fix(legacy)!: remove location.protocol!="file:" condition for modern android webview

[maliut]

Description

I'm packaging a static website generated by Vite into an Android app. I used plugin-legacy to support older Android phones. However, in modern WebViews, this causes both modern chunks and legacy chunks to be loaded, resulting in unexpected behavior.

Reproduction Steps

1. Create a new Vite project and add plugin-legacy
2. In Vite config set base: './'
3. Add a line console.log('App initializing...') in main.js to track its execution
4. Create an Android project containing only a WebView
5. Place the Vite build output in the Android project's assets folder
6. Load this HTML file in the Android WebView mWebView.loadUrl("file:///android_asset/index.html");
7. Run the Android project and check Logcat to see the console log printed twice — once from the modern chunk and once from the legacy chunk

[INFO:CONSOLE:33] "App initializing...", source: file:///android_asset/assets/index.C48xOSVJ.js (33)
[INFO:CONSOLE:19] "App initializing...", source: file:///android_asset/assets/index-legacy.CqIw3Dqg.js (19)

Root Cause

The index.html generated by Vite build contains the following code:

<script type="module" crossorigin src="./assets/index.C48xOSVJ.js"></script>
<link rel="stylesheet" crossorigin href="./assets/index.0pCfBZ4Q.css">
<script type="module">import.meta.url;import("_").catch(()=>1);(async function*(){})().next();if(location.protocol!="file:"){window.__vite_is_modern_browser=true}</script>
<script type="module">!function(){if(window.__vite_is_modern_browser)return;console.warn("vite: loading legacy chunks, syntax error above and the same error below should be ignored");var e=document.getElementById("vite-legacy-polyfill"),n=document.createElement("script");n.src=e.src,n.onload=function(){System.import(document.getElementById('vite-legacy-entry').getAttribute('data-src'))},document.body.appendChild(n)}();</script>

This means __vite_is_modern_browser is only set to true when location.protocol!="file:". As a result, even if the modern chunk loads successfully, the legacy chunk is still loaded.

Solution

This pull request essentially reverts #8524.

Determining whether a browser is modern should only depend on the browser's capabilities. There's no causal relationship between checking if the protocol is file: and whether the browser is modern.

I read the original pull request. Their core requirement was to use only legacy chunks (and skip modern chunks) in a specific scenario (in this case, when loading via the file: protocol). Now, plugin-legacy already has the renderModernChunks option to meet their needs.

[sapphi-red]

Makes sense to me.

Could you add a line to the document that tells renderModernChunks is also useful for usecases like #8524?
https://github.com/vitejs/vite/tree/9f583025499c6f2810c9f8547b62d12c27675b75/packages/plugin-legacy#rendermodernchunks

[maliut]

Thank you for review! I have updated the document. I'm not sure if my expression is accurate and concise enough, feel free to make any modifications!

[sapphi-red]

Looks good to me 👍