fix Bottle issue with umlauts and special characters

brother_ql_web/web.py

@@ -53,7 +53,18 @@ def labeldesigner() -> dict[str, Any]:
 
 
 def get_label_parameters(request: bottle.BaseRequest) -> LabelParameters:
-    d = request.params.decode()  # UTF-8 decoded form data
+    # As we have strings, *bottle* would try to generate Latin-1 bytes from it
+    # before decoding it back to UTF-8. This seems to break some umlauts, thus
+    # resulting in UnicodeEncodeErrors being raised when going back to UTF-8.
+    # For now, we just state that we always receive clean UTF-8 data and thus
+    # the recode operations just can be omitted. All external API users are
+    # responsible for passing clean data.
+    # References:
+    #   * https://github.com/bottlepy/bottle/blob/99341ff3791b2e7e705d7373e71937e9018eb081/bottle.py#L2197-L2203  # noqa: E501
+    #   * https://github.com/FriedrichFroebel/brother_ql_web/issues/9
+    parameters = request.params
+    parameters.recode_unicode = False
+    d = parameters.decode()  # UTF-8 decoded form data
 
     font_family = d.get("font_family").rpartition("(")[0].strip()
     font_style = d.get("font_family").rpartition("(")[2].rstrip(")")

tests/test_web.py

@@ -203,6 +203,35 @@ def test_plain_bytes(self) -> None:
         with as_file(reference) as path:
             self.assertEqual(path.read_bytes(), response.content)
 
+    def test_special_characters(self) -> None:
+        self.run_server()
+        # Minimal copy from the Firefox developer tools.
+        headers = {
+            "Content-Type": "multipart/form-data; boundary=---------------------------381934621323024354152349680295"  # noqa: E501
+        }
+        body = """
+-----------------------------381934621323024354152349680295
+Content-Disposition: form-data; name="text"
+
+abcdefgö+ëŠ
+-----------------------------381934621323024354152349680295
+Content-Disposition: form-data; name="font_family"
+
+Roboto (Medium)
+-----------------------------381934621323024354152349680295
+Content-Disposition: form-data; name="label_size"
+
+62
+-----------------------------381934621323024354152349680295--
+""".encode()
+        response = requests.post(
+            "http://localhost:8013/api/preview/text?return_format=png",
+            data=body,
+            headers=headers,
+        )
+        self.assertEqual(200, response.status_code)
+        self.assertLessEqual(14000, len(response.content))  # 14061 bytes
+
 
 class PrintTextTestCase(TestCase):
     def test_error(self) -> None: