ EnvironmentOptionsParser::EnvironmentOptionsParser() {
             "either 'explicit' (default) or 'node'",
             &EnvironmentOptions::experimental_specifier_resolution,
             kAllowedInEnvironment);
+  AddOption("--es-module-specifier-resolution",
+            "Select extension resolution algorithm for es modules; "
+            "either 'explicit' (default) or 'node'",
+            &EnvironmentOptions::es_module_specifier_resolution,
+            kAllowedInEnvironment);
   AddOption("--no-deprecation",
             "silence deprecation warnings",
             &EnvironmentOptions::no_deprecation,

src/node_options.h

@@ -105,6 +105,7 @@ class EnvironmentOptions : public Options {
   bool experimental_json_modules = false;
   bool experimental_resolve_self = false;
   std::string experimental_specifier_resolution;
+  std::string es_module_specifier_resolution;
   bool experimental_wasm_modules = false;
   std::string module_type;
   std::string experimental_policy;

test/es-module/test-esm-specifiers-both-flags.mjs

@@ -1,24 +1,16 @@
-import '../common/index.mjs';
+import { mustCall } from '../common/index.mjs';
 import { exec } from 'child_process';
-import { ok, strictEqual } from 'assert';
+import assert from 'assert';
 
-const expectedMessage = [
-  'Command failed: node --es-module-specifier-resolution=node',
-  ' --experimental-specifier-resolution=node\n',
-  'node: bad option: cannot use --es-module-specifier-resolution',
-  'and --experimental-specifier-resolution at the same time'
-].join(' ');
+const expectedError =
+  'node: bad option: cannot use --es-module-specifier-resolution ' +
+  'and --experimental-specifier-resolution at the same time';
 
-function handleError(error, stdout, stderr) {
-  ok(error);
-  strictEqual(error.message, expectedMessage);
-}
-
-const flags = [
-  '--es-module-specifier-resolution=node',
-  '--experimental-specifier-resolution=node'
-].join(' ');
+const flags = '--es-module-specifier-resolution=node ' +
+              '--experimental-specifier-resolution=node';
 
 exec(`${process.execPath} ${flags}`, {
   timeout: 300
-}, handleError);
+}, mustCall((error) => {
+  assert(error.message.includes(expectedError));
+}));