Detect file streams by looking at URL path prefix

The file streaming API is hosted at
https://stream.replicate.com/v1/files so we can use this prefix to
determine that the response will contain file entities. This is far
cleaner than relying on the event contents.

Author: aron

lib/stream.js

@@ -53,6 +53,7 @@ class ServerSentEvent {
  */
 function createReadableStream({ url, fetch, options = {} }) {
   const { useFileOutput = true, headers = {}, ...initOptions } = options;
+  const shouldProcessFileOutput = useFileOutput && isFileStream(url);
 
   return new ReadableStream({
     async start(controller) {
@@ -89,9 +90,9 @@ function createReadableStream({ url, fetch, options = {} }) {
 
         let data = event.data;
         if (
-          useFileOutput &&
-          typeof data === "string" &&
-          (data.startsWith("https:") || data.startsWith("data:"))
+          event.event === "output" &&
+          shouldProcessFileOutput &&
+          typeof data === "string"
         ) {
           data = createFileOutput({ url: data, fetch });
         }
@@ -169,6 +170,13 @@ function createFileOutput({ url, fetch }) {
   });
 }
 
+function isFileStream(url) {
+  try {
+    return new URL(url).pathname.startsWith("/v1/files/");
+  } catch {}
+  return false;
+}
+
 module.exports = {
   createFileOutput,
   createReadableStream,