forms: factor out file attachment lookup (#8031)

wcs/forms/common.py

@@ -32,13 +32,26 @@ from qommon import errors
 
 class FileDirectory(Directory):
     _q_exports = []
+    _lookup_methods = ['lookup_file_field']
 
-    def __init__(self, formdata, field_no):
+    def __init__(self, formdata, reference):
         self.formdata = formdata
-        self.field_no = field_no
+        self.reference = reference
+
+    def lookup_file_field(self, filename):
+        if self.reference in self.formdata.data:
+            return self.formdata.data[self.reference]
 
     def _q_lookup(self, component):
-        file = self.formdata.data[self.field_no]
+        upload = None
+        for lookup_method_name in self._lookup_methods:
+            lookup_method = getattr(self, lookup_method_name)
+            file = lookup_method(filename=component)
+            if file:
+                break
+        else:
+            # no such file
+            raise errors.TraversalError()
 
         if component and component != file.base_filename:
             raise errors.TraversalError()
@@ -67,7 +80,7 @@ class FilesDirectory(Directory):
         self.formdata = formdata
 
     def _q_lookup(self, component):
-        return FileDirectory(self.formdata, component)
+        return FileDirectory(self.formdata, reference=component)
 
 
 class FormStatusPage(Directory):