Fuzz Seed is not read from foundry.toml on forge snapshot

[marktoda]

Component

Forge

Have you ensured that all of these are up to date?

• Foundry
• Foundryup

What version of Foundry are you on?

forge 0.2.0 (94ae897 2023-10-31T00:16:51.730405056Z)

What command(s) is the bug in?

forge snapshot

Operating System

Linux

Describe the bug

When running forge snapshot, fuzz seed as defined in foundry.toml is not honored. When passing it in as an env variable via FOUNDRY_FUZZ_SEED, it works fine.

behavior:
in foundry.toml, I've set

[fuzz]
runs = 100
seed = 0x4444

When running forge snapshot, it works fine and uses 100 runs. Then I set the seed in the environment with

FOUNDRY_FUZZ_SEED=0x4444 forge snapshot and it results in a different snapshot file. I would expect this to be the same seed as set in foundry.toml.

This causes a problem in CI where locally run snapshots do not match CI-run snapshots unless environment variable seed is set.

Reference PR from uniswap/v4-core where we had to set fuzz seed in env Uniswap/v4-core#331

[marktoda]

ref think this would solve #5689

[marktoda]

I see now that this is likely because we use STATIC_FUZZ_SEED for snapshot https://github.com/foundry-rs/foundry/blob/30ae702a31e175ca9c2c23bba71ee9d8520c8e45/crates/forge/bin/cmd/snapshot.rs#L101C56-L101C72 which overrides the foundry.toml version

but then why does the env variable affect it? and why does the STATIC_FUZZ_SEED result in differing outputs run by run?

[marktoda]

nvm after more research seems the static seed works fine, i think the issue is diff rng between mac vs linux? i.e. when running on local linux machine vs linux CI it works but mac local vs linux CI fails