module: fix main lookup regression from nodejs#18728

Author: guybedford

src/module_wrap.cc

@@ -544,7 +544,7 @@ const PackageConfig& GetPackageConfig(Environment* env,
   }
 
   auto entry = env->package_json_cache.emplace(path,
-      PackageConfig { Exists::Yes, IsValid::Yes, has_main, "" });
+      PackageConfig { Exists::Yes, IsValid::Yes, has_main, main_std });
   return entry.first->second;
 }
 
@@ -585,13 +585,15 @@ Maybe<URL> ResolveMain(Environment* env, const URL& search) {
       GetPackageConfig(env, pkg.ToFilePath());
   // Note invalid package.json should throw in resolver
   // currently we silently ignore which is incorrect
-  if (!pjson.exists || !pjson.is_valid || !pjson.has_main) {
+  if (pjson.exists == Exists::No ||
+      pjson.is_valid == IsValid::No ||
+      pjson.has_main == HasMain::No) {
     return Nothing<URL>();
   }
   if (!ShouldBeTreatedAsRelativeOrAbsolutePath(pjson.main)) {
-    return Resolve(env, "./" + pjson.main, search);
+    return Resolve(env, "./" + pjson.main, search, IgnoreMain);
   }
-  return Resolve(env, pjson.main, search);
+  return Resolve(env, pjson.main, search, IgnoreMain);
 }
 
 Maybe<URL> ResolveModule(Environment* env,
@@ -602,7 +604,7 @@ Maybe<URL> ResolveModule(Environment* env,
   do {
     dir = parent;
     Maybe<URL> check =
-        Resolve(env, "./node_modules/" + specifier, dir, IgnoreMain);
+        Resolve(env, "./node_modules/" + specifier, dir, CheckMain);
     if (!check.IsNothing()) {
       const size_t limit = specifier.find('/');
       const size_t spec_len =

test/es-module/test-esm-main-lookup.mjs

@@ -0,0 +1,6 @@
+// Flags: --experimental-modules
+/* eslint-disable required-modules */
+import assert from 'assert';
+import main from '../fixtures/es-modules/pjson-main';
+
+assert.strictEqual(main, 'main');

test/fixtures/es-modules/pjson-main/main.js

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

test/fixtures/es-modules/pjson-main/package.json

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