Add cmdutils.arg_or_count

TODO

@@ -94,7 +94,6 @@ Style
 =====
 
 - initialize completion models at some nicer place (not in widget)
-- add util function to check arg/count
 - move curcommand stuff to other places (e.g. current widget, etc.)
   maybe rename curcommand to commands or so?
   also some curcommand stuff is in tabbedbrowser, etc.

qutebrowser/browser/curcommand.py

@@ -406,19 +406,10 @@ class CurCommandDispatcher(QObject):
         Args:
             count: How many steps to take.
         """
-        if zoom is not None and count is not None:
-            message.error("Either argument or count must be given!")
-            return
-        if zoom is not None:
-            try:
-                level = int(zoom)
-            except ValueError:
-                message.error("Argument {} must be an integer!".format(zoom))
-                return
-        elif count is not None:
-            level = count
-        else:
-            level = 100
+        try:
+            level = cmdutils.arg_or_count(zoom, count, default=100)
+        except ValueError as e:
+            message.error(e)
         tab = self._tabs.currentWidget()
         tab.zoom_perc(level)
 

qutebrowser/commands/utils.py

@@ -29,6 +29,44 @@ from qutebrowser.commands._command import Command
 cmd_dict = {}
 
 
+def arg_or_count(arg, count, default=None, countzero=None):
+
+    """Get a value based on an argument and count given to a command.
+
+    If both arg and count are set, ValueError is raised.
+    If only arg/count is set, it is used.
+    If none is set, a default is returned or ValueError is raised.
+
+    Args:
+        arg: The argument given to a command.
+        count: The count given to a command.
+        countzero: Special value if count is 0.
+
+    Return:
+        The value to use.
+
+    Raise:
+        ValueError: If nothing was set or the value couldn't be converted to
+                    an integer.
+    """
+    if count is not None and arg is not None:
+        raise ValueError("Both count and argument given!")
+    elif arg is not None:
+        try:
+            return int(arg)
+        except ValueError:
+            raise ValueError("Invalid number: {}".format(arg))
+    elif count is not None:
+        if countzero is not None and count == 0:
+            return countzero
+        else:
+            return int(count)
+    elif default is not None:
+        return int(default)
+    else:
+        raise ValueError("Either count or argument have to be set!")
+
+
 class register:  # pylint: disable=invalid-name
 
     """Decorator to register a new command handler.

qutebrowser/widgets/_tabbedbrowser.py

@@ -400,23 +400,12 @@ class TabbedBrowser(TabWidget):
         Args:
             index: The tab index to focus, starting with 1.
         """
-        if index is not None and count is not None:
-            message.error("Either argument or count must be given!")
+        try:
+            idx = cmdutils.arg_or_count(index, count, default=1,
+                                        countzero=self.count())
+        except ValueError as e:
+            message.error(e)
             return
-        elif index is not None:
-            try:
-                idx = int(index)
-            except ValueError:
-                message.error("Argument ({}) needs to be a number!".format(
-                    index))
-                return
-        elif count is not None:
-            if count == 0:
-                idx = self.count()
-            else:
-                idx = count
-        else:
-            idx = 1
         if 1 <= idx <= self.count():
             self.setCurrentIndex(idx - 1)
         else: