feat: remake first measure logic to not use a static member (#288)

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# Summary

First render (or rather render without an accessible Component View)
used a mock component view for measurements as a static member of the
Shadow Node. For obvious reasons this won't work with multiple inputs on
the same screen.
Original motivation for having mock as a member was to have it created
as soon as possible (Shadow Node constructor) to make sure it can be
measured on the first render. Turns out it can be very well created just
when needed (as long as on main thread) without any first render
performance losses.
This PR remakes and simplifies this approach so that we don't need a
static member anymore.

## Test Plan

Run iOS example app and add a simple state to conditionally render the
component. Record its first renders and notice it still properly is
rendered with the proper height at once, no stutters or jumps.

## Screenshots / Videos

--

## Compatibility

| OS      | Implemented |
| ------- | :---------: |
| iOS     |    ✅    |
| Android |   ❌     |

Author: szydlovsky

ios/internals/EnrichedTextInputViewShadowNode.h

@@ -35,8 +35,7 @@ class EnrichedTextInputViewShadowNode : public ConcreteViewShadowNode<
 
     private:
     int localForceHeightRecalculationCounter_;
-    static id mockTextInputView_;
-    void setupMockTextInputView_();
+    id setupMockTextInputView_() const;
 };
 
 } // namespace facebook::react

ios/internals/EnrichedTextInputViewShadowNode.mm

@@ -8,34 +8,25 @@
 namespace facebook::react {
 
 extern const char EnrichedTextInputViewComponentName[] = "EnrichedTextInputView";
-id EnrichedTextInputViewShadowNode::mockTextInputView_ = nullptr;
 
 EnrichedTextInputViewShadowNode::EnrichedTextInputViewShadowNode(
   const ShadowNodeFragment& fragment,
   const ShadowNodeFamily::Shared& family,
   ShadowNodeTraits traits
 ): ConcreteViewShadowNode(fragment, family, traits) {
   localForceHeightRecalculationCounter_ = 0;
-  
-  // mock text input needs to be initialized on the main thread
-  if([NSThread isMainThread]) {
-    setupMockTextInputView_();
-  } else {
-    dispatch_sync(dispatch_get_main_queue(), ^{
-      setupMockTextInputView_();
-    });
-  }
 }
 
 // mock input is used for the first measure calls that need to be done when the real input isn't defined yet
-void EnrichedTextInputViewShadowNode::setupMockTextInputView_() {
+id EnrichedTextInputViewShadowNode::setupMockTextInputView_() const {
   // it's rendered far away from the viewport
   const int veryFarAway = 20000;
   const int mockSize = 1000;
-  mockTextInputView_ = [[EnrichedTextInputView alloc] initWithFrame:(CGRectMake(veryFarAway, veryFarAway, mockSize, mockSize))];
+  EnrichedTextInputView *mockTextInputView_ = [[EnrichedTextInputView alloc] initWithFrame:(CGRectMake(veryFarAway, veryFarAway, mockSize, mockSize))];
   const auto props = this->getProps();
-  ((EnrichedTextInputView *)mockTextInputView_)->blockEmitting = YES;
+  mockTextInputView_->blockEmitting = YES;
   [mockTextInputView_ updateProps:props oldProps:nullptr];
+  return mockTextInputView_;
 }
 
 EnrichedTextInputViewShadowNode::EnrichedTextInputViewShadowNode(
@@ -65,11 +56,6 @@
     EnrichedTextInputView *typedComponentObject = (EnrichedTextInputView *) componentObject;
 
     if(typedComponentObject != nullptr) {
-      // remove the mock input on the first render with a defined real input
-      if(mockTextInputView_ != nullptr) {
-        mockTextInputView_ = nullptr;
-      }
-    
       __block CGSize estimatedSize;
 
       // synchronously dispatch to main thread if needed
@@ -87,18 +73,16 @@
       };
     }
   } else {
-    if(mockTextInputView_ == nullptr) {
-      return Size();
-    }
-  
     __block CGSize estimatedSize;
 
     // synchronously dispatch to main thread if needed
     if([NSThread isMainThread]) {
-      estimatedSize = [mockTextInputView_ measureSize:layoutConstraints.maximumSize.width];
+      EnrichedTextInputView *mockTextInputView = setupMockTextInputView_();
+      estimatedSize = [mockTextInputView measureSize:layoutConstraints.maximumSize.width];
     } else {
       dispatch_sync(dispatch_get_main_queue(), ^{
-        estimatedSize = [mockTextInputView_ measureSize:layoutConstraints.maximumSize.width];
+        EnrichedTextInputView *mockTextInputView = setupMockTextInputView_();
+        estimatedSize = [mockTextInputView measureSize:layoutConstraints.maximumSize.width];
       });
     }