repl: fix _debugger by properly proxying repl

The _debugger module uses the internal REPL module, but expects
to receive the userland REPL module. This fixes the breakage that
occurs by proxying the userland REPL module through the internal
module.

It also fixes an unintended in-REPL bug, where require(node-module)
was not resolving correctly.

PR-URL: #1605
Reviewed-By: Roman Reiss <me@silverwind.io>

lib/internal/repl.js

@@ -1,29 +1,22 @@
 'use strict';
 
-module.exports = {createRepl: createRepl};
-
 const Interface = require('readline').Interface;
 const REPL = require('repl');
 const path = require('path');
 
+module.exports = Object.create(REPL);
+module.exports.createInternalRepl = createRepl;
+
 // XXX(chrisdickinson): The 15ms debounce value is somewhat arbitrary.
 // The debounce is to guard against code pasted into the REPL.
 const kDebounceHistoryMS = 15;
 
-try {
-  // hack for require.resolve("./relative") to work properly.
-  module.filename = path.resolve('repl');
-} catch (e) {
-  // path.resolve('repl') fails when the current working directory has been
-  // deleted.  Fall back to the directory name of the (absolute) executable
-  // path.  It's not really correct but what are the alternatives?
-  const dirname = path.dirname(process.execPath);
-  module.filename = path.resolve(dirname, 'repl');
+// XXX(chrisdickinson): hack to make sure that the internal debugger
+// uses the original repl.
+function replStart() {
+  return REPL.start.apply(REPL, arguments);
 }
 
-// hack for repl require to work properly with node_modules folders
-module.paths = require('module')._nodeModulePaths(module.filename);
-
 function createRepl(env, cb) {
   const opts = {
     ignoreUndefined: false,

lib/repl.js

@@ -32,6 +32,20 @@ const Console = require('console').Console;
 const domain = require('domain');
 const debug = util.debuglog('repl');
 
+try {
+  // hack for require.resolve("./relative") to work properly.
+  module.filename = path.resolve('repl');
+} catch (e) {
+  // path.resolve('repl') fails when the current working directory has been
+  // deleted.  Fall back to the directory name of the (absolute) executable
+  // path.  It's not really correct but what are the alternatives?
+  const dirname = path.dirname(process.execPath);
+  module.filename = path.resolve(dirname, 'repl');
+}
+
+// hack for repl require to work properly with node_modules folders
+module.paths = require('module')._nodeModulePaths(module.filename);
+
 // If obj.hasOwnProperty has been overridden, then calling
 // obj.hasOwnProperty(prop) will break.
 // See: https://github.com/joyent/node/issues/1707

src/node.js

@@ -130,7 +130,7 @@
         // If -i or --interactive were passed, or stdin is a TTY.
         if (process._forceRepl || NativeModule.require('tty').isatty(0)) {
           // REPL
-          Module.requireRepl().createRepl(process.env, function(err, repl) {
+          Module.requireRepl().createInternalRepl(process.env, function(err, repl) {
             if (err) {
               throw err;
             }