repl: disable Ctrl+C support on win32 for now

Disable Windows support for interrupting REPL commands using
Ctrl+C by default, because the switches from console raw mode
and back have been interfering with printing the results of
evaluated expressions.

This is a temporary measure, since the underlying problem is
very likely not related to this specific feature.

Ref: #7837

PR-URL: #7977
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Nikolai Vavilov <vvnicholas@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: João Reis <reis@janeasystems.com>

Author: addaleax

lib/repl.js

@@ -289,7 +289,13 @@ function REPLServer(prompt,
     if (!err) {
       // Unset raw mode during evaluation so that Ctrl+C raises a signal.
       let previouslyInRawMode;
-      if (self.breakEvalOnSigint) {
+
+      // Temporarily disabled on Windows due to output problems that likely
+      // result from the raw mode switches here, see
+      // https://github.com/nodejs/node/issues/7837
+      // Setting NODE_REPL_CTRLC is meant as a temporary opt-in for debugging.
+      if (self.breakEvalOnSigint &&
+          (process.platform !== 'win32' || process.env.NODE_REPL_CTRLC)) {
         // Start the SIGINT watchdog before entering raw mode so that a very
         // quick Ctrl+C doesn’t lead to aborting the process completely.
         utilBinding.startSigintWatchdog();
@@ -309,7 +315,8 @@ function REPLServer(prompt,
             result = script.runInContext(context, scriptOptions);
           }
         } finally {
-          if (self.breakEvalOnSigint) {
+          if (self.breakEvalOnSigint &&
+              (process.platform !== 'win32' || process.env.NODE_REPL_CTRLC)) {
             // Reset terminal mode to its previous value.
             self._setRawMode(previouslyInRawMode);