From 20607dfab0cd86442a53353dd4680ab0639a11aa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Gina=20H=C3=A4u=C3=9Fge?= <osd@foosel.net>
Date: Wed, 31 Aug 2016 15:50:33 +0200
Subject: [PATCH] Work around a race condition(?) causing issues on startup

See lengthy comment inside main.js added in this commit.
---
 src/octoprint/static/js/app/main.js               | 15 ++++++++++++++-
 .../static/js/app/viewmodels/settings.js          |  6 +++---
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/src/octoprint/static/js/app/main.js b/src/octoprint/static/js/app/main.js
index d21cdd5f..0d116502 100644
--- a/src/octoprint/static/js/app/main.js
+++ b/src/octoprint/static/js/app/main.js
@@ -558,7 +558,20 @@ $(function() {
                 callViewModels(allViewModels, "onStartup");
 
                 viewModelMap["settingsViewModel"].requestData()
-                    .done(bindViewModels);
+                    .done(function() {
+                        // There appears to be an odd race condition either in JQuery's AJAX implementation or
+                        // the browser's implementation of XHR, causing a second GET request from inside the
+                        // completion handler of the very same request to never get its completion handler called
+                        // if ETag headers are present on the response (the status code of the request does NOT
+                        // seem to matter here, only that the ETag header is present).
+                        //
+                        // Minimal example with which I was able to reproduce this behaviour can be found
+                        // at https://gist.github.com/foosel/b2ddb9ebd71b0b63a749444651bfce3f
+                        //
+                        // Decoupling all consecutive calls from this done event handler hence is an easy way
+                        // to avoid this problem. A zero timeout should do the trick nicely.
+                        window.setTimeout(bindViewModels, 0);
+                    });
             });
     }
 );
diff --git a/src/octoprint/static/js/app/viewmodels/settings.js b/src/octoprint/static/js/app/viewmodels/settings.js
index 3a91f120..a1be680a 100644
--- a/src/octoprint/static/js/app/viewmodels/settings.js
+++ b/src/octoprint/static/js/app/viewmodels/settings.js
@@ -460,6 +460,9 @@ $(function() {
             // perform the request
             self.receiving(true);
             return OctoPrint.settings.get()
+                .always(function() {
+                    self.receiving(false);
+                })
                 .done(function(response) {
                     self.fromResponse(response, local);
 
@@ -483,9 +486,6 @@ $(function() {
                         deferred.reject(args);
                     });
                     self.outstanding = [];
-                })
-                .always(function() {
-                    self.receiving(false);
                 });
         };