Merge branch 'jseval' of https://github.com/Carpetsmoker/qutebrowser into Carpetsmoker-jseval

doc/help/commands.asciidoc

@@ -20,6 +20,7 @@
 |<<hint,hint>>|Start hinting.
 |<<home,home>>|Open main startpage in current tab.
 |<<inspector,inspector>>|Toggle the web inspector.
+|<<jseval,jseval>>|Evaluate a JavaScript string.
 |<<later,later>>|Execute a command after some time.
 |<<navigate,navigate>>|Open typical prev/next links or navigate using the URL path.
 |<<open,open>>|Open a URL in the current/[count]th tab.
@@ -241,6 +242,19 @@ Open main startpage in current tab.
 === inspector
 Toggle the web inspector.
 
+[[jseval]]
+=== jseval
+Syntax: +:jseval 'js_code'+
+
+Evaluate a JavaScript string.
+
+==== positional arguments
+* +'js_code'+: The string to evaluate.
+
+==== note
+* This command does not split arguments after the last argument and handles quotes literally.
+* With this command, +;;+ is interpreted literally instead of splitting off a second command.
+
 [[later]]
 === later
 Syntax: +:later 'ms' 'command'+

qutebrowser/browser/commands.py

@@ -1563,3 +1563,29 @@ class CommandDispatcher:
         view = self._current_widget()
         for _ in range(count):
             view.triggerPageAction(member)
+
+    @cmdutils.register(instance='command-dispatcher', scope='window',
+                       maxsplit=0, no_cmd_split=True)
+    def jseval(self, js_code):
+        """Evaluate a JavaScript string.
+
+        Args:
+            js_code: The string to evaluate.
+        """
+        out = self._current_widget().page().mainFrame().evaluateJavaScript(
+                    js_code)
+
+        if out is None:
+            # Getting the actual error (if any) seems to be difficult. The
+            # error does end up in BrowserPage.javaScriptConsoleMessage(), but
+            # distinguishing between :jseval errors and errors from the webpage
+            # is not trivial...
+            message.info(self._win_id, 'No output or error')
+        else:
+            # The output can be a string, number, dict, array, etc. But *don't*
+            # output too much data, as this will make qutebrowser hang
+            out = str(out)
+            if len(out) > 5000:
+                message.info(self._win_id, out[:5000] + ' [...trimmed...]')
+            else:
+                message.info(self._win_id, out)