Naming Rules

Overview

In Clean Architecture, domain and usecase layers should not contain technology-specific implementation names. For example, symbols like AwsClient or RedisQueue inside a usecase violate layer responsibilities.

mille’s naming convention check lets you define forbidden keywords per layer, scanning file names, symbol names, variable names, comments, and string literals.

[[layers]] Naming Options

Key	Default	Description
name_deny	[]	Forbidden keywords (case-insensitive, partial match)
name_allow	[]	Substrings stripped before name_deny check (suppresses false positives)
name_targets	["file", "symbol", "variable", "comment", "string_literal"]	Which targets to check. Defaults to all
name_deny_ignore	[]	Glob patterns for files excluded from naming checks

Basic Example

[[layers]]
name            = "domain"
paths           = ["src/domain/**"]
dependency_mode = "opt-in"
allow           = []
external_mode   = "opt-in"
external_allow  = ["serde"]

# Flag infrastructure-specific technology names in the domain layer
name_deny = ["aws", "gcp", "azure", "redis", "kafka", "mysql", "postgres"]

Matching Rules

• Case-insensitive: AWS = aws = Aws
• Partial match: ManageGcpResource matches gcp
• First match only: one violation reported per name per layer

name_allow — Suppressing False Positives

Partial matching can cause unintended matches:

"ImportCategory" → matches "go" (because "cate_go_ry" contains "go")

Register substrings in name_allow to strip them before checking:

name_deny  = ["go", "aws"]
name_allow = ["category", "algorithm", "cargo"]

When checking ImportCategory, "category" is stripped first → "import" remains → no match for "go".

Caution

name_allow still reports a violation if a keyword remains after stripping. For example, GoCategory → strip "category" → "go" remains → violation.

name_targets — Narrowing Check Scope

By default, all 5 target types are checked. You can narrow the scope:

# Only check symbol and file names (allow comments and variables)
name_targets = ["file", "symbol"]

Target	What is checked
file	File basename (without extension)
symbol	Function, class, struct, enum, trait, interface, type alias names
variable	Variable, const, let, static declaration names
comment	Inline comment content
string_literal	String literal content

name_deny_ignore — Excluding Specific Files

Exclude files from naming checks using glob patterns (e.g., test files):

name_deny        = ["aws", "gcp"]
name_deny_ignore = ["**/test_*.rs", "tests/**", "**/*_test.go"]

Severity

The default severity for naming violations is "error". For gradual adoption, set it to "warning":

[severity]
naming_violation = "warning"

See Severity for details.

Supported Languages

All 8 languages (Rust, TypeScript/JavaScript, Python, Go, Java, Kotlin, PHP, C) support all targets: symbols, variables, comments, string literals, and file names.

How to Fix Violations

When a naming violation is detected, the recommended fix is architectural — not just renaming:

1. Abstraction: Define a MessageQueue trait in domain, implement RedisQueue in infrastructure
2. Dependency Injection: Wire concrete implementations in the main layer
3. Move to infrastructure: Relocate technology-specific logic to the infrastructure layer

// ❌ Technology name leaks into domain
struct RedisUserRepository { ... }

// ✅ Domain only defines abstract interfaces
trait UserRepository { ... }
// Infrastructure provides the implementation
struct RedisUserRepository { ... }