fix: build.modulePreload.resolveDependencies is optimizable (#16083)

Author: sapphi-red

docs/config/build-options.md

@@ -41,12 +41,13 @@ type ResolveModulePreloadDependenciesFn = (
   url: string,
   deps: string[],
   context: {
-    importer: string
+    hostId: string
+    hostType: 'html' | 'js'
   },
 ) => string[]
 ```
 
-The `resolveDependencies` function will be called for each dynamic import with a list of the chunks it depends on, and it will also be called for each chunk imported in entry HTML files. A new dependencies array can be returned with these filtered or more dependencies injected, and their paths modified. The `deps` paths are relative to the `build.outDir`. Returning a relative path to the `hostId` for `hostType === 'js'` is allowed, in which case `new URL(dep, import.meta.url)` is used to get an absolute path when injecting this module preload in the HTML head.
+The `resolveDependencies` function will be called for each dynamic import with a list of the chunks it depends on, and it will also be called for each chunk imported in entry HTML files. A new dependencies array can be returned with these filtered or more dependencies injected, and their paths modified. The `deps` paths are relative to the `build.outDir`. The return value should be a relative path to the `build.outDir`.
 
 ```js twoslash
 /** @type {import('vite').UserConfig} */

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

@@ -166,15 +166,9 @@ export function buildImportAnalysisPlugin(config: ResolvedConfig): Plugin {
   const isWorker = config.isWorker
   const insertPreload = !(ssr || !!config.build.lib || isWorker)
 
-  const resolveModulePreloadDependencies =
-    config.build.modulePreload && config.build.modulePreload.resolveDependencies
   const renderBuiltUrl = config.experimental.renderBuiltUrl
-  const customModulePreloadPaths = !!(
-    resolveModulePreloadDependencies || renderBuiltUrl
-  )
   const isRelativeBase = config.base === './' || config.base === ''
-  const optimizeModulePreloadRelativePaths =
-    isRelativeBase && !customModulePreloadPaths
+  const optimizeModulePreloadRelativePaths = isRelativeBase && !renderBuiltUrl
 
   const { modulePreload } = config.build
   const scriptRel =
@@ -189,10 +183,10 @@ export function buildImportAnalysisPlugin(config: ResolvedConfig): Plugin {
   // This is maintained to keep backwards compatibility as some users developed plugins
   // using regex over this list to workaround the fact that module preload wasn't
   // configurable.
-  const assetsURL = customModulePreloadPaths
-    ? // If `experimental.renderBuiltUrl` or `build.modulePreload.resolveDependencies` are used
-      // the dependencies are already resolved. To avoid the need for `new URL(dep, import.meta.url)`
-      // a helper `__vitePreloadRelativeDep` is used to resolve from relative paths which can be minimized.
+  const assetsURL = renderBuiltUrl
+    ? // If `experimental.renderBuiltUrl` is used, the dependencies are already resolved.
+      // To avoid the need for `new URL(dep, import.meta.url)`, a helper `__vitePreloadRelativeDep` is
+      // used to resolve from relative paths which can be minimized.
       `function(dep, importerUrl) { return dep[0] === '.' ? new URL(dep, importerUrl).href : dep }`
     : optimizeModulePreloadRelativePaths
       ? // If there isn't custom resolvers affecting the deps list, deps in the list are relative
@@ -353,7 +347,7 @@ export function buildImportAnalysisPlugin(config: ResolvedConfig): Plugin {
           str().appendRight(
             expEnd,
             `,${isModernFlag}?${preloadMarker}:void 0${
-              optimizeModulePreloadRelativePaths || customModulePreloadPaths
+              optimizeModulePreloadRelativePaths || renderBuiltUrl
                 ? ',import.meta.url'
                 : ''
             })`,
@@ -580,7 +574,7 @@ export function buildImportAnalysisPlugin(config: ResolvedConfig): Plugin {
 
               if (markerStartPos > 0) {
                 // the dep list includes the main chunk, so only need to reload when there are actual other deps.
-                const depsArray =
+                let depsArray =
                   deps.size > 1 ||
                   // main chunk is removed
                   (hasRemovedPureCssChunk && deps.size > 0)
@@ -591,33 +585,29 @@ export function buildImportAnalysisPlugin(config: ResolvedConfig): Plugin {
                       : [...deps]
                     : []
 
-                let renderedDeps: number[]
-                if (normalizedFile && customModulePreloadPaths) {
-                  const { modulePreload } = config.build
-                  const resolveDependencies = modulePreload
-                    ? modulePreload.resolveDependencies
-                    : undefined
-                  let resolvedDeps: string[]
-                  if (resolveDependencies) {
-                    // We can't let the user remove css deps as these aren't really preloads, they are just using
-                    // the same mechanism as module preloads for this chunk
-                    const cssDeps: string[] = []
-                    const otherDeps: string[] = []
-                    for (const dep of depsArray) {
-                      ;(dep.endsWith('.css') ? cssDeps : otherDeps).push(dep)
-                    }
-                    resolvedDeps = [
-                      ...resolveDependencies(normalizedFile, otherDeps, {
-                        hostId: file,
-                        hostType: 'js',
-                      }),
-                      ...cssDeps,
-                    ]
-                  } else {
-                    resolvedDeps = depsArray
+                const resolveDependencies = modulePreload
+                  ? modulePreload.resolveDependencies
+                  : undefined
+                if (resolveDependencies && normalizedFile) {
+                  // We can't let the user remove css deps as these aren't really preloads, they are just using
+                  // the same mechanism as module preloads for this chunk
+                  const cssDeps: string[] = []
+                  const otherDeps: string[] = []
+                  for (const dep of depsArray) {
+                    ;(dep.endsWith('.css') ? cssDeps : otherDeps).push(dep)
                   }
+                  depsArray = [
+                    ...resolveDependencies(normalizedFile, otherDeps, {
+                      hostId: file,
+                      hostType: 'js',
+                    }),
+                    ...cssDeps,
+                  ]
+                }
 
-                  renderedDeps = resolvedDeps.map((dep) => {
+                let renderedDeps: number[]
+                if (renderBuiltUrl) {
+                  renderedDeps = depsArray.map((dep) => {
                     const replacement = toOutputFilePathInJS(
                       dep,
                       'asset',