Revert preserve Platform.select initializers (#58541)

Summary:
Pull Request resolved: #58541

Reverts #58350, restoring the
long-standing `Platform.select` inlining behavior.

Per robhogan and vonovak:

Metro has inlined Platform.select() (in release builds only, not configurable) forever really - it goes back to at least 2017, before the start of the Metro repo, eg: react/metro@a317b9d It's always had that behaviour where it collapses side-effects of inactive branches.

Recently, the plugin was copied/re-implemented into RN.

Right now (RN 0.88, Metro 0.87) they both have their own version of the plugin and Metro's runs after RN's, but Metro's shouldn't find anything left to inline and should be a no-op. I couldn't remove it from Metro immediately only because it'd need a major Metro release, but I plan to remove it soon.

So RN's is effectively a continuation of Metro's 8 year old behaviour - we just moved the implementation.

Changelog:
[General][Fixed] - Restore long-standing Platform.select inlining behavior that collapses side effects of inactive branches

See discussion: #58442

Reviewed By: javache

Differential Revision: D120147924

fbshipit-source-id: 0ec9cc7f8eade4e6276d0e049bc5fedfc613017f

Author: vzaidman

packages/react-native-babel-preset/src/__tests__/inline-platform-plugin-test.js

@@ -483,25 +483,6 @@ describe('Platform.select', () => {
     expect(select('{ios: 1, ios: 2}')).toContain('const value=2');
   });
 
-  test('does not discard impure initializers', () => {
-    expectUnchanged(`
-      const value = require('react-native').Platform.select({
-        ios: first(),
-        android: android(),
-        ios: last(),
-      });
-    `);
-  });
-
-  test('does not mutate object methods when bailing out on impure initializers', () => {
-    expectUnchanged(`
-      const value = require('react-native').Platform.select({
-        ios() { return 1; },
-        android: sideEffect(),
-      });
-    `);
-  });
-
   test('does not inline computed keys', () => {
     expect(select('{[key]: 1, default: 2}')).toContain('Platform.select');
   });

packages/react-native-babel-preset/src/inline-platform-plugin.js

@@ -443,9 +443,7 @@ module.exports = function inlinePlatformPlugin(
         if (t.isObjectProperty(property)) {
           return property.value;
         }
-        // Clone: toExpression mutates in place, e.g. `ios() {}` would be
-        // left mutated if the purity check below bails out.
-        return t.toExpression(t.cloneNode(property));
+        return t.toExpression(property);
       }
     }
     return fallback();
@@ -522,25 +520,13 @@ module.exports = function inlinePlatformPlugin(
           return;
         }
 
-        const replacement = findProperty(spec, platform, () =>
-          findProperty(spec, 'native', () =>
-            findProperty(spec, 'default', () => t.identifier('undefined')),
+        path.replaceWith(
+          findProperty(spec, platform, () =>
+            findProperty(spec, 'native', () =>
+              findProperty(spec, 'default', () => t.identifier('undefined')),
+            ),
           ),
         );
-        // Inlining must not drop side effects from discarded property values.
-        // Assess the property itself: an ObjectMethod has no `.value`, so
-        // checking `property.value` would wrongly treat every method as
-        // impure and skip inlining.
-        if (
-          spec.properties.every(
-            property =>
-              (t.isObjectProperty(property) &&
-                property.value === replacement) ||
-              path.scope.isPure(property),
-          )
-        ) {
-          path.replaceWith(replacement);
-        }
       },
     },
   };