Properly handle nested array data in prepareDataForValidation.

[jamesremuscat]

Previously, we would always return an object even if values was an array. Now, we test to see if values is an array and set data accordingly.

I've included a test for this scenario.

Fixes #2213.

[vercel]

This pull request is being automatically deployed with ZEIT Now (learn more).
To see the status of your deployment, click below or on the icon next to each commit.

🔍 Inspect: https://zeit.co/jared/formik-docs/8d7t0h0yb
✅ Preview: https://formik-docs-git-fork-jamesremuscat-fix-2213-nested-ar-e17f42.jared.now.sh

[codesandbox-ci]

This pull request is automatically built and testable in CodeSandbox.

To see build info of the built libraries, click here or the icon next to each commit SHA.

Latest deployment of this branch, based on commit 157603a:

Sandbox	Source
Formik TypeScript Playground	Configuration

[elmarburke]

This fix didn't went in release of 2.1.4, right? I still have the issue 😢

[jamesremuscat]

@elmarburke No, it was merged just after 2.1.4 was released.

[kononenko-a-m]

hi @jaredpalmer wanted to ask, if there any plan to release this fix in 2.1.5, and is there any plan in general release 2.1.5?

[multimeric]

This is a pretty dreadful problem, since it makes nested arrays totally unusable. However I found a workaround, which is to install the CI version of Formik from just after the PR was merged: npm install https://pkg.csb.dev/jaredpalmer/formik/commit/157603ab/formik. You can also use newer builds listed on this page, but the command above seems to work okay for me.