feat: add resolveBuiltUrl hook

For rewriting the public URLs of static assets.

packages/vite/src/node/plugin.ts

@@ -114,6 +114,16 @@ export interface Plugin extends RollupPlugin {
     ctx: HmrContext
   ): Array<ModuleNode> | void | Promise<Array<ModuleNode> | void>
 
+  /**
+   * Resolve an asset's public URL. This hook can call `this.emitFile` and
+   * return `__VITE_ASSET__${emitFileResult}__` to be replaced by Vite
+   * later in the build.
+   */
+  resolveBuiltUrl?(
+    this: PluginContext,
+    url: string
+  ): Promise<string | null | undefined> | string | null | undefined
+
   /**
    * extend hooks with ssr flag
    */

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

@@ -128,15 +128,16 @@ export function checkPublicFile(
   }
 }
 
-export function fileToUrl(
+export async function fileToUrl(
   id: string,
   config: ResolvedConfig,
   ctx: PluginContext
-): string | Promise<string> {
+): Promise<string> {
   if (config.command === 'serve') {
     return fileToDevUrl(id, config)
   } else {
-    return fileToBuiltUrl(id, config, ctx)
+    const builtUrl = await resolveBuiltUrl(id, config, ctx)
+    return builtUrl || fileToBuiltUrl(id, config, ctx)
   }
 }
 
@@ -252,19 +253,41 @@ export async function urlToBuiltUrl(
   url: string,
   importer: string,
   config: ResolvedConfig,
-  pluginContext: PluginContext
+  ctx: PluginContext
 ): Promise<string> {
+  const builtUrl = await resolveBuiltUrl(url, config, ctx)
+  if (builtUrl) {
+    return builtUrl
+  }
+
   if (checkPublicFile(url, config)) {
     return config.base + url.slice(1)
   }
+
   const file = url.startsWith('/')
     ? path.join(config.root, url)
     : path.join(path.dirname(importer), url)
+
   return fileToBuiltUrl(
     file,
     config,
-    pluginContext,
+    ctx,
     // skip public check since we just did it above
     true
   )
 }
+
+async function resolveBuiltUrl(
+  url: string,
+  config: ResolvedConfig,
+  ctx: PluginContext
+) {
+  for (const { resolveBuiltUrl } of config.plugins) {
+    if (resolveBuiltUrl) {
+      const result = await resolveBuiltUrl.call(ctx, url)
+      if (result) {
+        return result
+      }
+    }
+  }
+}