module: fix legacy node specifier resolution to resolve "main" field

PR-URL: #38979 Backport-PR-URL: #39497 Fixes: #32103 Fixes: #38739 Reviewed-By: Bradley Farias <bradley.meck@gmail.com> Reviewed-By: Guy Bedford <guybedford@gmail.com>

Author: aduh95

lib/internal/modules/esm/resolve.js

@@ -30,7 +30,7 @@ const {
  Stats,
 } = require('fs');
 const { getOptionValue } = require('internal/options');
-const { sep, relative } = require('path');
+const { sep, relative, resolve } = require('path');
 const preserveSymlinks = getOptionValue('--preserve-symlinks');
 const preserveSymlinksMain = getOptionValue('--preserve-symlinks-main');
 const typeFlag = getOptionValue('--input-type');
@@ -160,16 +160,18 @@ function getPackageScopeConfig(resolved) {
  return packageConfig;
 }
 
-/*
+/**
  * Legacy CommonJS main resolution:
  * 1. let M = pkg_url + (json main field)
  * 2. TRY(M, M.js, M.json, M.node)
  * 3. TRY(M/index.js, M/index.json, M/index.node)
  * 4. TRY(pkg_url/index.js, pkg_url/index.json, pkg_url/index.node)
  * 5. NOT_FOUND
+ * @param {string | URL} url
+ * @returns {boolean}
  */
 function fileExists(url) {
- return tryStatSync(fileURLToPath(url)).isFile();
+ return tryStatSync(url).isFile();
 }
 
 function legacyMainResolve(packageJSONUrl, packageConfig, base) {
@@ -236,7 +238,19 @@ function resolveExtensions(search) {
  return undefined;
 }
 
-function resolveIndex(search) {
+function resolveDirectoryEntry(search) {
+ const dirPath = fileURLToPath(search);
+ const pkgJsonPath = resolve(dirPath, 'package.json');
+ if (fileExists(pkgJsonPath)) {
+ const pkgJson = packageJsonReader.read(pkgJsonPath);
+ if (pkgJson.containsKeys) {
+ const { main } = JSONParse(pkgJson.string);
+ if (main != null) {
+ const mainUrl = pathToFileURL(resolve(dirPath, main));
+ return resolveExtensionsWithTryExactName(mainUrl);
+ }
+ }
+ }
  return resolveExtensions(new URL('index', search));
 }
 
@@ -252,10 +266,10 @@ function finalizeResolution(resolved, base) {
  let file = resolveExtensionsWithTryExactName(resolved);
  if (file !== undefined) return file;
  if (!StringPrototypeEndsWith(path, '/')) {
- file = resolveIndex(new URL(`${resolved}/`));
+ file = resolveDirectoryEntry(new URL(`${resolved}/`));
  if (file !== undefined) return file;
  } else {
- return resolveIndex(resolved) || resolved;
+ return resolveDirectoryEntry(resolved) || resolved;
  }
  throw new ERR_MODULE_NOT_FOUND(
  resolved.pathname, fileURLToPath(base), 'module');

test/es-module/test-esm-specifiers-legacy-flag.mjs

@@ -6,12 +6,15 @@ import assert from 'assert';
 import commonjs from '../fixtures/es-module-specifiers/package-type-commonjs';
 // esm index.js
 import module from '../fixtures/es-module-specifiers/package-type-module';
+// Directory entry with main.js
+import main from '../fixtures/es-module-specifiers/dir-with-main';
 // Notice the trailing slash
 import success, { explicit, implicit, implicitModule }
  from '../fixtures/es-module-specifiers/';
 
 assert.strictEqual(commonjs, 'commonjs');
 assert.strictEqual(module, 'module');
+assert.strictEqual(main, 'main');
 assert.strictEqual(success, 'success');
 assert.strictEqual(explicit, 'esm');
 assert.strictEqual(implicit, 'cjs');

test/fixtures/es-module-specifiers/dir-with-main/main.js

@@ -0,0 +1 @@
+module.exports = 'main';

test/fixtures/es-module-specifiers/dir-with-main/package.json

@@ -0,0 +1,3 @@
+{
+ "main": "./main.js"
+}