Fix mutable default argument anti-pattern for Random objects #4433
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Looks like there were some tests which dependended on the buggy logic. We want the parent block from prepare_random_pow_block to be different.
leolara
previously approved these changes
Jul 8, 2025
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For the previous release (commit), I noticed that many of the test files were different. I found that we were using
rng=Random(...)in function declarations which will not work like we want. The core issue is that default arguments are evaluated once when the function is defined, not each time it's called. So when we userng=Random(...)in a function declaration, that sameRandomobject instance gets shared across all function calls, accumulating state changes. For reference, see Mutable Default Arguments.I tested this by running the following multiple times, confirming that the hash was the same each time:
rm -rf ../consensus-spec-tests make reftests preset=minimal find ../consensus-spec-tests -type f -exec sha256sum {} + | sort | sha256sumTo be clear, the next release's diff will be large, but the next next release's diff will be small 😄