fix(plugin-legacy): always fallback legacy build when CSP (#6535)

packages/plugin-legacy/README.md

@@ -165,7 +165,9 @@ The legacy plugin requires inline scripts for [Safari 10.1 `nomodule` fix](https
 
 - `sha256-MS6/3FCg4WjP9gwgaBGwLpRCY6fZBgwmhVCdrPrNf3E=`
 - `sha256-tQjf8gvb2ROOMapIxFvFAYBeUJ0v1HCbOcSmDNXGtDo=`
-- `sha256-T9h4ixy0FtNsCwAyTfBtIY6uV5ZhMeNQIlL42GAKEME=`
+- `sha256-xYj09txJ9OsgySe5ommpqul6FiaJZRrwe3KTD7wbV6w=`
+- `sha256-4m6wOIrq/wFDmi9Xh3mFM2mwI4ik9n3TMgHk6xDtLxk=`
+- `sha256-uS7/g9fhQwNZS1f/MqYqqKv8y9hCu36IfX9XZB5L7YY=`
 
 These values (without the `sha256-` prefix) can also be retrieved via
 

packages/plugin-legacy/index.js

@@ -18,7 +18,11 @@ const safari10NoModuleFix = `!function(){var e=document,t=e.createElement("scrip
 const legacyPolyfillId = 'vite-legacy-polyfill'
 const legacyEntryId = 'vite-legacy-entry'
 const systemJSInlineCode = `System.import(document.getElementById('${legacyEntryId}').getAttribute('data-src'))`
-const dynamicFallbackInlineCode = `!function(){try{new Function("m","return import(m)")}catch(o){console.warn("vite: loading legacy build because dynamic import is unsupported, syntax error above should be ignored");var e=document.getElementById("${legacyPolyfillId}"),n=document.createElement("script");n.src=e.src,n.onload=function(){${systemJSInlineCode}},document.body.appendChild(n)}}();`
+
+const detectDynamicImportVarName = '__vite_is_dynamic_import_support'
+const detectDynamicImportVarInitCode = `var ${detectDynamicImportVarName}=false;`
+const detectDynamicImportCode = `try{import("_").catch(()=>1);}catch(e){}window.${detectDynamicImportVarName}=true;`
+const dynamicFallbackInlineCode = `!function(){if(window.${detectDynamicImportVarName})return;console.warn("vite: loading legacy build because dynamic import is unsupported, syntax error above should be ignored");var e=document.getElementById("${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,')};`
 
@@ -430,6 +434,18 @@ function viteLegacyPlugin(options = {}) {
 
       // 5. inject dynamic import fallback entry
       if (genDynamicFallback && legacyPolyfillFilename && legacyEntryFilename) {
+        tags.push({
+          tag: 'script',
+          attrs: { type: 'module' },
+          children: detectDynamicImportVarInitCode,
+          injectTo: 'head'
+        })
+        tags.push({
+          tag: 'script',
+          attrs: { type: 'module' },
+          children: detectDynamicImportCode,
+          injectTo: 'head'
+        })
         tags.push({
           tag: 'script',
           attrs: { type: 'module' },
@@ -695,5 +711,7 @@ viteLegacyPlugin.default = viteLegacyPlugin
 viteLegacyPlugin.cspHashes = [
   createHash('sha256').update(safari10NoModuleFix).digest('base64'),
   createHash('sha256').update(systemJSInlineCode).digest('base64'),
+  createHash('sha256').update(detectDynamicImportVarInitCode).digest('base64'),
+  createHash('sha256').update(detectDynamicImportCode).digest('base64'),
   createHash('sha256').update(dynamicFallbackInlineCode).digest('base64')
 ]