Run validationSchema for validateField calls

[jamesmosier]

Previously validateField would only work with a validate={Function} property on a field. Now you can perform validateField('myFieldName') and it will look at the provided validationSchema to determine any errors.

Fixes issue #1755

[michielmetcake]

I would love to see this merged 🙌🏻

[johnrom]

Some thoughts on design patterns.

[johnrom]

I think it'd be more readable to continue with positive checks and to return the resolved promise last.

if (isFunction(props.validate)) {
  // ...
} else if (props.validationSchema) { /* validation code*/ } 

return Promise.resolve();

Also, if in combination with my next review comment about validating a single field, we can have their callbacks match, we can combine these into a single if (maybePromise) { /* validate */ }

[jamesmosier]

Thanks for the comments @johnrom - I'll try to get to these this weekend or next week!

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[jaredpalmer]

@johnrom are you good with this?

[JFGagnon]

@johnrom @jaredpalmer when can we expect this PR to be merged?

[johnrom]

In terms of validating a single field, I realized that a change might actually invalidate a different field, so my review can be disregarded. I don't use validation schema in my projects, so if you guys are good with it and have tested, feel free to move forward without my signoff!

I might recommend adding a test though, to prevent future regressions.

[jamesmosier]

@johnrom I can fix the conflicts, add some tests, and also make some of the changes you suggested (such as “I think it’d be more readable to continue with positive checks and to return the resolved promise last...“. which is still relevant).

Thanks for following up!

[jaredpalmer]

Okay, update and I will merge

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[jamesmosier]

@jaredpalmer updated it with some tests & rearranged some logic

[jaredpalmer]

Cool. LGTM