fix(serve-static): serve precompressed files for application/octet-stream

[yusukebe]

Fixes #360

serveStatic({ precompressed: true }) didn't serve precompressed variants for application/octet-stream files like .bin, even when a .br/.zst/.gz existed. Now it does.

[yusukebe]

Hey @usualoma

I created this PR to fix #360. I thought it was better to handle application/octet-stream rather than update the docs as #360 said. Can you review?

[usualoma]

Hi @yusukebe,
Thank you.

By the way, is the reason you didn't embed it directly into COMPRESSIBLE_CONTENT_TYPE_REGEX here to avoid discrepancies with the COMPRESSIBLE_CONTENT_TYPE_REGEX in the Hono core?
https://github.com/honojs/hono/blob/b20d4225c9aa9e615717ca74e437852cc9fd5b94/src/utils/compress.ts#L9-L10

I understand the desire to distinguish this from the COMPRESSIBLE_CONTENT_TYPE_REGEX in the Hono core, since it’s also used by the “compress” middleware.

---

However, I think there’s also the view that, in the case of precompressed, the COMPRESSIBLE_CONTENT_TYPE_REGEX check isn’t necessary.

I feel it might also be a good idea to allow passing

diff --git i/src/serve-static.ts w/src/serve-static.ts
index 9daa4c8..bea3535 100644
--- i/src/serve-static.ts
+++ w/src/serve-static.ts
@@ -12,7 +12,7 @@ export type ServeStaticOptions<E extends Env = Env> = {
   root?: string
   path?: string
   index?: string // default is 'index.html'
-  precompressed?: boolean
+  precompressed?: boolean | ((options: { path: string; mimeType?: string }) => boolean)
   rewriteRequestPath?: (path: string, c: Context<E>) => string
   onFound?: (path: string, c: Context<E>) => void | Promise<void>
   onNotFound?: (path: string, c: Context<E>) => void | Promise<void>
@@ -65,6 +65,12 @@ export const serveStatic = <E extends Env = any>(
     console.error(`serveStatic: root path '${root}' is not found, are you sure it's correct?`)
   }
 
+  const precompressedFilter: (options: { path: string; mimeType?: string }) => boolean =
+    typeof options.precompressed === 'function'
+      ? options.precompressed
+      : ({ mimeType }) =>
+          options.precompressed && (!mimeType || COMPRESSIBLE_CONTENT_TYPE_REGEX.test(mimeType))
+
   return async (c, next) => {
     // Do nothing if Response is already set
     if (c.finalized) {
@@ -108,7 +114,7 @@ export const serveStatic = <E extends Env = any>(
     const mimeType = getMimeType(path)
     c.header('Content-Type', mimeType || 'application/octet-stream')
 
-    if (options.precompressed && (!mimeType || COMPRESSIBLE_CONTENT_TYPE_REGEX.test(mimeType))) {
+    if (precompressedFilter({ path, mimeType })) {
       const acceptEncodingSet = new Set(
         c.req
           .header('Accept-Encoding')

---

I thought about something like that, but I think it’s perfectly fine to target application/octet-stream for now!