sentryVitePlugin creates unnecessary JS modules for each index page #829

In a vite multi-page app, sentryVitePlugin causes "vite build" to emit a separate, unique, unexpected JS module for each index page.

Environment

@sentry/vite-plugin 4.6.1
vite 7.3.0

Steps to Reproduce

Here is a minimal-example.zip that reproduces the issue.

Or:

1. Create a simple vite MPA with a few index pages:

   // vite.config.js
   import {sentryVitePlugin} from "@sentry/vite-plugin";
   import {defineConfig} from "vite";
   
   export default defineConfig({
     appType: "mpa",
     build: {
       rollupOptions: {
         input: ["index.html", "page1.html", "page2.html"],
       },
     },
     plugins: [
       // Enable this to reproduce the bug:
       // sentryVitePlugin({}),
     ],
   });

   In my example, index.html has no scripts, and page1.html and page2.html both load the same shared module:

    <script type="module" src="/src/shared-module.js"></script>

   (It doesn't matter what code is in shared-module.js. The sentryVitePlugin options don't seem to affect the results, and can be empty as shown above.)

2. First run "vite build" without sentryVitePlugin and examine the output:

   % ls -1 dist/assets
   shared-module-DLkOR36O.js
   
   % grep module dist/*.html
   dist/page1.html:  <script type="module" crossorigin src="/assets/shared-module-DLkOR36O.js"></script>
   dist/page2.html:  <script type="module" crossorigin src="/assets/shared-module-DLkOR36O.js"></script>

3. Uncomment the sentryVitePlugin in vite.config.js and repeat the "vite build". Compare the output:

   % ls -1 dist/assets
   index-CrvgSmxQ.js
   page1-DOS8u50U.js
   page2-DOS8u50U.js
   shared-module-B_F8-UTR.js
   
   % grep module dist/*.html
   dist/index.html:  <script async type="module" crossorigin src="/assets/index-CrvgSmxQ.js"></script>
   dist/page1.html:  <script type="module" crossorigin src="/assets/page1-DOS8u50U.js"></script>
   dist/page1.html:  <link rel="modulepreload" crossorigin href="/assets/shared-module-B_F8-UTR.js">
   dist/page2.html:  <script type="module" crossorigin src="/assets/page2-DOS8u50U.js"></script>
   dist/page2.html:  <link rel="modulepreload" crossorigin href="/assets/shared-module-B_F8-UTR.js">

Expected Result

The sentryVitePlugin should add metadata to generated modules (like shared-module-[hash].js in the example), but should not rework the import graph, create new modules, or add script tags to pages that didn't have them in the first place.

Actual Result

A unique module is generated for every html page in rollup.options.input. Pages that had been sharing modules will instead load a page-specific module that imports the shared code. Pages that didn't contain any scripts will now have one.

These unnecessary scripts slow page loading and interfere with caching.