config

Configuration

Foundry's configuration system allows you to configure it's tools the way you want while also providing with a sensible set of defaults.

Profiles

Configurations can be arbitrarily namespaced by profiles. Foundry's default config is also named default, but can arbitrarily name and configure profiles as you like and set the FOUNDRY_PROFILE environment variable to the selected profile's name. This results in foundry's tools (forge) preferring the values in the profile with the named that's set in FOUNDRY_PROFILE.

foundry.toml

Foundry's tools search for a foundry.toml or the filename in a FOUNDRY_CONFIG environment variable starting at the current working directory. If it is not found, the parent directory, its parent directory, and so on are searched until the file is found or the root is reached. But the typical location for the global foundry.toml would be ~/.foundry/foundry.toml, which is also checked. If the path set in FOUNDRY_CONFIG is absolute, no such search takes place and the absolute path is used directly.

In foundry.toml you can define multiple profiles, therefore the file is assumed to be nested, so each top-level key declares a profile and its values configure the profile.

The following is an example of what such a file might look like. This can also be obtained with forge config

## defaults for _all_ profiles
[default]
src = "src"
out = "out"
libs = ["lib"]
solc = "0.8.10" # to use a specific local solc install set the path as `solc = "<path to solc>/solc"`
eth-rpc-url = "https://mainnet.infura.io"

## set only when the `hardhat` profile is selected
[hardhat]
src = "contracts"
out = "artifacts"
libs = ["node_modules"]

## set only when the `spells` profile is selected
[spells]
## --snip-- more settings

Default profile

When determining the profile to use, Config considers the following sources in ascending priority order to read from and merge, at the per-key level:

1. [Config::default()], which provides default values for all parameters.
2. foundry.toml or TOML file path in FOUNDRY_CONFIG environment variable.
3. FOUNDRY_ or DAPP_ prefixed environment variables.

The selected profile is the value of the FOUNDRY_PROFILE environment variable, or if it is not set, "default".

All Options

The following is a foundry.toml file with all configuration options set.

## defaults for _all_ profiles
[default]
src = 'src'
test = 'test'
out = 'out'
libs = ['lib']
remappings = []
# list of libraries to link in the form of `<path to lib>:<lib name>:<address>`: `"src/MyLib.sol:MyLib:0x8De6DDbCd5053d32292AAA0D2105A32d108484a6"`
# the <path to lib> supports remappings 
libraries = []
cache = true
cache_path = 'cache'
force = false
evm_version = 'london'
gas_reports = ['*']
## Sets the concrete solc version to use, this overrides the `auto_detect_solc` value
# solc_version = '0.8.10'
auto_detect_solc = true
offline = false
optimizer = true
optimizer_runs = 200
via_ir = false
verbosity = 0
ignored_error_codes = []
fuzz_runs = 256
ffi = false
sender = '0x00a329c0648769a73afac7f9381e08fb43dbea72'
tx_origin = '0x00a329c0648769a73afac7f9381e08fb43dbea72'
initial_balance = '0xffffffffffffffffffffffff'
block_number = 0
# NOTE due to a toml-rs limitation, this value needs to be a string if the desired gas limit exceeds `i64::MAX` (9223372036854775807)
gas_limit = 9223372036854775807
gas_price = 0
block_base_fee_per_gas = 0
block_coinbase = '0x0000000000000000000000000000000000000000'
block_timestamp = 0
block_difficulty = 0
# How to treat revert (and require) reason strings.
# Possible values are: "default", "strip", "debug" and "verboseDebug".
#  "default" does not inject compiler-generated revert strings and keeps user-supplied ones.
# "strip" removes all revert strings (if possible, i.e. if literals are used) keeping side-effects
# "debug" injects strings for compiler-generated internal reverts, implemented for ABI encoders V1 and V2 for now.
# "verboseDebug" even appends further information to user-supplied revert strings (not yet implemented)
revert_strings = "default"
# caches storage retrieved locally for certain chains and endpoints
# can also be restrictied to `chains = ["optimism", "mainnet"]`
# by default all endpoints will be cached, alternative options are "remote" for only caching non localhost endpoints and "<regex>"
# to disable storage caching entirely set `no_storage_caching = true`
rpc_storage_caching = { chains = "all", endpoints = "all" }
# this overrides `rpc_storage_caching` entirely
no_storage_caching = false
# use ipfs method to generate the metadata hash, solc's default.
# To not include the metadata hash, to allow for deterministic code: https://docs.soliditylang.org/en/latest/metadata.html, use "none"
bytecode_hash = "ipfs"
# If this option is enabled, Solc is instructed to generate output (bytecode) only for the required contracts
# this can reduce compile time for `forge test` a bit but is considered experimental at this point.
sparse_mode = false

Additional Optimizer settings

Optimizer components can be tweaked with the OptimizerDetails object:

See Compiler Input Description settings.optimizer.details

The optimizer_details (optimizerDetails also works) settings must be prefixed with the profile they correspond to: [default.optimizer_details] belongs to the [default] profile

[default.optimizer_details]
constantOptimizer = true
yul = true
# this sets the `yulDetails` of the `optimizer_details` for the `default` profile
[default.optimizer_details.yulDetails]
stackAllocation = true
optimizerSteps = 'dhfoDgvulfnTUtnIf'

Environment Variables

Foundry's tools read all environment variable names prefixed with FOUNDRY_ using the string after the _ as the name of a configuration value as the value of the parameter as the value itself. But the corresponding dapptools config vars are also supported, this means that FOUNDRY_SRC and DAPP_SRC are equivalent.

Environment variables take precedence over values in foundry.toml. Values are parsed as loose form of TOML syntax. Consider the following examples: