when and test stopped working together

[Sinled]

Describe the bug
After migrating to yup v1.4 when and test stopped working together, worked fine in 0.32.11.

To Reproduce

Codesanbox removed ability to run tests, https://codesandbox.io/docs/learn/sandboxes/faq#where-can-i-find-the-tests-tab, so I am not sure where to add runnable test

But here simplified code and test example that worked in previous versions of yup:

Code here

import { object, mixed, string } from 'yup';
import { it, expect } from 'vitest';

const schema = object().shape({
    value: mixed<string | number>()
        .label('Value')
        .required()
        .when('$model.isStringValueType', {
            is: true,
            then: () => string().required(),
        })
        .test('is-unique-value', 'Value should be unique', function (newValue) {
            if (!newValue) {
                return true;
            }

            const values = this.parent.siblingValues.filter(({ otherValue }: { otherValue: string | number }) => {
                return otherValue === newValue;
            });

            return values.length === 1;
        }),
});

it('should be invalid if "when" is not entered', async () => {
    await expect(
        schema.isValid(
            {
                siblingValues: [{ otherValue: 'foo' }, { otherValue: 'foo' }],
                value: 'foo',
            },
            { context: { model: { isStringValueType: false } } },
        ),
    ).resolves.toBe(false);
});

it('should be invalid if not a string', async () => {
    await expect(
        schema.isValid(
            {
                siblingValues: [{ otherValue: 'foo' }],
                value: 1,
            },
            { context: { model: { isStringValueType: true } } },
        ),
    ).resolves.toBe(false);
});

it('should be invalid if "when" is entered and has similar siblings', async () => {
    await expect(
        schema.isValid(
            {
                siblingValues: [{ otherValue: 'foo' }, { otherValue: 'foo' }],
                value: 'foo',
            },
            { context: { model: { isStringValueType: true } } },
        ),
    ).resolves.toBe(false);
});

At the moment, 2nd and 3rd test fails.

Expected behavior
tests should pass, both .when and .test branches should be checked

Platform (please complete the following information):

• Browser agnostic

Additional context
This is recreation of #2179

[jquense]

This is happening because your when is discarding the current schema and returning a fresh one without your custom test:

.when('$model.isStringValueType', {
    is: true,
-    then: () => string().required(),
+    then: schema => schema.required(),
})

[Sinled]

@jquense thanks for reply, but what should I do if I need to return different schemas? e.g. string or number depending on condition?

It worked fine before, it is not very clear what to do now.

[jquense]

Switching types isn't really supported, it didn't work fine before, it was very inconsistent and often produced broken schema which is why it was removed. You are welcome to return a brand new schema still, but it won't be automatically concated with the old one. You can approximate the old behavior by doing the concat yourself, schema=> schema.concat(string().whatever())