repl: break on sigint/ctrl+c

Adds the ability to stop execution of the current REPL command
when receiving SIGINT. This applies only to the default eval
function.

Fixes: https://github.com/nodejs/node/issues/6612
PR-URL: https://github.com/nodejs/node/pull/6635
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

2 files changed, 48 insertions, 6 deletions

diff --git a/lib/internal/repl.js b/lib/internal/repl.js
index b72741609b..dd14f42fa5 100644
--- a/lib/internal/repl.js
+++ b/lib/internal/repl.js
@@ -22,7 +22,8 @@ function createRepl(env, opts, cb) {
   opts = opts || {
     ignoreUndefined: false,
     terminal: process.stdout.isTTY,
-    useGlobal: true
+    useGlobal: true,
+    breakEvalOnSigint: true
   };
 
   if (parseInt(env.NODE_NO_READLINE)) {
diff --git a/lib/repl.js b/lib/repl.js
index 387e3b5446..db5754ec04 100644
--- a/lib/repl.js
+++ b/lib/repl.js
@@ -24,6 +24,7 @@
 const internalModule = require('internal/module');
 const internalUtil = require('internal/util');
 const util = require('util');
+const utilBinding = process.binding('util');
 const inherits = util.inherits;
 const Stream = require('stream');
 const vm = require('vm');
@@ -178,7 +179,7 @@ function REPLServer(prompt,
                           replMode);
   }
 
-  var options, input, output, dom;
+  var options, input, output, dom, breakEvalOnSigint;
   if (prompt !== null && typeof prompt === 'object') {
     // an options object was given
     options = prompt;
@@ -191,10 +192,17 @@ function REPLServer(prompt,
     prompt = options.prompt;
     dom = options.domain;
     replMode = options.replMode;
+    breakEvalOnSigint = options.breakEvalOnSigint;
   } else {
     options = {};
   }
 
+  if (breakEvalOnSigint && eval_) {
+    // Allowing this would not reflect user expectations.
+    // breakEvalOnSigint affects only the behaviour of the default eval().
+    throw new Error('Cannot specify both breakEvalOnSigint and eval for REPL');
+  }
+
   var self = this;
 
   self._domain = dom || domain.create();
@@ -204,6 +212,7 @@ function REPLServer(prompt,
   self.replMode = replMode || exports.REPL_MODE_SLOPPY;
   self.underscoreAssigned = false;
   self.last = undefined;
+  self.breakEvalOnSigint = !!breakEvalOnSigint;
 
   self._inTemplateLiteral = false;
 
@@ -267,14 +276,46 @@ function REPLServer(prompt,
     regExMatcher.test(savedRegExMatches.join(sep));
 
     if (!err) {
+      // Unset raw mode during evaluation so that Ctrl+C raises a signal.
+      let previouslyInRawMode;
+      if (self.breakEvalOnSigint) {
+        // 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();
+        previouslyInRawMode = self._setRawMode(false);
+      }
+
       try {
-        if (self.useGlobal) {
-          result = script.runInThisContext({ displayErrors: false });
-        } else {
-          result = script.runInContext(context, { displayErrors: false });
+        try {
+          const scriptOptions = {
+            displayErrors: false,
+            breakOnSigint: self.breakEvalOnSigint
+          };
+
+          if (self.useGlobal) {
+            result = script.runInThisContext(scriptOptions);
+          } else {
+            result = script.runInContext(context, scriptOptions);
+          }
+        } finally {
+          if (self.breakEvalOnSigint) {
+            // Reset terminal mode to its previous value.
+            self._setRawMode(previouslyInRawMode);
+
+            // Returns true if there were pending SIGINTs *after* the script
+            // has terminated without being interrupted itself.
+            if (utilBinding.stopSigintWatchdog()) {
+              self.emit('SIGINT');
+            }
+          }
         }
       } catch (e) {
         err = e;
+        if (err.message === 'Script execution interrupted.') {
+          // The stack trace for this case is not very useful anyway.
+          Object.defineProperty(err, 'stack', { value: '' });
+        }
+
         if (err && process.domain) {
           debug('not recoverable, send to domain');
           process.domain.emit('error', err);