JS: improve NodeJSEventEmitter model

Author: esbena

Diff for: javascript/ql/src/semmle/javascript/frameworks/NodeJSLib.qll

@@ -783,7 +783,7 @@ module NodeJSLib {
   /**
    * A model of a URL request in the Node.js `http` library.
    */
-  private class NodeHttpUrlRequest extends NodeJSClientRequest::Range {
+  private class NodeHttpUrlRequest extends NodeJSClientRequest::Range, NodeJSEventEmitter {
     DataFlow::Node url;
 
     NodeHttpUrlRequest() {
@@ -1021,7 +1021,12 @@ module NodeJSLib {
   }
 
   private class ClientRequestEventEmitter extends NodeJSEventEmitter {
-    ClientRequestEventEmitter() { this = any(ClientRequestHandler handler).getAParameter() }
+    ClientRequestEventEmitter() {
+      exists(ClientRequestHandler handler |
+        not handler.getAHandledEvent() = "error" and
+        this = handler.getAParameter()
+      )
+    }
   }
 
   /**

Diff for: javascript/ql/test/library-tests/frameworks/EventEmitter/test.expected

@@ -22,7 +22,10 @@ eventEmitter
 | customEmitter.js:20:9:20:29 | new MyS ... itter() |
 | tst2.js:6:12:6:42 | new Con ... , opts) |
 | tst2.js:16:10:16:24 | new Connector() |
-| tst2.js:21:17:21:20 | data |
+| tst2.js:22:37:22:39 | res |
+| tst2.js:25:28:25:33 | socket |
+| tst2.js:29:37:29:39 | res |
+| tst2.js:32:28:32:33 | socket |
 | tst.js:3:10:3:22 | new emitter() |
 | tst.js:13:11:13:23 | new emitter() |
 | tst.js:18:11:18:23 | new emitter() |

Diff for: javascript/ql/test/library-tests/frameworks/EventEmitter/tst2.js

@@ -1,5 +1,5 @@
-var util = require('util');
-var EventEmitter = require('events').EventEmitter;
+var util = require("util");
+var EventEmitter = require("events").EventEmitter;
 
 var Connector = function() {
   if (!(this instanceof Connector)) {
@@ -17,5 +17,18 @@ var em = new Connector();
 em.on("foo", bar => {});
 em.emit("foo", "bar");
 
-var http = require('http');
-http.request(x, data => data.on("data", d => undefined ));
+var http = require("http");
+
+let req1 = http.request(x, function(res) {
+  res.on("data", function(data) {});
+});
+req1.on("socket", function(socket) {
+  socket.on("data", function(data) {});
+});
+
+let req2 = http.request(x, function(res) {
+  res.on("error", function(error) {});
+});
+req2.on("socket", function(socket) {
+  socket.on("error", function(error) {});
+});