Package.json Validation

Packem validates your package.json to make sure the fields needed to publish a working package are configured correctly. This example shows the full validation.packageJson shape and what each toggle controls.

Overview

This example demonstrates:

• Enabling validation for individual package.json fields
• Allowing custom export conditions and extra export extensions
• Turning specific checks on or off

Configuration

// packem.config.ts
import { defineConfig } from '@visulima/packem/config'
import transformer from '@visulima/packem/transformer/esbuild'

export default defineConfig({
    transformer,
    validation: {
        packageJson: {
            // Validate individual fields
            name: true,
            main: true,
            module: true,
            types: true,
            typesVersions: true,
            exports: true,
            files: true,
            bin: true,
            dependencies: true,
            engines: true,
            sideEffects: true,

            // Allow custom export conditions without warnings
            extraConditions: ["custom-bundler", "my-framework"],

            // Allow extra file extensions in the exports field
            allowedExportExtensions: [".css", ".wasm"],
        },
    },
})

Available checks

Every field below is an individual boolean toggle under validation.packageJson:

What this does

• Packem checks that the enabled fields exist and point at files the build actually produces.
• exports validation flags unknown export conditions. Add custom ones to extraConditions so they don't warn (see the Extra Conditions example).
• allowedExportExtensions lets non-JS outputs (such as .css or .wasm) appear in exports without triggering an "unexpected extension" warning.

Disabling a specific check

Set any field toggle to false to skip just that check while keeping the rest:

validation: {
    packageJson: {
        // Validate everything except the engines field
        name: true,
        main: true,
        types: true,
        exports: true,
        engines: false,
    },
}

Disabling all validation

To turn off every validator (package.json, bundle size, and dependencies) set validation to false:

export default defineConfig({
    transformer,
    validation: false,
})

You can also pass --no-validation on the CLI:

packem build --no-validation

Related Examples

• Extra Conditions - Configure custom export conditions
• Dependency Validation - Validate dependencies and detect issues
• Bundle Size Limits - Set up bundle size validation and limits