Node CJS module resolver hooks

node.diff

diff --git a/lib/internal/modules/cjs/loader.js b/lib/internal/modules/cjs/loader.js
index 33d8907e4f..6df7c32efd 100644
--- a/lib/internal/modules/cjs/loader.js
+++ b/lib/internal/modules/cjs/loader.js
@@ -46,6 +46,9 @@ const preserveSymlinks = !!process.binding('config').preserveSymlinks;
 const preserveSymlinksMain = !!process.binding('config').preserveSymlinksMain;
 const experimentalModules = !!process.binding('config').experimentalModules;

+const { defineProperties, hasOwnProperty } = Object;
+const { apply } = Reflect;
+
 const {
   ERR_INVALID_ARG_TYPE,
   ERR_INVALID_ARG_VALUE,
@@ -628,6 +631,8 @@ Module.prototype.load = function(filename) {
 };


+var requireModuleHook;
+
 // Loads a module at the given file path. Returns that module's
 // `exports` property.
 Module.prototype.require = function(id) {
@@ -638,6 +643,33 @@ Module.prototype.require = function(id) {
     throw new ERR_INVALID_ARG_VALUE('id', id,
                                     'must be a non-empty string');
   }
+
+  if (requireModuleHook === undefined) {  // On first module load.
+    requireModuleHook = null;  // Do not invoke bootstrap to find the hook.
+    var hookid = process.binding('config').cjsUserLoader;
+    if (hookid && typeof hookid === 'string') {
+      var hook = this.require(hookid);
+      if (typeof hook === 'function') {
+        requireModuleHook = hook;
+      }
+    }
+  }
+
+  if (typeof requireModuleHook === 'function') {
+    var isBuiltin = apply(hasOwnProperty, NativeModule._source, [id]);
+    id = requireModuleHook(
+      this.filename, this.id, id,
+      (req, opts) => Module._resolveFilename(req, this, false, opts),
+      isBuiltin);
+
+    if (typeof id !== 'string') {
+      throw new ERR_INVALID_ARG_TYPE('id', 'string', id);
+    }
+    if (id === '') {
+      throw new ERR_INVALID_ARG_VALUE('id', id, 'must be a non-empty string');
+    }
+  }
+
   return Module._load(id, this, /* isMain */ false);
 };

diff --git a/src/node.cc b/src/node.cc
index 71b130a63f..efd683dc64 100644
--- a/src/node.cc
+++ b/src/node.cc
@@ -262,6 +262,11 @@ bool config_experimental_repl_await = false;
 // that is used by lib/internal/bootstrap/node.js
 std::string config_userland_loader;  // NOLINT(runtime/string)

+// Set in node.cc by ParseArgs when --cjs-loader is used.
+// Used in node_config.cc to set a constant on process.binding('config')
+// that is used by lib/internal/bootstrap/node.js
+std::string config_cjs_userland_loader;  // NOLINT(runtime/string)
+
 // Set by ParseArgs when --pending-deprecation or NODE_PENDING_DEPRECATION
 // is used.
 bool config_pending_deprecation = false;
@@ -3656,6 +3661,7 @@ static void CheckIfAllowedInEnv(const char* exe, bool is_env,

   static const char* whitelist[] = {
     // Node options, sorted in `node --help` order for ease of comparison.
+    "--cjs-loader",
     "--enable-fips",
     "--experimental-modules",
     "--experimental-repl-await",
@@ -3873,6 +3879,14 @@ static void ParseArgs(int* argc,
       }
       args_consumed += 1;
       config_userland_loader = module;
+    } else if (strcmp(arg, "--cjs-loader") == 0) {
+      const char* module = argv[index + 1];
+      if (module == nullptr) {
+        fprintf(stderr, "%s: %s requires an argument\n", argv[0], arg);
+        exit(9);
+      }
+      args_consumed += 1;
+      config_cjs_userland_loader = module;
     } else if (strcmp(arg, "--prof-process") == 0) {
       prof_process = true;
       short_circuit = true;
diff --git a/src/node_config.cc b/src/node_config.cc
index 603d55491a..2bc9d7af69 100644
--- a/src/node_config.cc
+++ b/src/node_config.cc
@@ -88,6 +88,16 @@ static void Initialize(Local<Object> target,
     }
   }

+  if (!config_cjs_userland_loader.empty()) {
+    target->DefineOwnProperty(
+        context,
+        FIXED_ONE_BYTE_STRING(isolate, "cjsUserLoader"),
+        String::NewFromUtf8(isolate,
+                            config_cjs_userland_loader.data(),
+                            v8::NewStringType::kNormal).ToLocalChecked(),
+        ReadOnly).FromJust();
+  }
+
   if (config_experimental_vm_modules)
     READONLY_BOOLEAN_PROPERTY("experimentalVMModules");

diff --git a/src/node_internals.h b/src/node_internals.h
index 1ba56458b1..e0c43e4bfa 100644
--- a/src/node_internals.h
+++ b/src/node_internals.h
@@ -198,6 +198,11 @@ extern bool config_experimental_repl_await;
 // that is used by lib/internal/bootstrap/node.js
 extern std::string config_userland_loader;

+// Set in node.cc by ParseArgs when --cjs-loader is used.
+// Used in node_config.cc to set a constant on process.binding('config')
+// that is used by lib/internal/bootstrap/node.js
+extern std::string config_cjs_userland_loader;
+
 // Set in node.cc by ParseArgs when --expose-internals or --expose_internals is
 // used.
 // Used in node_config.cc to set a constant on process.binding('config')