fix(server): correct poor rate limit responses detection (jxmorris12#211)

Author: mdevolde

CHANGELOG.md

@@ -33,6 +33,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/2.0.0/),
 ### Fixed
 - Corrected a bug in `language_tool_python.config_file.LanguageToolConfig` where directory paths were incorrectly rejected by the path validator.
 - Fixed a bug in `LanguageTool._start_server_on_free_port` where `_url` was not updated when retrying on a different port, causing all subsequent server requests to target the wrong (original) port.
+- Fixed a bug in `LanguageTool._query_server` where `RateLimitError` was only raised when the rate-limit response body was invalid JSON, a valid JSON body with status 426 was silently returned as data instead (for now, the body from LanguageTool for rate-limiting responses is "Upgrade Required", which is not valid JSON, but this may change in the future).
 
 ### Removed
 - **Breaking:** Removed all functions and classes previously deprecated in v3.3.0:

src/language_tool_python/server.py

@@ -1054,6 +1054,12 @@ def _query_server(
                         timeout=self._TIMEOUT,
                     )
                 with response_context as response:
+                    if response.status_code == _HTTP_STATUS_RATE_LIMIT:
+                        err = (
+                            "You have exceeded the rate limit for the free "
+                            "LanguageTool API. Please try again later."
+                        )
+                        raise RateLimitError(err)
                     try:
                         data: object = response.json()
                     except json.decoder.JSONDecodeError as e:
@@ -1063,12 +1069,6 @@ def _query_server(
                             e,
                         )
                         logger.debug("Status code: %s", response.status_code)
-                        if response.status_code == _HTTP_STATUS_RATE_LIMIT:
-                            err = (
-                                "You have exceeded the rate limit for the free "
-                                "LanguageTool API. Please try again later."
-                            )
-                            raise RateLimitError(err) from e
                         raise LanguageToolError(
                             _decode_response_content(response),
                         ) from e