feat: improve forge test configuration for checking gas section snapshots

[turbocrime]

Component

Forge

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

• Foundry
• Foundryup

What version of Foundry are you on?

forge Version: 0.3.1-nightly Commit SHA: fea3885 Build Timestamp: 2025-01-21T16:53:17.552998000Z (1737478397) Build Profile: release

What version of Foundryup are you on?

No response

What command(s) is the bug in?

forge

Operating System

macOS (Apple Silicon)

Describe the bug

the env var FORGE_SNAPSHOT_CHECK is available to enable checking section snapshots (those snapshots defined with vm.startSnapshotGas). but its use is not consistent with other configuration.

foundry/crates/forge/bin/cmd/test/mod.rs

Lines 665 to 667 in 5993795

	// Check for differences in gas snapshots if `FORGE_SNAPSHOT_CHECK` is set.
	// Exiting early with code 1 if differences are found.
	if std::env::var("FORGE_SNAPSHOT_CHECK").is_ok() {

problems

• there is no equivalent command-line flag
• configuration is not located with other env var access. a call to std::env::var appears directly in the conditional
• the value of the env var is not parsed (so FORGE_SNAPSHOT_CHECK="false" or even FORGE_SNAPSHOT_CHECK="" creates the same behavior as FORGE_SNAPSHOT_CHECK="true")

consistency

it seems like figment is intended to provide access to configuration, but it is inconsistently used across the project. there are other examples of configuration that does not arrive via figment.

in this case, the forge test command uses clap arg macros for command-line arguments, and some of the arg identify env variables as sources of argument values. the defined clap args are then merged into figment with merge_impl_figment_convert

however, FORGE_SNAPSHOT_CHECK has no associated arg, because it is accessed directly, and is not merged.

suggestions

• access to env should be collected in one location
• a command-line option should be available to override any env configuration
• env booleans should be parsed for value instead of a simple presence condition

defining clap args for snapshot check could achieve the suggestions.

[zerosnacks]

Agreed, in favor of the proposed change to add a bool entry snapshot_check in config w/ FORGE_SNAPSHOT_CHECK

We can then update this check to use the parsed value whilst maintaining backwards compatibility

The Foundry book would need to have a minor update: https://book.getfoundry.sh/forge/gas-section-snapshots