esm: refactor get_format

PR-URL: #53872 Reviewed-By: Geoffrey Booth <[email protected]> Reviewed-By: Paolo Insogna <[email protected]> Reviewed-By: Matteo Collina <[email protected]>

Author: aduh95

lib/internal/modules/esm/get_format.js

@@ -17,6 +17,7 @@ const{
  mimeToFormat,
 }=require('internal/modules/esm/formats');
 
+constdetectModule=getOptionValue('--experimental-detect-module');
 constexperimentalNetworkImports=
 getOptionValue('--experimental-network-imports');
 const{ containsModuleSyntax }=internalBinding('contextify');
@@ -33,6 +34,17 @@ const protocolHandlers ={
 'node:'(){return'builtin';},
 };
 
+/**
+ * Determine whether the given ambiguous source contains CommonJS or ES module syntax.
+ * @param{string | Buffer | undefined} source
+ * @param{URL} url
+ */
+functiondetectModuleFormat(source,url){
+if(!source){returndetectModule ? null : 'commonjs';}
+if(!detectModule){return'commonjs';}
+returncontainsModuleSyntax(`${source}`,fileURLToPath(url),url) ? 'module' : 'commonjs';
+}
+
 /**
  * @param{URL} parsed
  * @returns{string | null}
@@ -112,26 +124,23 @@ function getFileProtocolModuleFormat(url, context ={__proto__: null }, ignoreE
 default: {// The user did not pass `--experimental-default-type`.
 // `source` is undefined when this is called from `defaultResolve`;
 // but this gets called again from `defaultLoad`/`defaultLoadSync`.
-if(getOptionValue('--experimental-detect-module')){
-constformat=source ?
-(containsModuleSyntax(`${source}`,fileURLToPath(url),url) ? 'module' : 'commonjs') :
-null;
-if(format==='module'){
-// This module has a .js extension, a package.json with no `type` field, and ESM syntax.
-// Warn about the missing `type` field so that the user can avoid the performance penalty of detection.
-typelessPackageJsonFilesWarnedAbout??=newSafeSet();
-if(!typelessPackageJsonFilesWarnedAbout.has(pjsonPath)){
-constwarning=`${url} parsed as an ES module because module syntax was detected;`+
-` to avoid the performance penalty of syntax detection, add "type": "module" to ${pjsonPath}`;
-process.emitWarning(warning,{
-code: 'MODULE_TYPELESS_PACKAGE_JSON',
-});
-typelessPackageJsonFilesWarnedAbout.add(pjsonPath);
-}
+// For ambiguous files (no type field, .js extension) we return
+// undefined from `resolve` and re-run the check in `load`.
+constformat=detectModuleFormat(source,url);
+if(format==='module'){
+// This module has a .js extension, a package.json with no `type` field, and ESM syntax.
+// Warn about the missing `type` field so that the user can avoid the performance penalty of detection.
+typelessPackageJsonFilesWarnedAbout??=newSafeSet();
+if(!typelessPackageJsonFilesWarnedAbout.has(pjsonPath)){
+constwarning=`${url} parsed as an ES module because module syntax was detected;`+
+` to avoid the performance penalty of syntax detection, add "type": "module" to ${pjsonPath}`;
+process.emitWarning(warning,{
+code: 'MODULE_TYPELESS_PACKAGE_JSON',
+});
+typelessPackageJsonFilesWarnedAbout.add(pjsonPath);
 }
-returnformat;
 }
-return'commonjs';
+returnformat;
 }
 }
 }
@@ -154,15 +163,14 @@ function getFileProtocolModuleFormat(url, context ={__proto__: null }, ignoreE
 return'commonjs';
 }
 default: {// The user did not pass `--experimental-default-type`.
-if(getOptionValue('--experimental-detect-module')){
-if(!source){returnnull;}
-constformat=getFormatOfExtensionlessFile(url);
-if(format==='module'){
-returncontainsModuleSyntax(`${source}`,fileURLToPath(url),url) ? 'module' : 'commonjs';
-}
+if(!source){
+returnnull;
+}
+constformat=getFormatOfExtensionlessFile(url);
+if(format==='wasm'){
 returnformat;
 }
-return'commonjs';
+returndetectModuleFormat(source,url);
 }
 }
 }