Add comments clarifying why getInitialProps wrapper is imported directly

Author: Luca Forstner

packages/nextjs/src/config/loaders/dataFetchersLoader.ts

@@ -128,6 +128,9 @@ export default function wrapDataFetchersLoader(this: LoaderThis<LoaderOptions>,
     }
 
     if (hasDefaultExport(ast)) {
+      // We don't import the `withSentryGetInitialProps` wrapper from `@sentry/nextjs` since `getInitialProps` can run
+      // on both the server and the client and we don't want to have side effects from the server SDK on the client and
+      // vice versa. By importing the loader directly we avoid the side effects.
       outputFileContent += `
         import { default as _sentry_default } from "${this.resourcePath}?sentry-proxy-loader";
         import { withSentryGetInitialProps } from "@sentry/nextjs/build/esm/config/wrappers";

packages/nextjs/src/config/wrappers/index.ts

@@ -2,3 +2,7 @@ export { withSentryGetStaticPaths } from './withSentryGetStaticPaths';
 export { withSentryGetStaticProps } from './withSentryGetStaticProps';
 export { withSentryGetInitialProps } from './withSentryGetInitialProps';
 export { withSentryGetServerSideProps } from './withSentryGetServerSideProps';
+
+// Disclaimer: Keep this file side-effect free. If you have to intruduce a side-effect, make sure it can run on the
+// browser and on the server. Reason: Our `getInitialProps` wrapper imports this file and `getInitialProps` might run on
+// the browser and / or on the server.

packages/nextjs/src/config/wrappers/withSentryGetInitialProps.ts

@@ -1,5 +1,9 @@
 import { GIProps } from './types';
 
+// Disclaimer: Keep this file side-effect free. If you have to intruduce a side-effect, make sure it can run on the
+// browser and on the server. Reason: This `getInitialProps` wrapper imports this file and `getInitialProps` might run on
+// the browser and / or on the server.
+
 /**
  * Create a wrapped version of the user's exported `getInitialProps` function
  *