Fix parsing empty attribute groups (#650)

Author: ciphax

src/pyipp/parser.py

@@ -289,26 +289,28 @@ def parse(  # noqa: PLR0912, PLR0915
 
             attribute_key = "unsupported-attributes"
             offset += 1
+        else:
+            attribute, new_offset = parse_attribute(
+                raw_data,
+                offset,
+                previous_attribute_name,
+            )
 
-        attribute, new_offset = parse_attribute(
-            raw_data, offset, previous_attribute_name,
-        )
-
-        # if attribute has a name -> add it
-        # if attribute doesn't have a name -> it is part of an array
-        if attribute["name"]:
-            tmp_data[attribute["name"]] = attribute["value"]
-            previous_attribute_name = attribute["name"]
-        elif previous_attribute_name:
-            # check if attribute is already an array
-            # else convert it to an array
-            if isinstance(tmp_data[previous_attribute_name], list):
-                tmp_data[previous_attribute_name].append(attribute["value"])
-            else:
-                tmp_value = tmp_data[previous_attribute_name]
-                tmp_data[previous_attribute_name] = [tmp_value, attribute["value"]]
-
-        offset = new_offset
+            # if attribute has a name -> add it
+            # if attribute doesn't have a name -> it is part of an array
+            if attribute["name"]:
+                tmp_data[attribute["name"]] = attribute["value"]
+                previous_attribute_name = attribute["name"]
+            elif previous_attribute_name:
+                # check if attribute is already an array
+                # else convert it to an array
+                if isinstance(tmp_data[previous_attribute_name], list):
+                    tmp_data[previous_attribute_name].append(attribute["value"])
+                else:
+                    tmp_value = tmp_data[previous_attribute_name]
+                    tmp_data[previous_attribute_name] = [tmp_value, attribute["value"]]
+
+            offset = new_offset
 
     if isinstance(data[attribute_key], list):
         data[attribute_key].append(tmp_data)

tests/__snapshots__/test_parser.ambr

@@ -446,6 +446,31 @@
     ),
   })
 # ---
+# name: test_parse_empty_attribute_group
+  dict({
+    'data': b'',
+    'jobs': list([
+    ]),
+    'operation-attributes': dict({
+      'attributes-charset': 'utf-8',
+      'attributes-natural-language': 'en-US',
+      'printer-uri': 'ipp://printer.example.com:361/ipp/print',
+      'requesting-user-name': 'PythonIPP',
+    }),
+    'printers': list([
+    ]),
+    'request-id': 1,
+    'status-code': 11,
+    'unsupported-attributes': list([
+      dict({
+      }),
+    ]),
+    'version': tuple(
+      2,
+      0,
+    ),
+  })
+# ---
 # name: test_parse_epson_xp6000
   dict({
     'data': b'',

tests/fixtures/get-printer-attributes-empty-attribute-group.bin

@@ -163,3 +163,13 @@ def test_parse_kyocera_ecosys_m2540dn(snapshot: SnapshotAssertion) -> None:
 
     result = parser.parse(response)
     assert result == snapshot
+
+
+def test_parse_empty_attribute_group(snapshot: SnapshotAssertion) -> None:
+    """Test the parse method against a sample response with an empty attribute group."""
+    response = load_fixture_binary(
+        "get-printer-attributes-empty-attribute-group.bin",
+    )
+
+    result = parser.parse(response)
+    assert result == snapshot