duplicatePackage

Warns when multiple versions of an Effect-related package are detected in the program

Property	Value
Category	Correctness
Default severity	warning
Fixable	No
Effect versions	v3, v4
Diagnostic codes	TS377051
Language Service name	duplicatePackage
Oxlint name	effecttsgo/duplicate-package

Preview

import * as Effect from "effect/Effect"

// This preview only reports when the workspace resolves duplicated
// Effect package versions.
export const preview = Effect.succeed(true)

This rule depends on project context and does not emit a diagnostic in the standalone preview.

Language Service Configuration

See the Language Service setup guide for installation instructions.

{
  "$schema": "./node_modules/@effect/tsgo/schema.json",
  "compilerOptions": {
    "plugins": [
      {
        "name": "@effect/language-service",
        "diagnosticSeverity": {
          "duplicatePackage": "warning"
        }
      }
    ]
  }
}

Oxlint Configuration

See the Oxlint setup guide for installation and patching instructions.

{
  "$schema": "./node_modules/@effect/tsgo/oxlint-schema.json",
  "options": {
    "typeAware": true
  },
  "plugins": ["effecttsgo"],
  "rules": {
    "effecttsgo/duplicate-package": "warn"
  }
}