`json.loads` ignores `sys.int_max_str_digits` (decodes an over-long int instead of raising `ValueError`)

myers

Feature

json.loads should honor the interpreter's integer string-conversion limit (sys.set_int_max_str_digits, PEP 651). RustPython's native _json scanner (the Rust-implemented accelerated module, RustPython's analog of CPython's C _json) decodes an over-long integer literal instead of raising ValueError. The pure-Python decoder already honors the limit (its int conversion goes through int(str)); only the native _json scanner diverges.

Surfaced by running CPython's own stdlib test suite under RustPython — test_json.test_decode::TestCDecode.test_limit_int fails. The minimal standalone reproduction:

Reproduction

import sys, json
sys.set_int_max_str_digits(5000)
json.loads('1' * 5001)

CPython 3.14:

ValueError: Exceeds the limit (5000 digits) for integer string conversion: value has 5001 digits

RustPython:

(returns the 5001-digit integer — no error)

Python Documentation or reference to CPython source code

Limit / API: sys.set_int_max_str_digits (PEP 651).
CPython enforces it in _match_number_unicode, which builds the int via PyLong_FromString (limit-aware).
RustPython diverges in JsonScanner::parse_number, which builds the integer with BigInt::from_str(buf) and never consults sys.int_max_str_digits.

Suggested fix

Route the integer construction through rustpython_common::int::bytes_to_int with the live vm.state.int_max_str_digits (the same path the int() builtin uses), so the limit is read per-call and sys.set_int_max_str_digits / adjust_int_max_str_digits take effect. Float parsing is unaffected. This also unblocks test_json.test_decode::TestCDecode.test_limit_int.

Investigated and drafted with AI assistance (Claude Code), reviewed by a human before filing, per RustPython's AI policy.