configtypes: Allow completions for String.

qutebrowser/config/configtypes.py

@@ -236,10 +236,11 @@ class String(BaseType):
         minlen: Minimum length (inclusive).
         maxlen: Maximum length (inclusive).
         forbidden: Forbidden chars in the string.
+        _completions: completions to be used, or None
     """
 
     def __init__(self, minlen=None, maxlen=None, forbidden=None,
-                 none_ok=False):
+                 none_ok=False, completions=None):
         super().__init__(none_ok)
         if minlen is not None and minlen < 1:
             raise ValueError("minlen ({}) needs to be >= 1!".format(minlen))
@@ -251,6 +252,7 @@ class String(BaseType):
         self.minlen = minlen
         self.maxlen = maxlen
         self.forbidden = forbidden
+        self._completions = completions
 
     def validate(self, value):
         self._basic_validation(value)
@@ -267,6 +269,9 @@ class String(BaseType):
             raise configexc.ValidationError(value, "must be at most {} chars "
                                             "long!".format(self.maxlen))
 
+    def complete(self):
+        return self._completions
+
 
 class List(BaseType):
 

tests/unit/config/test_configtypes.py

@@ -334,6 +334,14 @@ class TestString:
     def test_transform(self, klass):
         assert klass().transform('foobar') == 'foobar'
 
+    @pytest.mark.parametrize('value', [
+        None,
+        ['one', 'two'],
+        [('1', 'one'), ('2', 'two')],
+    ])
+    def test_complete(self, klass, value):
+        assert klass(completions=value).complete() == value
+
 
 class TestList: