From 5b1cca92ab199798337d873f8a708df7acebe12a Mon Sep 17 00:00:00 2001
From: Florian Bruhin <git@the-compiler.org>
Date: Wed, 13 Jul 2016 13:46:47 +0200
Subject: [PATCH] Add run_js_blocking to tab API

---
 qutebrowser/browser/browsertab.py             |  8 ++++++++
 qutebrowser/browser/webengine/webenginetab.py | 15 +++++++++++++++
 qutebrowser/browser/webkit/webkittab.py       |  5 ++++-
 tests/unit/browser/test_tab.py                |  6 ++++++
 4 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/qutebrowser/browser/browsertab.py b/qutebrowser/browser/browsertab.py
index f034f4755..30979d255 100644
--- a/qutebrowser/browser/browsertab.py
+++ b/qutebrowser/browser/browsertab.py
@@ -611,6 +611,14 @@ class AbstractTab(QWidget):
         """
         raise NotImplementedError
 
+    def run_js_blocking(self, code):
+        """Run javascript and block.
+
+        This returns the result to the caller. Its use should be avoided when
+        possible as it runs a local event loop for QtWebEngine.
+        """
+        raise NotImplementedError
+
     def shutdown(self):
         raise NotImplementedError
 
diff --git a/qutebrowser/browser/webengine/webenginetab.py b/qutebrowser/browser/webengine/webenginetab.py
index 147f7be0f..c540f2f1d 100644
--- a/qutebrowser/browser/webengine/webenginetab.py
+++ b/qutebrowser/browser/webengine/webenginetab.py
@@ -343,6 +343,21 @@ class WebEngineTab(browsertab.AbstractTab):
         else:
             self._widget.page().runJavaScript(code, callback)
 
+    def run_js_blocking(self, code):
+        loop = qtutils.EventLoop()
+        js_ret = None
+
+        def js_cb(val):
+            nonlocal js_ret
+            js_ret = val
+            loop.quit()
+
+        self.run_js_async(code, js_cb)
+        loop.exec_()  # blocks until loop.quit() in js_cb
+        assert js_ret is not None
+
+        return js_ret
+
     def shutdown(self):
         log.stub()
 
diff --git a/qutebrowser/browser/webkit/webkittab.py b/qutebrowser/browser/webkit/webkittab.py
index 26a3dd663..f5ab2d7b9 100644
--- a/qutebrowser/browser/webkit/webkittab.py
+++ b/qutebrowser/browser/webkit/webkittab.py
@@ -525,10 +525,13 @@ class WebKitTab(browsertab.AbstractTab):
             callback(frame.toHtml())
 
     def run_js_async(self, code, callback=None):
-        result = self._widget.page().mainFrame().evaluateJavaScript(code)
+        result = self.run_js_blocking(code)
         if callback is not None:
             callback(result)
 
+    def run_js_blocking(self, code):
+        return self._widget.page().mainFrame().evaluateJavaScript(code)
+
     def icon(self):
         return self._widget.icon()
 
diff --git a/tests/unit/browser/test_tab.py b/tests/unit/browser/test_tab.py
index a4cc50c91..9500e7f39 100644
--- a/tests/unit/browser/test_tab.py
+++ b/tests/unit/browser/test_tab.py
@@ -121,6 +121,12 @@ def test_tab(qtbot, view, config_stub, tab_registry):
     assert view.parent() is tab_w
 
 
+class TestJs:
+
+    def test_blocking(self, tab):
+        assert tab.run_js_blocking('1 + 1') == 2
+
+
 class TestTabData:
 
     def test_known_attr(self):