Configuration

Cargo Bylaw discovers bylaw.toml from the current directory upward, or accepts --config. Unknown fields and unsupported configuration versions are errors.

Analysis

version = 1

[analysis]
manifest_path = "Cargo.toml"
packages = ["shop-api"]
features = ["postgres"]
target_kinds = ["library", "binary"]
incomplete = "deny"
proc_macros = true
build_scripts = true

[output]
format = "human"

Library and binary targets are analyzed by default. Tests, examples, benches, build scripts, and proc-macro targets must be selected explicitly. incomplete = "deny" is the default; cargo bylaw check --allow-incomplete changes incompleteness to warnings for that invocation.

Output is human by default and can be set to json; --format overrides the configuration for one invocation. JSON output uses a top-level version field and either a structured report or error object.

cargo bylaw check exits with 0 for a successful check, 1 for architecture violations, 2 for configuration errors, and 3 for analyzer failures.

Selectors

[selectors.domain]
packages = ["shop-domain"]

[selectors.domain-modules]
crates = ["shop"]
modules = ["shop::domain::**"]

[selectors.serialization]
external_crates = ["serde", "serde_json"]

Values within a field are alternatives. Different fields are combined, so the domain-modules selector means modules matching the path in the shop crate. Rust path patterns use * for one :: segment and ** for zero or more.

Dependency rules

[[rule]]
id = "domain-is-internal"
kind = "forbid-dependencies"
from = "domain"
to = ["persistence", "api"]
scope = "both"
because = "domain policy must not depend on adapters"

[[rule]]
id = "domain-allowlist"
kind = "only-dependencies"
from = "domain"
allowed = ["domain", "serialization"]
scope = "actual"
allow_toolchain = true
allow_self = true

scope is actual, declared, or both.

Layers

[[rule]]
id = "application-layers"
kind = "layers"
scope = "both"

[[rule.layers]]
name = "domain"
selector = "domain"

[[rule.layers]]
name = "persistence"
selector = "persistence"

[[rule.dependencies]]
from = "persistence"
may_depend_on = ["domain"]

Omitting a layer from may_depend_on forbids that direction. Dependencies within the same layer are allowed.

Cycles

[[rule]]
id = "model-crates-are-acyclic"
kind = "no-cycles"
within = ["domain", "persistence", "api"]
grouping = "crates"
scope = "actual"

Grouping can be components, modules, crates, or named slices.