Transform class static blocks in the Babel preset

packages/react-native-babel-preset/package.json

@@ -36,6 +36,7 @@
     "@babel/plugin-transform-async-to-generator": "^7.24.7",
     "@babel/plugin-transform-block-scoping": "^7.25.0",
     "@babel/plugin-transform-class-properties": "^7.25.4",
+    "@babel/plugin-transform-class-static-block": "^7.26.0",
     "@babel/plugin-transform-classes": "^7.25.4",
     "@babel/plugin-transform-destructuring": "^7.24.8",
     "@babel/plugin-transform-flow-strip-types": "^7.25.2",

packages/react-native-babel-preset/src/__tests__/transform-snapshot-test.js

@@ -568,6 +568,84 @@ describe('react-native-babel-preset transform snapshots', () => {
       expect(result).toContain('_classPrivateFieldLooseKey');
     });
 
+    it('transforms class static blocks without unstable_preserveClassPrivate', () => {
+      const code = `
+        class Config {
+          static value = 0;
+          static {
+            Config.value = 2;
+          }
+        }
+      `;
+      const result = transformCode(code, {
+        dev: false,
+        unstable_transformProfile: 'hermes-stable',
+      });
+      expect(result).not.toContain('static {');
+      expect(result).toContain('Config.value = 2');
+    });
+
+    it('transforms class static blocks when the profile lowers classes', () => {
+      const code = `
+        class Config {
+          static value = 0;
+          static {
+            Config.value = 2;
+          }
+        }
+      `;
+      const result = transformCode(code, {
+        dev: false,
+        unstable_transformProfile: 'hermes-legacy',
+        customTransformOptions: {
+          unstable_preserveClassPrivate: true,
+        },
+      });
+      expect(result).not.toContain('static {');
+      expect(result).toContain('Config.value = 2');
+    });
+
+    it('transforms class static blocks that use private fields and super', () => {
+      const code = `
+        class Base {
+          static base = 1;
+        }
+        class Config extends Base {
+          static #secret = 1;
+          static value = 0;
+          static {
+            Config.value = Config.#secret + super.base;
+          }
+        }
+      `;
+      const result = transformCode(code, {
+        dev: false,
+        unstable_transformProfile: 'hermes-stable',
+      });
+      expect(result).not.toContain('static {');
+      expect(result).not.toContain('#secret');
+    });
+
+    it('preserves class static blocks with unstable_preserveClassPrivate', () => {
+      const code = `
+        class Config {
+          static #secret = 1;
+          static {
+            Config.value = Config.#secret;
+          }
+        }
+      `;
+      const result = transformCode(code, {
+        dev: false,
+        unstable_transformProfile: 'hermes-stable',
+        customTransformOptions: {
+          unstable_preserveClassPrivate: true,
+        },
+      });
+      expect(result).toContain('static {');
+      expect(result).toContain('#secret');
+    });
+
     it('preserves async/await with unstable_preserveAsync', () => {
       const code = `
         async function fetchData() {

packages/react-native-babel-preset/src/configs/main.js

@@ -280,6 +280,7 @@ const getPreset = (src, options, babel) => {
           ...(preserveClassPrivate
             ? []
             : [
+                [require('@babel/plugin-transform-class-static-block')],
                 [require('@babel/plugin-transform-private-methods'), {loose}],
                 [
                   require('@babel/plugin-transform-private-property-in-object'),