Fix shared-state/thread-safety bug in Payment.capture() (mutable default argument)#331
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capture() used a mutable default argument (data={}) and mutated it
(data['amount'] = amount). The default dict is created once and shared
across every call, every Client instance and every thread, so:
* state leaks between calls: after capture(id, 4242) with no data, the
function's default is permanently {'amount': 4242}; and
* on a Client shared across threads (the documented usage) concurrent
capture() calls race on the shared dict and can post one payment's
amount for another payment.
Fixed by using data=None and building a fresh dict per call (also avoids
mutating a caller-supplied dict). Removes the # nosemgrep suppression
that was hiding the mutable-default warning.
Refs razorpay#134.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Summary
Payment.capture()uses a mutable default argument (data={}) and mutates it (data['amount'] = amount). Because the default{}is created once and shared across every call, everyClientinstance, and every thread, captured state leaks between calls and — on aClientshared across threads (the documented usage) — concurrent captures race on the shared dict.This was previously flagged in #134 and silenced with a
# nosemgrepsuppression rather than fixed.Impact
client.payment.capture(id, 4242)with nodata, the function's default is permanently{'amount': 4242}.capture()concurrently can post one payment's amount for a different payment. In a minimal 2-thread reproduction (25 captures each, amounts 100 vs 999), 47 of 50 calls posted the wrong amount. After the fix: 0 of 50.Fix
Use
data=Noneand build a fresh dict per call (this also avoids mutating a caller-supplied dict). The now-unnecessary# nosemgrepsuppression is removed.Tests
Added two regression tests to
tests/test_client_payment.py:test_payment_capture_does_not_leak_state_into_defaulttest_payment_capture_does_not_mutate_caller_dictFull suite:
159 passed, 1 skipped.Refs #134.