[metro-transform-plugins] Function calls prefixed with void together with optional chain (?.) are skipped on production (dev: false).

[Gamote]

As the title suggests, today we found out that the constant-folding-plugin replaces this call void foo?.(); with undefined; on production (dev: false).

We found this issue while using Expo SDK 50 in production mode. In development mode works just fine because the constant-folding-plugin is skipped. For more information and a MRE please see this issue expo/expo#26276.

After some investigation we found out that we can fix this by adding OptionalCallExpression: unsafe in the evaluate method of the plugin. I am not 100% that this is the way to go as I don't have a lot of experience with Babel plugins and I might miss important implications. Please let me know if you have some guidance and I will be more than happy to proceed with a PR.

Here is the diff that solved my problem:

diff --git a/node_modules/metro-transform-plugins/src/constant-folding-plugin.js b/node_modules/metro-transform-plugins/src/constant-folding-plugin.js
index d0dd8ac..f1e96c6 100644
--- a/node_modules/metro-transform-plugins/src/constant-folding-plugin.js
+++ b/node_modules/metro-transform-plugins/src/constant-folding-plugin.js
@@ -27,8 +27,15 @@ function constantFoldingPlugin(context) {
     };
     path.traverse(
       {
-        CallExpression: unsafe,
         AssignmentExpression: unsafe,
+        CallExpression: unsafe,
+        /**
+         * This will mark `foo?.()` as unsafe, so it is not replaced with `undefined` down the line.
+         *
+         * We saw this case in the wild, where the unary expression `void foo?.()` was replaced with `undefined`
+         * resulting in the expression call being skipped.
+         */
+        OptionalCallExpression: unsafe,
       },
       state
     );

[Gamote]

I have started a PR, hopefully it is the right direction: #1178.