esm: make specifier flag clearly experimental

`--es-module-specifier-resolution` is the only flagged portion of the
ESM implementation that does not have the word experimental in the flag
name. This commit changes the flag to:

`--experimental-specifier-resolution`

`--es-module-specifier-resolution` remains as an alias for backwards
compatibility but it is no longer documented.

PR-URL: https://github.com/nodejs/node/pull/30678
Reviewed-By: Jan Krems <jan.krems@gmail.com>
Reviewed-By: Guy Bedford <guybedford@gmail.com>

1 files changed, 8 insertions, 4 deletions

diff --git a/lib/internal/modules/esm/default_resolve.js b/lib/internal/modules/esm/default_resolve.js
index 169c6f3569..c9ef3883c4 100644
--- a/lib/internal/modules/esm/default_resolve.js
+++ b/lib/internal/modules/esm/default_resolve.js
@@ -13,8 +13,8 @@ const { getOptionValue } = require('internal/options');
 const preserveSymlinks = getOptionValue('--preserve-symlinks');
 const preserveSymlinksMain = getOptionValue('--preserve-symlinks-main');
 const experimentalJsonModules = getOptionValue('--experimental-json-modules');
-const esModuleSpecifierResolution =
-  getOptionValue('--es-module-specifier-resolution');
+const experimentalSpeciferResolution =
+  getOptionValue('--experimental-specifier-resolution');
 const typeFlag = getOptionValue('--input-type');
 const experimentalWasmModules = getOptionValue('--experimental-wasm-modules');
 const { resolve: moduleWrapResolve,
@@ -110,10 +110,14 @@ function resolve(specifier, parentURL) {
   if (ext === '.js' || (!format && isMain))
     format = getPackageType(url.href) === TYPE_MODULE ? 'module' : 'commonjs';
   if (!format) {
-    if (esModuleSpecifierResolution === 'node')
+    if (experimentalSpeciferResolution === 'node') {
+      process.emitWarning(
+        'The Node.js specifier resolution in ESM is experimental.',
+        'ExperimentalWarning');
       format = legacyExtensionFormatMap[ext];
-    else
+    } else {
       throw new ERR_UNKNOWN_FILE_EXTENSION(fileURLToPath(url));
+    }
   }
   return { url: `${url}`, format };
 }