Use form.getState() directly instead of using subscriptions.

[BowlingX]

Hi :),

I was running into timing issues on async error handling (with final-form 4.18.6 and react-final-form 6.3.3). (The promise in onSubmit would resolve before / at the same time the subscription callback fires and would compare against a stale state. I'm not sure why the subscription is needed because we have access to the form state directly with getState().

This pull request adresses the issue of a potential stale state.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (c26b46e) to head (56dee29).
⚠️ Report is 7 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##            master       #16   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            5         5           
  Lines           44        40    -4     
  Branches        11        11           
=========================================
- Hits            44        40    -4     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[BowlingX]

Any more information required to have this merged? :)

[TylerRick]

I like how this simplifies things. Any reason we shouldn't merge this, @erikras?

[mishaberezin]

@erikras Could you please give some feedback on this issue. We're having the same problem in our projects and have to use fork of this library with similar patch applied.