Fixed FieldArray re-render on every change when subscription is empty…

[jdimovska]

Hey,

This PR fixes #93
I created a test where we pass an empty subscription object to the FieldArray and we check if only the Field whose value has changed gets re-rendered.
The test passes with this fix.

[codecov]

Codecov Report

Merging #100 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master   #100   +/-   ##
=====================================
  Coverage     100%   100%           
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  Files           6      6           
  Lines          57     60    +3     
  Branches       10     10           
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+ Hits           57     60    +3

Impacted Files	Coverage Δ
src/useFieldArray.js	100% <ø> (ø)	⬆️
src/testUtils.js	100% <100%> (ø)	⬆️

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[erikras]

Seems like this is going to necessarily break the value API... #96

Well, I guess if you provide a subscription prop and don't include value, then you don't get the value...?

[oliverlaz]

Hi @erikras, Hi @jdimovska,

I had a look at the linked issue and the provided fix.
With these changes, value subscription is disabled by default on empty object subscription.
Edit: On a second thought, Isn't this the expected behavior? Shouldn't subscription={{}} mean no-subscription?

Maybe an alternative approach would be to let the defaults (value, length) be overridden by the subscription prop on <FieldArray />

<FieldArray subscription={{ value: false }} />

In order this approach to work, this code should be changed from:
subscription: { ...subscription, value: true, length: true }, to
subscription: { value: true, length: true, ...subscription }.

With this change, all existing tests together with the new one pass successfully.
This change should be backwards compatible and shouldn't cause any side-effects if this library is used as recommended. However, it would be good if it is mentioned in the docs.

What are your thoughts on this?

[callmeberzerker]

Hi all,

subscription={{}} is definitely how ReactFinalForm interprets "no subscription" on the Form component. It makes sense for the same rule to apply here.

This will help greatly with optimizing large form sections (represented with field arrays) which are unrelated to each other.

[erikras]

Published in v3.1.1.