tests/test_formdata.py

@@ -209,6 +209,11 @@ def test_file_field(pub, formdef):
     assert substvars.get('form_var_foo_url').endswith('/foobar/1/download?f=0')
     assert isinstance(substvars.get('form_var_foo_raw'), Upload)
 
+    pub.substitutions.feed(formdata)
+    context = pub.substitutions.get_context_variables(mode='lazy')
+    tmpl = Template('{{form_var_foo|length}}')
+    assert tmpl.render(context) == '8'
+
     formdata.data = {'0': None}
     substvars = formdata.get_substitution_variables()
     assert isinstance(substvars['form_var_foo'], NoneFieldVar)

wcs/variables.py

@@ -1605,6 +1605,9 @@ class LazyFieldVarFile(LazyFieldVar):
     def file_size(self):
         return self.raw.get_file_size() if self.raw else None
 
+    def __len__(self):
+        return len(self.raw.base_filename) if self.raw and self.raw.base_filename else 0
+
 
 class LazyBlockDataVar(LazyFormDataVar):
     def __init__(