Only allow xdebug to handle exceptions when request comes through ind…

…ex.php

- Since the Bootstrap::run method is called from files like get.php and
  static.php, it is important that exceptions result in 404 headers,
  even when in developer mode.

index.php

@@ -36,4 +36,4 @@
 $bootstrap = \Magento\Framework\App\Bootstrap::create(BP, $_SERVER);
 /** @var \Magento\Framework\App\Http $app */
 $app = $bootstrap->createApplication('Magento\Framework\App\Http');
-$bootstrap->run($app);
+$bootstrap->run($app, false);

lib/internal/Magento/Framework/App/Bootstrap.php

@@ -244,17 +244,23 @@ public function createApplication($type, $arguments = [])
      * Runs an application
      *
      * @param \Magento\Framework\AppInterface $application
+     * @param bool $alwaysHandleExceptions Whether to handle exceptions regardless of developer mode setting
      * @return void
      */
-    public function run(AppInterface $application)
+    public function run(AppInterface $application, $alwaysHandleExceptions = true)
     {
         $prelaunchSuccessful = $this->preLaunch($application);
         if (!$prelaunchSuccessful) {
             return;
         }
 
         // If ignoring exceptions, don't wrap in a try/catch block so that PHP/Xdebug can output a clean backtrace
-        if ($this->isDeveloperMode() && $this->ignoreExceptionsInDeveloperMode()) {
+        if ($this->isDeveloperMode()
+            && $this->ignoreExceptionsInDeveloperMode()
+            // Certain entry points such as get.php and static.php should always be handled by the try/catch block
+            // below since any exceptions should return a 404 header
+            && !$alwaysHandleExceptions
+        ) {
             Profiler::start('magento');
             $response = $application->launch();
             $response->sendResponse();

pub/index.php

@@ -34,4 +34,4 @@
 $bootstrap = \Magento\Framework\App\Bootstrap::create(BP, $params);
 /** @var \Magento\Framework\App\Http $app */
 $app = $bootstrap->createApplication('Magento\Framework\App\Http');
-$bootstrap->run($app);
+$bootstrap->run($app, false);