feat: prevent flattening style arrays

[jpudysz]

Summary

Why

While integrating Unistyles with Reanimated, there is one clash that I would love to resolve.
We encourage developers to merge styles using array syntax, as it makes it easier to detect the order of merging and persist the C++ state attached to styles.

Reanimated flattens arrays passed to the style prop, making it impossible to distinguish which props are animated and which are provided by Unistyles.

How

To fix this, we just need to remove two one occurrences of array flattening. I tested it locally with Unistyles, and I can correctly retrieve the style prop as-is.

Unistyles have to retrieve ref + style prop while borrowing ref.

Additionally, with this change, I can treat Reanimated styles as inline styles. Since inline styles are not processed by Unistyles algorithm, this can completely eliminate issues such as preventing animations when switching themes or changing device orientation.

Test plan

I tested it locally and I'm happy with the outcome. But I do understand that you have own test suites and regression tests, so I hope this won't break anything.

[jpudysz]

Added one more check for objects

[jeremybarbet]

I tried to apply the changes locally and had some styles not being applied anymore. Since the flattenArray is recursively going through the array of styles, I believe I have more than one-depth level on my array.

However, I tried with the following:

// Kept as before
const styles = flattenArray<StyleProps>(styleProp ?? []);

// Only apply this change
props[key] = processedStyle;

And I didn't have any warning anymore, and the regression I saw previously didn't happen in this case. Did you try that too?

[jpudysz]

I believe I have more than one-depth level on my array

Yeah, but is array of arrays a valid style? Reanimated was safeguarding for it and that's all. Maybe we can call flat. I need to give it a try.

[jpudysz]

@jeremybarbet nevertheless you're right! It's just a one liner and I can still get Array on my side. Thanks for the verification 🙏🏼 I will update PR.

[jpudysz]

I updated few tests to indicate that we may have style arrays now

[jpudysz]

I think these warnings are not from my PR. I didn't use any or touch these files. 🤔

[piaskowyk]

I've tested it, and it looks good 👍

[piaskowyk]

To fix CI run:

cd packages/react-native-reanimated && yarn formatter

then we can merge it 😄

[piaskowyk]

Dziękuję serdecznie 😊 🫡