Add a cmdutils.check_exclusive function.

qutebrowser/browser/commands.py

@@ -115,9 +115,8 @@ class CommandDispatcher:
                 errstr += " - {}".format(url.errorString())
             raise cmdexc.CommandError(errstr)
         tabbed_browser = self._tabbed_browser()
-        if sum(1 for e in (tab, background, window) if e) > 1:
-            raise cmdexc.CommandError("Only one of -t/-b/-w can be given!")
-        elif window:
+        cmdutils.check_exclusive((tab, background, window), 'tbw')
+        if window:
             tabbed_browser = self._tabbed_browser(window=True)
             tabbed_browser.tabopen(url)
         elif tab:
@@ -229,8 +228,7 @@ class CommandDispatcher:
             QTabBar.SelectLeftTab, QTabBar.SelectRightTab, or None if no change
             should be made.
         """
-        if sum(1 for e in (left, right, opposite) if e) > 1:
-            raise cmdexc.CommandError("Only one of -l/-r/-o can be given!")
+        cmdutils.check_exclusive((left, right, opposite), 'lro')
         if left:
             return QTabBar.SelectLeftTab
         elif right:
@@ -488,8 +486,7 @@ class CommandDispatcher:
             bg: Open in a background tab.
             window: Open in a new window.
         """
-        if sum(1 for e in (tab, bg, window) if e) > 1:
-            raise cmdexc.CommandError("Only one of -t/-b/-w can be given!")
+        cmdutils.check_exclusive((tab, bg, window), 'tbw')
         widget = self._current_widget()
         frame = widget.page().currentFrame()
         url = self._current_url()

qutebrowser/commands/cmdutils.py

@@ -82,6 +82,21 @@ def arg_or_count(arg, count, default=None, countzero=None):
         raise ValueError("Either count or argument have to be set!")
 
 
+def check_exclusive(flags, names):
+    """Check if only one flag is set with exclusive flags.
+
+    Raise a CommandError if not.
+
+    Args:
+        flags: An iterable of booleans to check.
+        names: An iterable of flag names for the error message.
+    """
+    if sum(1 for e in flags if e) > 1:
+        argstr = '/'.join('-' + e for e in names)
+        raise cmdexc.CommandError("Only one of {} can be given!".format(
+            argstr))
+
+
 class register:  # pylint: disable=invalid-name
 
     """Decorator to register a new command handler.