fix: handle commas in static file paths (#3770)

After #3659, static file handling correctly supports spaces and encoded
paths, but filenames containing commas are not resolved.

Example:
- File: `foo,bar.css`
- Stored in cache as: `/foo%2Cbar.css`
- Request: `/foo,bar.css`

---------

Co-authored-by: Bartek Iwańczuk <biwanczuk@gmail.com>

Author: SebF33

packages/fresh/src/middlewares/static_files.ts

@@ -4,6 +4,14 @@ import { BUILD_ID } from "@fresh/build-id";
 import { tracer } from "../otel.ts";
 import { getBuildCache } from "../context.ts";
 
+/** Decode and re-encode each path segment so that characters like commas
+ *  are percent-encoded consistently with how `prepareStaticFile` stores
+ *  entries in the build cache. */
+function normalizePathname(pathname: string): string {
+  return "/" +
+    pathname.split("/").filter(Boolean).map(encodeURIComponent).join("/");
+}
+
 /**
  * Fresh middleware to serve static files from the `static/` directory.
  * ```ts
@@ -25,6 +33,13 @@ export function staticFiles<T>(): Middleware<T> {
         : "/";
     }
 
+    try {
+      pathname = normalizePathname(decodeURIComponent(pathname));
+    } catch (_e: unknown) {
+      if (!(_e instanceof URIError)) throw _e;
+      return await ctx.next();
+    }
+
     // Fast path bail out
     const startTime = performance.now() + performance.timeOrigin;
     const file = await buildCache.readFile(pathname);

packages/fresh/src/middlewares/static_files_test.ts

@@ -296,3 +296,29 @@ Deno.test("static files - fallthrough", async () => {
   expect(text).toEqual("it works");
   expect(called).toEqual(["before", "after"]);
 });
+
+Deno.test("static files - comma in pathname", async () => {
+  const key = systemPathToUrlEncoded("foo,bar.css");
+
+  const buildCache = new MockBuildCache({
+    [key]: {
+      content: "body {}",
+      hash: null,
+    },
+  });
+
+  const server = serveMiddleware(
+    staticFiles(),
+    { buildCache },
+  );
+
+  // Browser/request path usually keeps the comma unencoded
+  let res = await server.get("/foo,bar.css");
+  await res.body?.cancel();
+  expect(res.status).toEqual(200);
+
+  // Encoded form should also resolve
+  res = await server.get("/foo%2Cbar.css");
+  await res.body?.cancel();
+  expect(res.status).toEqual(200);
+});