Joi: Joi.boolean() false positive to strings 'true' ans 'false'

[jrvldam]

Context

• node version: v8.15.0
• joi version: 14.3.1
• environment (node, browser): node
• used with (hapi, standalone, ...): express
• any other relevant information: no

What are you trying to achieve or the steps to reproduce ?

The validation for boolean type is returning a false positive when validating this strings: 'true' and 'false'.

const string = 'true'
const schema = Joi.boolean()

const validation = Joi.validate(string, schema)

Which result you had ?

validation.error === null

What did you expect ?

validation.error !== null

[WesTyler]

This is the expected behavior according to the API documentation-

If the validation convert option is on (enabled by default), a string (either "true" or "false") will be converted to a boolean if specified.

If you want "true" and "false" to error you can disable type conversion with .strict() or options:

Joi.boolean().strict().validate('true'); // ValidationError: "value" must be a boolean

Joi.boolean().validate('true', { convert: false }); // ValidationError: "value" must be a boolean

[jrvldam]

Thank you @WesTyler.
It's confusing to validate a string as a boolean when expecting a type validation by default, but it's true that this behavior is reported in the documentation.
Thank you for your time.

[Marsup]

Joi is originally made to be used on web scenarios, and query strings come as, well, strings... so it's the default behavior 🙂 It's no less surprising but at least now you know why 😉

[lock[bot]]

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