Prevent multiple UNA segments in EDIFACT parsing

fixes #73

Author: nerdoc

pydifact/parser.py

@@ -22,6 +22,7 @@
 
 from collections.abc import Iterator
 
+from pydifact.exceptions import EDISyntaxError
 from pydifact.tokenizer import Tokenizer
 from pydifact.token import Token
 from pydifact.segments import Element, Elements, Segment, SegmentFactory
@@ -225,8 +226,11 @@ def convert_tokens_to_segments(
 
         for segment in segments:
             name = segment.pop(0)
+            if with_una and name == "UNA":
+                # we found another UNA segment.
+                # This is not in the specs, so raise an error
+                raise EDISyntaxError("There are not multiple UNA segments allowed.")
             if name == "UNB":
                 self.version = int(segment[0][1])
                 print("found edifact version", self.version)
             yield self.factory.create_segment(name, *segment, version=self.version)
-

tests/test_double_message.py

@@ -0,0 +1,16 @@
+import pytest
+
+from pydifact.exceptions import EDISyntaxError
+from pydifact.segmentcollection import Interchange
+from tests.test_input_output import path
+
+
+def test_message_with_2_UNA_segments():
+    with open(f"{path}/wikipedia_de.edi") as f:
+        content = f.read()
+
+    # doouble the message (2 UNA headers in one string!!)
+    content = content + content
+
+    with pytest.raises(EDISyntaxError):
+        Interchange.from_str(content)