fix(uploads): avoid making redundant memory copies (#1043)

Author: stainless-app[bot]

Diff for: src/uploads.ts

@@ -107,8 +107,10 @@ export async function toFile(
   // If it's a promise, resolve it.
   value = await value;
 
-  // Use the file's options if there isn't one provided
-  options ??= isFileLike(value) ? { lastModified: value.lastModified, type: value.type } : {};
+  // If we've been given a `File` we don't need to do anything
+  if (isFileLike(value)) {
+    return value;
+  }
 
   if (isResponseLike(value)) {
     const blob = await value.blob();
@@ -126,7 +128,7 @@ export async function toFile(
 
   name ||= getName(value) ?? 'unknown_file';
 
-  if (!options.type) {
+  if (!options?.type) {
     const type = (bits[0] as any)?.type;
     if (typeof type === 'string') {
       options = { ...options, type };

Diff for: tests/uploads.test.ts

@@ -54,4 +54,12 @@ describe('toFile', () => {
     const file = await toFile(input);
     expect(file.name).toEqual('uploads.test.ts');
   });
+
+  it('does not copy File objects', async () => {
+    const input = new File(['foo'], 'input.jsonl', { type: 'jsonl' });
+    const file = await toFile(input);
+    expect(file).toBe(input);
+    expect(file.name).toEqual('input.jsonl');
+    expect(file.type).toBe('jsonl');
+  });
 });