feat: send 500s for unhandled requests

lib/server.js

@@ -1352,7 +1352,10 @@ Server.prototype._finishReqResCycle = function _finishReqResCycle(
     var self = this;
     var route = req.route; // can be undefined when 404 or error
 
-    if (res._finished) {
+    // if the returned err value was a string, then we're handling the
+    // next('foo') case where we redirect to another middleware stack. don't
+    // do anything here because we're not done yet.
+    if (res._finished || _.isString(err)) {
         return;
     }
 
@@ -1366,6 +1369,22 @@ Server.prototype._finishReqResCycle = function _finishReqResCycle(
         var finalErr = err || res.err;
         req.emit('restifyDone', route, finalErr);
         self.emit('after', req, res, route, finalErr);
+    } else if (
+        res._handlersFinished === true &&
+        res.headersSent === false &&
+        !res.err
+    ) {
+        // if we reached the end of the handler chain and headers haven't been
+        // sent AND there isn't an existing res.err (e.g., req abort/close),
+        // it's possible it's a user error and a response was never written.
+        // send a 500.
+        res.send(
+            new errors.InternalServerError(
+                'reached the end of the handler chain without ' +
+                    'writing a response!'
+            )
+        );
+        return;
     } else {
         // Store error for when the response is flushed and we actually emit the
         // 'after' event. The "err" object passed to this method takes

test/server.test.js

@@ -2497,6 +2497,48 @@ test('should emit error with multiple next calls with strictNext', function(t) {
     });
 });
 
+test(
+    'should send 500 if we reached the end of handler chain w/o sending ' +
+        'headers',
+    function(t) {
+        var server = restify.createServer({
+            dtrace: helper.dtrace,
+            strictNext: true,
+            log: helper.getLog('server')
+        });
+        var client;
+        var port;
+
+        server.listen(PORT + 1, '127.0.0.1', function() {
+            port = server.address().port;
+            client = restifyClients.createJsonClient({
+                url: 'http://127.0.0.1:' + port,
+                dtrace: helper.dtrace,
+                retry: false
+            });
+
+            server.get('/noResponse', function(req, res, next) {
+                next();
+            });
+
+            client.get('/noResponse', function(err, _, res) {
+                t.ok(err);
+                t.equal(res.statusCode, 500);
+                t.equal(err.name, 'InternalServerError');
+                t.equal(
+                    err.message,
+                    'reached the end of the handler chain without ' +
+                        'writing a response!'
+                );
+                client.close();
+                server.close(function() {
+                    t.end();
+                });
+            });
+        });
+    }
+);
+
 test('uncaughtException should not trigger named routeHandler', function(t) {
     SERVER.get(
         {