Yup: Deep Validation in Array of Objects

I solved it using compact() (filtering out falsely values) together with setTimeout after the FieldArray modifier function:

const validationSchema = Yup.object().shape({
  subject: Yup.string().required(i18n.t('required-field')),
  description: Yup.string(),
  daysOfWeek: Yup.array()
    .of(
      Yup.object().shape({
        dayOfWeek: Yup.string(),
        checked: Yup.boolean(),
      })
    )
    .compact((v) => !v.checked)
    .required(i18n.t('required-field')),
  taskSchedules: Yup.array(),
});

And in form:

<Checkbox
  value={day.dayOfWeek}
  checked={day.checked}
  onChange={(e) => {
    replace(idx, { ...day, checked: !day.checked });
    setTimeout(() => {
      validateForm();
    });
  }}
/>;

Base on @olefrank's answer. This code work with me.

const validationSchema = Yup.object().shape({
  subject: Yup.string().required(i18n.t('required-field')),
  description: Yup.string(),
  daysOfWeek: Yup.array()
    .of(
      Yup.object().shape({
        dayOfWeek: Yup.string(),
        checked: Yup.boolean(),
      })
    )
    .compact((v) => !v.checked)
    .min(1, i18n.t('required-field')), // <– `.min(1)` instead of `.required()`
  taskSchedules: Yup.array(),
});

I have done this type of validation in my Node.js(Express.js) project. You can try validation in this way.

const validationSchema = yup.object({
  subject: yup.string().required(),
  description: yup.string().required(), 
  daysOfWeek: yup.array(
    yup.object({
      dayOfWeek: yup.string().required(),
      checked: yup.boolean().required()
    })
  )
})

If you trying in latest version it should be used like this Yup.array().min(1, "At least one option is required").required()

In my case I have used formik with yup for this,

I want to select only one value in an array if not selected I need to display the error

array =  [{"label": "Option 1", "selected": false, "value": "option-1"}, {"label": "Option 2", "selected": false, "value": "option-2"}, {"label": "Option 3", "selected": false, "value": "option-3"}]

Yup.mixed().test({
 message: 'Required',test: 
val => val.filter(i => i.selected === true).length === 1})

it worked for me

Yup.mixed().test({
 message: 'Required',test: 
val => val.filter(i => i.selected === true).length !== 0})

I did a similar validation like this. You can try this approach

const schema = yup.object().shape({
    subject: yup.string().required(),
    description: yup.string()
    daysOfWeek: yup.array().of(
      yup.lazy(value => {
        const { checked } = value // Get the value of checked field

        return checked
          ? yup.object().shape({
              dayOfWeek: yup.string().required(), // validate only if checked is true
              checked: yup.boolean()
            }) 
           : yup.object().shape({
              dayOfWeek: yup.string(),
              checked: yup.boolean()
            })
      })
    ),
    taskSchedules: yup.array()
})