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The Boolean Validator plugin for Flatfile provides comprehensive boolean validation for specified fields. It is designed to handle various representations of boolean values, not just true and false. Key features include two main validation modes: ‘strict’ (only accepts true/false boolean types) and ‘truthy’ (accepts values like ‘yes’, ‘no’, ‘y’, ‘n’, etc.). The plugin offers multi-language support for these truthy values (English, Spanish, French, German) and allows for custom mappings. It is highly configurable, with options to control case sensitivity, how null/undefined values are handled, and whether to automatically convert non-boolean values.

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Installation

Install the plugin using npm: 
npm install @flatfile/plugin-validate-boolean

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Configuration & Parameters

The plugin is configured with a single object, BooleanValidatorConfig, containing the following options:

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Required Parameters

fields string[]
  • An array of field keys (column names) to which the boolean validation should be applied.
validationType 'strict' | 'truthy'
  • The type of validation to perform:
    • 'strict': Only allows true and false boolean values
    • 'truthy': Allows string representations like ‘yes’, ‘no’, etc.

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Optional Parameters

sheetSlug string
  • The slug of a specific sheet to apply the validation to
  • Default: '**' (all sheets)
language 'en' | 'es' | 'fr' | 'de'
  • Specifies the language for predefined ‘truthy’ mappings
  • Default: 'en'
customMapping Record<string, boolean>
  • Custom string-to-boolean mappings that override language-specific mappings
  • Example: { 'ja': true, 'nein': false }
caseSensitive boolean
  • Controls case sensitivity for string comparisons during ‘truthy’ validation
  • Default: false
handleNull 'error' | 'false' | 'true' | 'skip'
  • Defines how to handle null or undefined values:
    • 'error': Adds an error to the record
    • 'false': Converts the value to false
    • 'true': Converts the value to true
    • 'skip': Ignores the value without adding an error
  • Default: 'skip'
convertNonBoolean boolean
  • Attempts to convert non-boolean values using JavaScript’s Boolean() casting
  • Default: false
defaultValue boolean | 'skip'
  • Default value for invalid inputs instead of adding an error
  • Default: undefined (raises an error)
customErrorMessages object
  • Custom error messages for validation failures
  • Properties: invalidBoolean, invalidTruthy, nullValue

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Usage Examples

import { FlatfileListener } from '@flatfile/listener';
import { validateBoolean } from '@flatfile/plugin-validate-boolean';

export default function(listener) {
  // Basic strict validation
  listener.use(
    validateBoolean({
      fields: ['isActive'],
      validationType: 'strict',
    })
  );
}

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Advanced Configuration

import { FlatfileListener } from '@flatfile/listener';
import { validateBoolean } from '@flatfile/plugin-validate-boolean';

export default function(listener) {
  listener.use(
    validateBoolean({
      sheetSlug: 'contacts',
      fields: ['hasSubscription', 'isPremium'],
      validationType: 'truthy',
      language: 'es', // Use Spanish mappings: 'sí', 'no'
      handleNull: 'false', // Treat null/undefined as false
      defaultValue: false, // Set invalid values to false instead of erroring
      customErrorMessages: {
        nullValue: 'El campo no puede estar vacío.',
      },
    })
  );
}

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Using Helper Functions

import { validateBooleanField } from '@flatfile/plugin-validate-boolean';

const myValue = 'Y';
const result = validateBooleanField(myValue, {
  fields: ['customField'],
  validationType: 'truthy',
  language: 'en', // 'y' is a valid mapping in English
});

if (result.error) {
  console.error(`Validation failed: ${result.error}`);
} else {
  console.log(`Validated value: ${result.value}`); // Outputs: Validated value: true
}

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API Reference

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validateBoolean

The main entry point for the plugin that configures and returns a Flatfile listener. Signature: 
validateBoolean(config: BooleanValidatorConfig): (listener: FlatfileListener) => void
Parameters:
  • config - Configuration object for the validator
Returns: A function that can be passed to listener.use() to register the plugin.

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validateBooleanField

A utility function that runs the complete validation logic for a single value. Signature: 
validateBooleanField(value: any, config: BooleanValidatorConfig): { value: boolean | null; error: string | null }
Parameters:
  • value - The value to validate
  • config - The configuration object
Returns: Object with value (validated boolean or null) and error (error message or null)

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validateStrictBoolean

Validates that a value is strictly a boolean true or false. Signature: 
validateStrictBoolean(value: any, config: BooleanValidatorConfig): { value: boolean | null; error: string | null }

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validateTruthyBoolean

Validates that a value corresponds to a “truthy” or “falsy” representation. Signature: 
validateTruthyBoolean(value: any, config: BooleanValidatorConfig): { value: boolean | null; error: string | null }

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handleNullValue

Processes a null or undefined value according to the handleNull configuration. Signature: 
handleNullValue(value: any, config: BooleanValidatorConfig): { value: boolean | null; error: string | null }

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handleInvalidValue

Processes a value that has been identified as invalid. Signature: 
handleInvalidValue(value: any, config: BooleanValidatorConfig): { value: boolean | null; error: string | null }

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Troubleshooting

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Validation Not Applied

  • Ensure the fields array contains the correct field keys
  • Verify the sheetSlug (if used) matches the target sheet

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Case Sensitivity Issues

For ‘truthy’ validation, if values like ‘YES’ aren’t being validated correctly, check the caseSensitive option. It defaults to false, but if set to true, the case must match exactly.

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Unexpected Results

Remember the order of operations:
  1. Null handling is checked first
  2. Specific validation type (‘strict’ or ‘truthy’) is applied
  3. defaultValue is used as a final fallback for invalid values

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Notes

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Default Behavior

If only the required fields and validationType options are provided, the plugin will apply validation to the specified fields on all sheets. For ‘truthy’ validation, it uses case-insensitive English mappings (‘yes’/‘no’). Null or undefined values are skipped by default.

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Special Considerations

  • The plugin supports built-in truthy/falsy mappings for English (‘en’), Spanish (‘es’), French (‘fr’), and German (‘de’)
  • Custom mappings (customMapping) take precedence over language-based default mappings
  • The sheetSlug option allows applying different validation rules to different sheets within the same workbook

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Error Handling Patterns

  • The main plugin does not throw exceptions; it adds errors directly to Flatfile records
  • When a defaultValue is provided, the plugin corrects invalid values and adds an informational message for auditing
  • Helper functions return a consistent { value, error } object pattern for easy error checking