repl: fix tab completion for a non-global context

Use vm.isContext() to properly identify contexts.

PR-URL: https://github.com/joyent/node/pull/25382
PR-URL: https://github.com/nodejs/io.js/pull/2052
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

lib/repl.js

@@ -611,9 +611,7 @@ REPLServer.prototype.complete = function(line, callback) {
       if (!expr) {
         // If context is instance of vm.ScriptContext
         // Get global vars synchronously
-        if (this.useGlobal ||
+        if (this.useGlobal || vm.isContext(this.context)) {
-            this.context.constructor &&
-            this.context.constructor.name === 'Context') {
           var contextProto = this.context;
           while (contextProto = Object.getPrototypeOf(contextProto)) {
             completionGroups.push(Object.getOwnPropertyNames(contextProto));

test/parallel/test-repl-tab-complete.js

@@ -206,3 +206,13 @@ testMe.complete('require(\'n', function(error, data) {
   assert.strictEqual(error, null);
   assert.deepEqual(data, [['net'], 'n']);
 });
+
+// Make sure tab completion works on context properties
+putIn.run(['.clear']);
+
+putIn.run([
+  'var custom = "test";'
+]);
+testMe.complete('cus', function(error, data) {
+  assert.deepEqual(data, [['custom'], 'cus']);
+});