repl: ensure eval serialization does not throw

If an error is thrown during the readline `keypress` event, the state of the streaming escape sequence decoder (added in #1601) will become corrupted. This will render the REPL (and possibly your whole terminal) completely unusable. This can be triggered by an object with a custom `inspect` method that throws. This commit adds an extra try/catch around `self.writer` (which is `util.inspect` by default).
nodejs · monsanto · Jun 13, 2015 · Jun 13, 2015 · Jun 13, 2015 · 2380c93a39e896da22992cf66acff9615ef592d8
commit 2380c93a39e896da22992cf66acff9615ef592d8
diff --git a/lib/repl.js b/lib/repl.js
@@ -344,7 +344,13 @@ function REPLServer(prompt,
       // If we got any output - print it (if no error)
       if (!e && (!self.ignoreUndefined || ret !== undefined)) {
         self.context._ = ret;
-        self.outputStream.write(self.writer(ret) + '\n');
+        try {
+          var s = self.writer(ret);
+        } catch(e) {
+          process.domain.emit('error', e);
+          return;
+        }
+        self.outputStream.write(s + '\n');
       }
 
       // Display prompt again

diff --git a/test/parallel/test-repl-inspect-throw.js b/test/parallel/test-repl-inspect-throw.js
@@ -0,0 +1,51 @@
+'use strict';
+var assert = require('assert');
+var common = require('../common');
+var util   = require('util');
+var repl   = require('repl');
+
+// A stream to push an array into a REPL
+function ArrayStream() {
+  this.run = function(data) {
+    var self = this;
+    data.forEach(function(line) {
+      self.emit('data', line + '\n');
+    });
+  };
+}
+util.inherits(ArrayStream, require('stream').Stream);
+ArrayStream.prototype.readable = true;
+ArrayStream.prototype.writable = true;
+ArrayStream.prototype.resume = function() {};
+ArrayStream.prototype.write = function() {};
+
+var putIn = new ArrayStream();
+var testMe = repl.start({
+  input: putIn,
+  output: putIn,
+  terminal: true
+});
+
+// Regression test: an exception raised during the 'keypress' event in readline
+// would corrupt the state of the escape sequence decoder, rendering the REPL
+// (and possibly your terminal) completely unusable.
+//
+// We can trigger this by triggering a throw inside util.inspect, which is used
+// to print a string representation of what you evaluate in the REPL.
+testMe.context.throwObj = {
+  inspect: function() {
+    throw new Error('inspect error');
+  }
+};
+testMe.context.reached = false;
+
+// Exceptions for whatever reason do not reach the normal error handler after
+// the inspect throw, but will work if run in another tick.
+process.nextTick(function() {
+  assert(testMe.context.reached);
+});
+
+putIn.run([
+  'throwObj',
+  'reached = true'
+]);