onwarn()

• Type: optional onwarn: (warning, defaultHandler) => void

Defined in: options/input-options.ts:427

A function that will intercept warning messages.

If the default handler is invoked, the log will be handled as a warning. If both an onLog and onwarn handler are provided, the onwarn handler will only be invoked if onLog calls its default handler with a level of "warn".

Parameters

warning

RollupLog

defaultHandler

(warning) => void

Returns

void

Deprecated

This is a legacy API. Consider using onLog instead for better control over all log types.

To migrate from onwarn to onLog, check the level parameter to filter for warnings:

// Before: Using `onwarn`
export default {
  onwarn(warning, defaultHandler) {
    // Suppress certain warnings
    if (warning.code === 'CIRCULAR_DEPENDENCY') return;
    // Handle other warnings with default behavior
    defaultHandler(warning);
  },
};

// After: Using `onLog`
export default {
  onLog(level, log, defaultHandler) {
    // Handle only warnings (same behavior as `onwarn`)
    if (level === 'warn') {
      // Suppress certain warnings
      if (log.code === 'CIRCULAR_DEPENDENCY') return;
      // Handle other warnings with default behavior
      defaultHandler(level, log);
    } else {
      // Let other log levels pass through
      defaultHandler(level, log);
    }
  },
};