fix: set scripts imported by HTML moduleSideEffects=true (#18411)

Author: sapphi-red

packages/vite/src/node/plugins/html.ts

@@ -108,7 +108,8 @@ export function htmlInlineProxyPlugin(config: ResolvedConfig): Plugin {
         const url = file.replace(normalizePath(config.root), '')
         const result = htmlProxyMap.get(config)!.get(url)?.[index]
         if (result) {
-          return result
+          // set moduleSideEffects to keep the module even if `treeshake.moduleSideEffects=false` is set
+          return { ...result, moduleSideEffects: true }
         } else {
           throw new Error(`No matching HTML proxy module found from ${id}`)
         }
@@ -426,6 +427,7 @@ export function buildHtmlPlugin(config: ResolvedConfig): Plugin {
           return url
         }
 
+        const setModuleSideEffectPromises: Promise<void>[] = []
         await traverseHtml(html, id, (node) => {
           if (!nodeIsElement(node)) {
             return
@@ -452,6 +454,19 @@ export function buildHtmlPlugin(config: ResolvedConfig): Plugin {
             if (isModule) {
               inlineModuleIndex++
               if (url && !isExcludedUrl(url) && !isPublicFile) {
+                setModuleSideEffectPromises.push(
+                  this.resolve(url, id)
+                    .then((resolved) => {
+                      if (!resolved) {
+                        return Promise.reject()
+                      }
+                      return this.load(resolved)
+                    })
+                    .then((mod) => {
+                      // set this to keep the module even if `treeshake.moduleSideEffects=false` is set
+                      mod.moduleSideEffects = true
+                    }),
+                )
                 // <script type="module" src="..."/>
                 // add it as an import
                 js += `\nimport ${JSON.stringify(url)}`
@@ -687,6 +702,8 @@ export function buildHtmlPlugin(config: ResolvedConfig): Plugin {
           js = `import "${modulePreloadPolyfillId}";\n${js}`
         }
 
+        await Promise.all(setModuleSideEffectPromises)
+
         // Force rollup to keep this module from being shared between other entry points.
         // If the resulting chunk is empty, it will be removed in generateBundle.
         return { code: js, moduleSideEffects: 'no-treeshake' }

packages/vite/src/node/plugins/resolve.ts

@@ -348,14 +348,7 @@ export function resolvePlugin(
           res = ensureVersionQuery(res, id, options, ssr, depsOptimizer)
           debug?.(`[relative] ${colors.cyan(id)} -> ${colors.dim(res)}`)
 
-          // If this isn't a script imported from a .html file, include side effects
-          // hints so the non-used code is properly tree-shaken during build time.
-          if (
-            !options.idOnly &&
-            !options.scan &&
-            options.isBuild &&
-            !importer?.endsWith('.html')
-          ) {
+          if (!options.idOnly && !options.scan && options.isBuild) {
             const resPkg = findNearestPackageData(
               path.dirname(res),
               options.packageCache,