javascript Single input field of rollupOptions in vite causing 404 block

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A 404 error when using rollupOptions in Vite typically means that the Rollup configuration is misconfigured, resulting in incorrect paths being generated for assets or modules. Let’s troubleshoot and resolve this issue.


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Possible Causes

1. Incorrect output.entryFileNames or output.assetFileNames in rollupOptions: Customizing the output filenames improperly can result in files not being found or served.


2. Missing assets during build: If assets are moved or renamed incorrectly, the browser may not find them.


3. Incorrect paths in your code: The build process might produce paths that don’t match the structure of the output files.


4. Improper Vite base configuration: If the base option in Vite is not set correctly, it can cause 404 errors.




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Fixes for rollupOptions

Here’s how you can configure the rollupOptions properly in vite.config.js:

Example vite.config.js:

import { defineConfig } from 'vite';



export default defineConfig({

  build: {

    rollupOptions: {

      output: {

        // Customize the output filenames for JavaScript files

        entryFileNames: 'assets/[name].[hash].js',

        chunkFileNames: 'assets/[name].[hash].js',

        assetFileNames: 'assets/[name].[hash].[ext]', // For other assets like images, CSS, etc.

      }

    },

    // Ensure correct base path if the app is not deployed at root

    base: '/',

  }

});

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Troubleshooting Steps

1. Verify Output Paths: Ensure that the custom file names in rollupOptions.output match your file structure. For instance:

Use assets/[name].[hash].js for JavaScript files.

Use assets/[name].[hash].[ext] for other assets.



2. Check the base Option: If your app is deployed to a subdirectory (e.g., /subdir), set the base option accordingly in vite.config.js:

base: '/subdir/',

3. Check the Dev Server: During development (vite dev), Vite serves files from memory, not the output directory. Make sure there are no absolute paths pointing to dist/ or other incorrect directories.


4. Clear Browser Cache: A cached version of your application may not match the current build output.


5. Inspect Generated Files: After building the app, inspect the dist/ directory. Confirm that the files match the paths being requested by the browser.


6. Analyze 404 Errors in Network Tab: Use the browser’s developer tools to check which files are causing the 404 errors. Compare the paths being requested with the actual paths in dist/.




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Example with base Option for Subdirectory Deployment

If you’re deploying to a subdirectory (e.g., https://example.com/app/), use:

export default defineConfig({

  base: '/app/',

  build: {

    rollupOptions: {

      output: {

        entryFileNames: 'assets/[name].[hash].js',

        chunkFileNames: 'assets/[name].[hash].js',

        assetFileNames: 'assets/[name].[hash].[ext]',

      }

    }

  }

});

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Debugging Commands

Run the following commands to debug:

1. Preview the Build:

npm run build

npm run preview

This serves the build locally and helps verify if the issue persists.


2. Analyze the Build Output:

vite build --mode development --debug

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Final Checklist

Custom Rollup Output: Ensure rollupOptions.output generates valid paths.

Base Path: Match the deployment base path in vite.config.js.

Correct Imports: Use relative imports (./) for files within the app.

Static Assets: Place static assets in the public/ folder for correct serving.