openapi-fetch Content-Length Issue Reproduction

This repository demonstrates an issue where openapi-fetch sends a Content-Length header that is twice as large as expected for file uploads, compared to using plain fetch.

Reproduction Steps

1. Clone the repository:

2. Install dependencies and run the project:

   pnpm install
   pnpm dev

3. Access the UI: Open your browser to http://localhost:5173 (or the port indicated by Vite).

4. Upload and test:

   • Select a file using the file input.
   • Open your backend console (where pnpm dev is running).
   • Click each of the three buttons:
     • "Upload with plain fetch"
     • "Upload with new Request"
     • "Upload with openapi-fetch"

5. Observe the Content-Length: In the backend console, you will observe the Content-Length header logged for each upload. The Content-Length for "Upload with plain fetch" will be approximately half the size of the Content-Length for "Upload with new Request" and "Upload with openapi-fetch". This highlights the unexpected larger Content-Length sent when new Request (used internally by openapi-fetch) is involved in file uploads.