fix(plugin-legacy): prevent failed to load module (#8285)

Author: sapphi-red

packages/plugin-legacy/README.md

@@ -147,8 +147,12 @@ The legacy plugin requires inline scripts for [Safari 10.1 `nomodule` fix](https
 
 - `sha256-MS6/3FCg4WjP9gwgaBGwLpRCY6fZBgwmhVCdrPrNf3E=`
 - `sha256-tQjf8gvb2ROOMapIxFvFAYBeUJ0v1HCbOcSmDNXGtDo=`
-- `sha256-4m6wOIrq/wFDmi9Xh3mFM2mwI4ik9n3TMgHk6xDtLxk=`
-- `sha256-uS7/g9fhQwNZS1f/MqYqqKv8y9hCu36IfX9XZB5L7YY=`
+- `sha256-BoFUHKsYhJ9tbsHugtNQCmnkBbZ11pcW6kZguu+T+EU=`
+- `sha256-A18HC3jLpyEc9B8oyxq/NBFCyFBJFSsRLt0gmT9kft8=`
+
+<!--
+Run `node --input-type=module -e "import {cspHashes} from '@vitejs/plugin-legacy'; console.log(cspHashes.map(h => 'sha256-'+h))"` to retrieve the value.
+-->
 
 These values (without the `sha256-` prefix) can also be retrieved via
 

packages/plugin-legacy/src/index.ts

@@ -40,7 +40,7 @@ const legacyEntryId = 'vite-legacy-entry'
 const systemJSInlineCode = `System.import(document.getElementById('${legacyEntryId}').getAttribute('data-src'))`
 
 const detectModernBrowserVarName = '__vite_is_modern_browser'
-const detectModernBrowserCode = `try{import(new URL(import.meta.url).href).catch(()=>1);}catch(e){}window.${detectModernBrowserVarName}=true;`
+const detectModernBrowserCode = `try{import.meta.url;import("_").catch(()=>1);}catch(e){}window.${detectModernBrowserVarName}=true;`
 const dynamicFallbackInlineCode = `!function(){if(window.${detectModernBrowserVarName})return;console.warn("vite: loading legacy build because dynamic import or import.meta.url is unsupported, syntax error above should be ignored");var e=document.getElementById("${legacyPolyfillId}"),n=document.createElement("script");n.src=e.src,n.onload=function(){${systemJSInlineCode}},document.body.appendChild(n)}();`
 
 const forceDynamicImportUsage = `export function __vite_legacy_guard(){import('data:text/javascript,')};`