@studnicky/domain-purity

Forbids configurably-listed impure imports and non-deterministic calls inside files resolved to the domain layer of a hexagonal architecture. The domain layer is meant to hold pure business logic: no I/O, no wall-clock or random-number dependence, nothing that would make the same inputs produce different outputs across runs. The rule resolves each file's layer the same way layer-import-boundary does (via layers/sourceRoot/aliasPrefixes), then — for files in the domain layer (configurable via domainLayerName, default "domain") — reports any import whose specifier matches (or is a submodule of) an entry in forbiddenImports, and any dotted call expression (Identifier or Identifier.Identifier form) matching an entry in forbiddenCalls. Files outside the domain layer are never checked. This rule is typically wired together with layer-import-boundary, adapter-only-import, and known-types-outside-adapters via the HexagonalSuite.create({...}) factory export, since all four share the same layers/sourceRoot configuration — but it is fully usable and configurable on its own.

Fixable: No · Options: Yes · Suggested severity: error

Options

Name	Type	Default	Description
layers	string[]	(required)	Ordered list of enforced layer names, e.g. ["domain", "ports", "application", "adapters", "infrastructure"].
sourceRoot	string	(required)	Path segment(s) after which the layer name appears, e.g. "src".
aliasPrefixes	object	undefined	Map of path-alias prefixes (e.g. "@domain/") to their layer name.
allowedImports	object	undefined	Override of the default allow-matrix: source layer name → list of layers it may import from.
domainLayerName	string	"domain"	Name of the layer treated as the pure-data domain layer, e.g. "domain" or "entities".
forbiddenImports	string[]	undefined	Bare import specifiers or roots forbidden in domain-layer files, e.g. ["fs", "axios", "node:fs"].
forbiddenCalls	string[]	undefined	Dotted call expressions forbidden in domain-layer files, e.g. ["Date.now", "Math.random"].

✗ Incorrect

// domain-layer file (/repo/src/domain/user/User.ts) importing a forbidden import — flagged
import axios from 'axios';

// domain-layer file calling a forbidden non-deterministic call — flagged
const timestamp = Date.now();

// domain-layer file importing a submodule of a forbidden root — flagged via prefix match
import promises from 'node:fs/promises';

✓ Correct

// domain-layer file importing something not in forbiddenImports — not flagged
import { User } from './User.js';

// non-domain-layer file (/repo/src/application/UserService.ts) importing a
// forbidden import — not flagged, the rule only applies inside the domain layer
import axios from 'axios';

// domain-layer file calling something not in forbiddenCalls — not flagged
const id = crypto.randomUUID();