perf: avoid side effects resolving in dev and in the optimizer/scanner

packages/vite/src/node/config.ts

@@ -594,6 +594,7 @@ export async function resolveConfig(
                 preferRelative: false,
                 tryIndex: true,
                 ...options,
+                idOnly: true,
               }),
             ],
           }))

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

@@ -115,6 +115,13 @@ export interface InternalResolveOptions extends Required<ResolveOptions> {
   // Resolve using esbuild deps optimization
   getDepsOptimizer?: (ssr: boolean) => DepsOptimizer | undefined
   shouldExternalize?: (id: string) => boolean | undefined
+
+  /**
+   * Set by createResolver, we only care about the resolved id. moduleSideEffects
+   * and other fields are discarded so we can avoid computing them.
+   * @internal
+   */
+  idOnly?: boolean
 }
 
 export function resolvePlugin(resolveOptions: InternalResolveOptions): Plugin {
@@ -265,7 +272,12 @@ export function resolvePlugin(resolveOptions: InternalResolveOptions): Plugin {
 
           // 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 (!importer?.endsWith('.html')) {
+          if (
+            !options.idOnly &&
+            !options.scan &&
+            options.isBuild &&
+            !importer?.endsWith('.html')
+          ) {
             const resPkg = findNearestPackageData(
               path.dirname(res),
               options.packageCache,
@@ -302,10 +314,12 @@ export function resolvePlugin(resolveOptions: InternalResolveOptions): Plugin {
 
       // external
       if (isExternalUrl(id)) {
-        return {
-          id,
-          external: true,
-        }
+        return options.idOnly
+          ? id
+          : {
+              id,
+              external: true,
+            }
       }
 
       // data uri: pass through (this only happens during build and will be
@@ -377,10 +391,12 @@ export function resolvePlugin(resolveOptions: InternalResolveOptions): Plugin {
               this.error(message)
             }
 
-            return {
-              id,
-              external: true,
-            }
+            return options.idOnly
+              ? id
+              : {
+                  id,
+                  external: true,
+                }
           } else {
             if (!asSrc) {
               debug?.(
@@ -773,7 +789,10 @@ export function tryNodeResolve(
     return { ...resolved, id: resolvedId, external: true }
   }
 
-  if ((isBuild && !depsOptimizer) || externalize) {
+  if (
+    !options.idOnly &&
+    ((!options.scan && isBuild && !depsOptimizer) || externalize)
+  ) {
     // Resolve package side effects for build so that rollup can better
     // perform tree-shaking
     return processResult({
@@ -853,7 +872,7 @@ export function tryNodeResolve(
     resolved = depsOptimizer!.getOptimizedDepId(optimizedInfo)
   }
 
-  if (isBuild) {
+  if (!options.idOnly && !options.scan && isBuild) {
     // Resolve package side effects for build so that rollup can better
     // perform tree-shaking
     return {
@@ -1210,16 +1229,22 @@ function tryResolveBrowserMapping(
           : tryFsResolve(path.join(pkg.dir, browserMappedPath), options))
       ) {
         debug?.(`[browser mapped] ${colors.cyan(id)} -> ${colors.dim(res)}`)
-        const resPkg = findNearestPackageData(
-          path.dirname(res),
-          options.packageCache,
-        )
-        const result = resPkg
-          ? {
+        let result: PartialResolvedId = { id: res }
+        if (options.idOnly) {
+          return result
+        }
+        if (!options.scan && options.isBuild) {
+          const resPkg = findNearestPackageData(
+            path.dirname(res),
+            options.packageCache,
+          )
+          if (resPkg) {
+            result = {
               id: res,
               moduleSideEffects: resPkg.hasSideEffects(res),
             }
-          : { id: res }
+          }
+        }
         return externalize ? { ...result, external: true } : result
       }
     } else if (browserMappedPath === false) {