Bug report. I think.
dirtyFieldsSinceLastSubmit is always undefined, but dirtySinceLastSubmit returns the expected boolean value.
dirtyFieldsSinceLastSubmit should be an object full of booleans, with a value of true for each field that has a different value from the one when the form was last submitted.
https://final-form.org/docs/react-final-form/examples/submission-errors
I don't have a sandbox set up. If you add dirtyFieldsSinceLastSubmit to the destructured arguments in the render prop function and console.log it within that same function, it will always return undefined, even after a submission.
RFF 6.3.3
FF 4.18.5
Node 10.15.3
Trying to get an understanding of this also, here is my forked example where we are just rendering out the rest of the props available... https://codesandbox.io/s/crazy-hermann-vow92?fontsize=14&hidenavigation=1&theme=dark

@erikras - any ideas, here is the docs... https://final-form.org/docs/final-form/types/FormState#dirtyfieldssincelastsubmit
Looks like it has been added to master, just need a version bump https://github.com/final-form/react-final-form/pull/688/files
Thanks, @ianqueue. @erikras, when can we expect the next release?
@erikras - any plans on the next patch/minor release? This feature is in the documentation but absent from the latest release and is now in master. thanks.
@erikras Do you have any plans for release this fix?
Looks like this was just fixed in 6.3.4
Looks like this was just fixed in 6.3.4
Yes, you are right
Upgrade to RFF 6.3.4 and FF 4.18.7 resolves the issue.
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@erikras - any plans on the next patch/minor release? This feature is in the documentation but absent from the latest release and is now in master. thanks.