cmd: add a -i / --interactive flag to force the REPL

This is the only way to spawn a node child process in REPL mode, and will
also be needed to be able to use the REPL in MinTTY.

src/node.cc

@@ -111,6 +111,7 @@ static Persistent<String> emit_symbol;
 
 
 static bool print_eval = false;
+static bool force_repl = false;
 static char *eval_string = NULL;
 static int option_end_index = 0;
 static bool use_debug_agent = false;
@@ -2155,6 +2156,10 @@ Handle<Object> SetupProcessObject(int argc, char *argv[]) {
     process->Set(String::NewSymbol("_print_eval"), Boolean::New(print_eval));
   }
 
+  if (force_repl) {
+    process->Set(String::NewSymbol("_forceRepl"), True());
+  }
+
   size_t size = 2*PATH_MAX;
   char* execPath = new char[size];
   if (uv_exepath(execPath, &size) != 0) {
@@ -2299,6 +2304,8 @@ static void PrintHelp() {
          "  -v, --version        print node's version\n"
          "  -e, --eval script    evaluate script\n"
          "  -p, --print          print result of --eval\n"
+         "  -i, --interactive    always enter the REPL even if stdin\n"
+         "                       does not appear to be a terminal\n"
          "  --v8-options         print v8 command line options\n"
          "  --vars               print various compiled-in variables\n"
          "  --max-stack-size=val set max v8 stack size (bytes)\n"
@@ -2360,6 +2367,9 @@ static void ParseArgs(int argc, char **argv) {
     } else if (strcmp(arg, "--print") == 0 || strcmp(arg, "-p") == 0) {
       print_eval = true;
       argv[i] = const_cast<char*>("");
+    } else if (strcmp(arg, "--interactive") == 0 || strcmp(arg, "-i") == 0) {
+      force_repl = true;
+      argv[i] = const_cast<char*>("");
     } else if (strcmp(arg, "--v8-options") == 0) {
       argv[i] = const_cast<char*>("--help");
     } else if (argv[i][0] != '-') {

src/node.js

@@ -118,8 +118,8 @@
     } else {
       var Module = NativeModule.require('module');
 
-      // If stdin is a TTY.
-      if (NativeModule.require('tty').isatty(0)) {
+      // If -i or --interactive were passed, or stdin is a TTY.
+      if (process._forceRepl || NativeModule.require('tty').isatty(0)) {
         // REPL
         var repl = Module.requireRepl().start('> ', null, null, true);
         repl.on('exit', function() {

test/simple/test-force-repl.js

@@ -0,0 +1,44 @@
+// Copyright Joyent, Inc. and other Node contributors.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+var common = require('../common');
+var assert = require('assert');
+var spawn = require('child_process').spawn;
+
+// spawn a node child process in "interactive" mode (force the repl)
+var cp = spawn(process.execPath, ['-i']);
+var gotToEnd = false;
+var timeoutId = setTimeout(function() {
+  throw new Error('timeout!');
+}, 1000); // give node + the repl 1 second to boot up
+
+cp.stdout.setEncoding('utf8');
+
+cp.stdout.once('data', function(b) {
+  clearTimeout(timeoutId);
+  assert.equal(b, '> ');
+  gotToEnd = true;
+  cp.kill();
+});
+
+process.on('exit', function() {
+  assert(gotToEnd);
+});