Use generic error handling for 4XX empty responses #3602
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When XML parsing fails due to empty or malformed responses, users now receive the actual HTTP error response from the service alongside the parsing error, providing useful information about what actually happened. Before: ResponseParserError: Unable to parse response (no element found: line 1, column 0), invalid XML received. Further retries may succeed: b'' After: ResponseParserError: Unable to parse response (no element found: line 1, column 0), invalid XML received. Further retries may succeed: b'' HTTP 413: Content Too Large This exposes the real service error (HTTP 413: Content Too Large) that was previously hidden behind cryptic XML parsing failures, giving users actionable information about why their request failed.
adev-code
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adev-code
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## develop #3602 +/- ##
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- Coverage 93.17% 92.67% -0.50%
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Files 68 68
Lines 15411 15573 +162
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+ Hits 14359 14433 +74
- Misses 1052 1140 +88 ☔ View full report in Codecov by Sentry. 🚀 New features to boost your workflow:
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The HTTP 413 status message differs between Python versions:
- Python 3.13: "Content Too Large"
- Python 3.11: "Request Entity Too Large"
Updated test assertions to use assertIn("HTTP 413:") instead of exact
string matching to ensure tests pass across supported Python versions
while still verifying that HTTP status context is properly added to
XML parsing errors.
Add hasattr(e, 'add_note') checks before calling add_note() to ensure compatibility with Python 3.9 and 3.10 where PEP 678 exception notes are not available. The enhanced HTTP status context will only be added in Python 3.11+ while maintaining backward compatibility.
nateprewitt
reviewed
Nov 25, 2025
botocore/parsers.py
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| response['status_code'], '' | ||
| ) | ||
| if status_message: | ||
| if status_message and hasattr(e, 'add_note'): |
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I think this requires Python 3.11+ so this is probably not the approach we want to take to make sure this works everywhere.
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Thanks Nate, yes I only found out from the CI tests and trying options. Will check for other ways.
Enhanced ResponseParserError messages to include HTTP status codes and messages when XML parsing fails, providing better debugging context for users while maintaining full backward compatibility. Changes: - Modified QueryParser._do_error_parse() to append HTTP status context - Modified RestXMLParser._parse_error_from_body() to append HTTP status context - Enhanced error messages format: "original error (HTTP 413: Content Too Large)" - Preserves original ResponseParserError exception type for compatibility - Added comprehensive tests for both parser classes - Tests handle Python version differences in HTTP status messages
- Improve code readability while maintaining identical functionality
Extend generic error response detection from 5XX to 4XX status codes to prevent XML parsing failures when services return empty bodies. Fixes parsing crashes for cases like AWS Services returning HTTP 413 with empty body, now shows "Content Too Large" instead of "Unable to parse response (no element found: line 1, column 0)".
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Problem
When AWS services return 4XX errors with empty bodies, users receive XML parsing errors instead of meaningful HTTP status messages. For example, service returns HTTP 413 with an empty body when request size limits are exceeded, but users see:
Solution
This PR extends generic error handling from 5XX to 4XX status codes, preventing parsing failures and surfacing the actual HTTP error, for example:
Backwards Compatibility