Checks Options

• Type: object
• Default: See individual options below

Controls which warnings are emitted during the build process. Each option can be set to true (emit warning) or false (suppress warning).

circularDependency

• Type: boolean
• Default: false

Whether to emit warning when detecting circular dependency.

commonJsVariableInEsm

• Type: boolean
• Default: true

Whether to emit warning when detecting common js variable in esm.

configurationFieldConflict

• Type: boolean
• Default: true

Whether to emit warning when detecting configuration field conflict.

couldNotCleanDirectory

• Type: boolean
• Default: true

Whether to emit warning when detecting could not clean directory.

emptyImportMeta

• Type: boolean
• Default: true

Whether to emit warning when detecting empty import meta.

eval

• Type: boolean
• Default: true

Whether to emit warning when detecting eval.

filenameConflict

• Type: boolean
• Default: true

Whether to emit warning when detecting filename conflict.

importIsUndefined

• Type: boolean
• Default: true

Whether to emit warning when detecting import is undefined.

missingGlobalName

• Type: boolean
• Default: true

Whether to emit warning when detecting missing global name.

missingNameOptionForIifeExport

• Type: boolean
• Default: true

Whether to emit warning when detecting missing name option for iife export.

mixedExport

• Type: boolean
• Default: true

Whether to emit warning when detecting mixed export.

pluginTimings

• Type: boolean
• Default: true

Whether to emit warning when plugins significantly impact build performance.

When enabled, Rolldown measures time spent in each plugin hook. If plugins significantly impact build performance, a warning is emitted with a breakdown of plugin timings.

How it works:

1. Detection threshold: A warning is triggered when plugin time (total build time minus link stage time) exceeds 100x the link stage time. This threshold was determined by studying plugin impact on real-world projects.

2. Identifying plugins: When the threshold is exceeded, Rolldown reports up to 5 plugins that take longer than the average plugin time, sorted by duration. Each plugin shows its percentage of total plugin time.

WARNING

For hooks using ctx.resolve() or ctx.load(), the reported time includes waiting for other plugins, which may overestimate that plugin's actual cost.

Additionally, since plugin hooks execute concurrently, the statistics represent accumulated time rather than wall-clock time. The measured duration also includes Rust-side processing overhead, Tokio async scheduling overhead, NAPI data conversion overhead, and JavaScript event loop overhead.

preferBuiltinFeature

• Type: boolean
• Default: true

Whether to emit warning when detecting prefer builtin feature.

unresolvedEntry

• Type: boolean
• Default: true

Whether to emit warning when detecting unresolved entry.

unresolvedImport

• Type: boolean
• Default: true

Whether to emit warning when detecting unresolved import.

Example

import { defineConfig } from 'rolldown';

export default defineConfig({
  checks: {
    // Enable circular dependency warnings
    circularDependency: true,
    // Disable eval warnings
    eval: false,
    // Enable all other warnings (default)
  },
});