converters/file: can now be used without being called

clize/converters.py

@@ -7,7 +7,9 @@
 import os
 from functools import partial
 
-from clize import parser, errors
+from sigtools.modifiers import autokwoargs
+
+from clize import parser, errors, util
 
 
 @parser.value_converter(name='TIME')
@@ -71,7 +73,10 @@ def _none_guard(cls, maybe_none, *args, **kwargs):
     else:
         return cls(maybe_none, *args, **kwargs)
 
-def file(stdio='-', keep_stdio_open=False, **kwargs):
+
+@parser.value_converter(name='FILE', convert_default=True)
+@autokwoargs(exceptions=['arg'])
+def file(arg=util.UNSET, stdio='-', keep_stdio_open=False, **kwargs):
     """Takes a file argument and provides a Python object that opens a file
 
     ::
@@ -101,11 +106,14 @@ def main(inf: file()='-'):
 
 
     """
+    if arg is not util.UNSET:
+        return _none_guard(_FileOpener, arg, kwargs, stdio, keep_stdio_open)
     return parser.value_converter(
         partial(_none_guard, _FileOpener, kwargs=kwargs,
                 stdio=stdio, keep_stdio_open=keep_stdio_open),
         name='FILE', convert_default=True)
 
+
 def _convert_ioerror(arg, exc):
     nexc = errors.ArgumentError('{0.strerror}: {1!r}'.format(exc, arg))
     nexc.__cause__ = exc

clize/tests/test_converters.py

@@ -72,6 +72,21 @@ def func(afile):
         self.assertFalse(e.getvalue())
         self.assertTrue(self.completed)
 
+    def test_not_called(self):
+        path = os.path.join(self.temp, 'afile')
+        open(path, 'w').close()
+        @modifiers.annotate(afile=converters.file)
+        def func(afile):
+            with afile as f:
+                self.assertEqual(f.name, path)
+                self.assertEqual(f.mode, 'r')
+            self.assertTrue(f.closed)
+            self.completed = True
+        o, e = self.crun(func, ['test', path])
+        self.assertFalse(o.getvalue())
+        self.assertFalse(e.getvalue())
+        self.assertTrue(self.completed)
+
     def test_file_write(self):
         path = os.path.join(self.temp, 'afile')
         @modifiers.annotate(afile=converters.file(mode='w'))