strict self resolution opt-in

doc/api/esm.md

@@ -1207,7 +1207,8 @@ _defaultEnv_ is the conditional environment name priority array,
 >    encoded strings for _"/"_ or _"\\"_, then
 >    1. Throw an _Invalid Specifier_ error.
 > 1. Set _selfUrl_ to the result of
->    **SELF_REFERENCE_RESOLE**(_packageName_, _packageSubpath_, _parentURL_).
+>    **SELF_REFERENCE_RESOLE**(_packageName_, _packageSubpath_, _parentURL_,
+>    **true**).
 > 1. If _selfUrl_ isn't empty, return _selfUrl_.
 > 1. If _packageSubpath_ is _undefined_ and _packageName_ is a Node.js builtin
 >    module, then
@@ -1230,14 +1231,21 @@ _defaultEnv_ is the conditional environment name priority array,
 >             1. Return **PACKAGE_EXPORTS_RESOLVE**(_packageURL_,
 >                _packageSubpath_, _pjson.exports_).
 >       1. Return the URL resolution of _packageSubpath_ in _packageURL_.
+> 1. Set _selfUrl_ to the result of
+>    **SELF_REFERENCE_RESOLE**(_packageName_, _packageSubpath_, _parentURL_,
+>    **false**).
+> 1. If _selfUrl_ isn't empty, return _selfUrl_.
 > 1. Throw a _Module Not Found_ error.
 
-**SELF_REFERENCE_RESOLVE**(_packageName_, _packageSubpath_, _parentURL_)
+**SELF_REFERENCE_RESOLVE**(_packageName_, _packageSubpath_, _parentURL_,
+                           _encapsulated_)
 
 > 1. Let _packageURL_ be the result of **READ_PACKAGE_SCOPE**(_parentURL_).
 > 1. If _packageURL_ is **null**, then
->    1. Return an empty result.
+>    1. Return **undefined**.
 > 1. Let _pjson_ be the result of **READ_PACKAGE_JSON**(_packageURL_).
+> 1. If _encapsulated_ is **true** and _pjson_ does not include an
+>    _"exports"_ property, then return **undefined**.
 > 1. If _pjson.name_ is equal to _packageName_, then
 >    1. If _packageSubpath_ is _undefined_, then
 >       1. Return the result of **PACKAGE_MAIN_RESOLVE**(_packageURL_, _pjson_).
@@ -1248,7 +1256,7 @@ _defaultEnv_ is the conditional environment name priority array,
 >             1. Return **PACKAGE_EXPORTS_RESOLVE**(_packageURL_, _subpath_,
 >                _pjson.exports_).
 >       1. Return the URL resolution of _subpath_ in _packageURL_.
-> 1. Otherwise return an empty result.
+> 1. Otherwise, return **undefined**.
 
 **PACKAGE_MAIN_RESOLVE**(_packageURL_, _pjson_)
 

doc/api/modules.md

@@ -160,9 +160,10 @@ require(X) from module at path Y
    a. LOAD_AS_FILE(Y + X)
    b. LOAD_AS_DIRECTORY(Y + X)
    c. THROW "not found"
-4. LOAD_NODE_MODULES(X, dirname(Y))
-5. LOAD_SELF_REFERENCE(X, dirname(Y))
-6. THROW "not found"
+4. LOAD_SELF_REFERENCE(X, dirname(Y), true)
+5. LOAD_NODE_MODULES(X, dirname(Y))
+6. LOAD_SELF_REFERENCE(X, dirname(Y), false)
+7. THROW "not found"
 
 LOAD_AS_FILE(X)
 1. If X is a file, load X as JavaScript text.  STOP
@@ -203,11 +204,12 @@ NODE_MODULES_PATHS(START)
    d. let I = I - 1
 5. return DIRS
 
-LOAD_SELF_REFERENCE(X, START)
+LOAD_SELF_REFERENCE(X, START, ENCAPSULATED)
 1. Find the closest package scope to START.
-2. If no scope was found, throw "not found".
-3. If the name in `package.json` isn't a prefix of X, throw "not found".
-4. Otherwise, resolve the remainder of X relative to this package as if it
+2. If no scope was found, return.
+3. If ENCAPSULATED is true and the `package.json` has no "exports", return.
+4. If the name in `package.json` isn't a prefix of X, throw "not found".
+5. Otherwise, resolve the remainder of X relative to this package as if it
    was loaded via `LOAD_NODE_MODULES` with a name in `package.json`.
 ```
 

lib/internal/modules/cjs/loader.js

@@ -431,13 +431,13 @@ function resolveBasePath(basePath, exts, isMain, trailingSlash, request) {
   return filename;
 }
 
-function trySelf(parentPath, isMain, request) {
+function trySelf(parentPath, isMain, request, encapsulated) {
   if (!experimentalSelf) {
     return false;
   }
 
   const { data: pkg, path: basePath } = readPackageScope(parentPath) || {};
-  if (!pkg) return false;
+  if (!pkg || (encapsulated && 'exports' in pkg === false)) return false;
   if (typeof pkg.name !== 'string') return false;
 
   let expansion;
@@ -1003,7 +1003,17 @@ Module._resolveFilename = function(request, parent, isMain, options) {
   }
 
   // Look up the filename first, since that's the cache key.
-  const filename = Module._findPath(request, paths, isMain);
+  if (parent && parent.filename) {
+    const filename = trySelf(parent.filename, isMain, request, true);
+    if (filename) {
+      emitExperimentalWarning('Package name self resolution');
+      const cacheKey = request + '\x00' +
+          (paths.length === 1 ? paths[0] : paths.join('\x00'));
+      Module._pathCache[cacheKey] = filename;
+      return filename;
+    }
+  }
+  const filename = Module._findPath(request, paths, isMain, false);
   if (filename) return filename;
   if (parent && parent.filename) {
     const filename = trySelf(parent.filename, isMain, request);

src/module_wrap.cc

@@ -1152,7 +1152,8 @@ Maybe<URL> PackageExportsResolve(Environment* env,
 Maybe<URL> ResolveSelf(Environment* env,
                        const std::string& pkg_name,
                        const std::string& pkg_subpath,
-                       const URL& base) {
+                       const URL& base,
+                       bool encapsulated) {
   if (!env->options()->experimental_resolve_self) {
     return Nothing<URL>();
   }
@@ -1172,6 +1173,7 @@ Maybe<URL> ResolveSelf(Environment* env,
       }
     }
     if (!found_pjson || pcfg->name != pkg_name) return Nothing<URL>();
+    if (encapsulated && pcfg->exports.IsEmpty()) return Nothing<URL>();
     if (!pkg_subpath.length()) {
       return PackageMainResolve(env, pjson_url, *pcfg, base);
     } else {
@@ -1227,7 +1229,7 @@ Maybe<URL> PackageResolve(Environment* env,
     pkg_subpath = "." + specifier.substr(sep_index);
   }
 
-  Maybe<URL> self_url = ResolveSelf(env, pkg_name, pkg_subpath, base);
+  Maybe<URL> self_url = ResolveSelf(env, pkg_name, pkg_subpath, base, true);
   if (self_url.IsJust()) {
     ProcessEmitExperimentalWarning(env, "Package name self resolution");
     return self_url;
@@ -1266,6 +1268,12 @@ Maybe<URL> PackageResolve(Environment* env,
     // Cross-platform root check.
   } while (pjson_path.length() != last_path.length());
 
+  self_url = ResolveSelf(env, pkg_name, pkg_subpath, base, false);
+  if (self_url.IsJust()) {
+    ProcessEmitExperimentalWarning(env, "Package name self resolution");
+    return self_url;
+  }
+
   std::string msg = "Cannot find package '" + pkg_name +
       "' imported from " + base.ToFilePath();
   node::THROW_ERR_MODULE_NOT_FOUND(env, msg.c_str());