build(flake8): Add S019 rule banning reserved LogRecord keys in logging extra=#117562
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Passing a reserved LogRecord attribute (name, message, args, module, etc.) as a key in a logging extra= dict raises KeyError: "Attempt to overwrite 'X' in LogRecord" at runtime. Nothing static caught this, and it recently caused a silent production incident. Add a custom S019 flake8 rule that flags literal extra= dict keys colliding with reserved LogRecord attributes on logging calls. Only literal dicts with constant string keys are checked; dynamic dicts cannot be detected statically.
Two existing logging calls passed reserved LogRecord keys in extra=, which raise KeyError when the log line fires: - apigateway/proxy.py: "message" -> "error" (breaker-config warning) - preprod/snapshots/tasks.py: "name" -> "image_name" (also fixed in #117550) These are the only repo-wide violations the new S019 rule surfaces.
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Scope: Backend
joshuarli
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Jun 12, 2026
markstory
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Jun 12, 2026
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Summary
Passing a reserved
LogRecordattribute (name,message,args,module, …) as a key in a loggingextra=dict raisesKeyError: "Attempt to overwrite 'X' in LogRecord"at runtime, when the log line actually fires. Nothing static catches it — it passes ruff, mypy, and a human skim — and it recently caused a silent production incident in preprod snapshots (the log call meant to aid debugging was the thing that crashed; see #117550).This adds a custom S019 flake8 rule (Sentry's
S###family intools/flake8_plugin.py) that flags this class before runtime, and fixes the only two existing violations it surfaces repo-wide.This follows up a review question on #117550 ("can this class of problem be prevented before runtime?").
Changes
tools/flake8_plugin.py): flagslogger.<level>(..., extra={...})calls whoseextradict has a literal string key colliding with a reservedLogRecordattribute. Auto-registered via the existingS=prefix plugin (no config change).test_S019(tests/tools/test_flake8_plugin.py): coversname/messagehits, a non-reserved key (ok), and a dynamicextra=var(not flagged).hybridcloud/apigateway/proxy.py:"message"→"error"in a breaker-config warning (would have crashed when invalid config was hit).preprod/snapshots/tasks.py:"name"→"image_name"(same fix as fix(preprod): Stop chunk crash from reserved LogRecord key #117550; identical change, no conflict whichever merges first).Known limitation
Only literal
extra={...}dicts with constant string keys are checked. Dynamic dicts (extra=some_var,extra={**spread}, computed keys) can't be detected statically — but the literal case is the one that actually bites.Test Plan
test_S019passes; fulltests/tools/test_flake8_plugin.pysuite green (18 tests)flake8 --select=S019 src tests toolsreports clean after the two fixes (was 2 hits before)