向OpenAI API上传Rust文件遇415错误，寻求解决方法

我想开发一个工具让ChatGPT为Rust文件生成文档，但OpenAI API消息长度有限，打算通过上传文件提供上下文。用reqwest写的上传代码返回「Failed to upload file. Status code: 415 Unsupported Media Type」错误，改Content-Type为text/plain也没用，代码如下：

use std::fmt::Write;
use std::fs;
use std::io;
use std::io::Read;

use chatgpt::prelude::*;
use clap::Parser;
use syn;
use syn::Item;
use reqwest;

#[derive(Parser, Debug)]
#[command(author, version, about, long_about = None)]
struct Args
{
    /// Path to the source code to document
    #[arg(short, long)]
    file_path: String,
}

fn main()
{
    let args = Args::parse();

    let mut file = std::fs::File::open(args.file_path).unwrap();
    let mut content = String::new();
    file.read_to_string(&mut content).unwrap();

    let ast = syn::parse_file(&content).unwrap();
    let mut input_buffer = String::new();

    // Getting the API key here
    let key = "My key that I have replaced for obvious reasons";

    {
        // Create a reqwest client
        let client = reqwest::blocking::Client::new();

        // Make a POST request to the OpenAI API
        let response = client
            .post("https://api.openai.com/v1/files")
            .header("Authorization", "Bearer My key that I have replaced for obvious reasons")
            .header("Content-Type", "application/json")
            .body(content.clone())
            .send().unwrap();

        // Check if the request was successful
        if response.status().is_success() {
            println!("File uploaded successfully!");
        } else {
            println!("Failed to upload file. Status code: {}", response.status());
        }

        std::mem::forget(client);
        std::mem::forget(response);
    }
}

错误原因及修正方案 #

核心问题 #

OpenAI的/v1/files接口要求用multipart/form-data格式提交请求，而非直接传递文本内容或JSON。该接口必须包含两个字段：

• file：要上传的文件（需包含文件名和内容）
• purpose：文件用途，比如"assistants"（用于助手上下文）或"fine-tune"（用于微调）

代码修正步骤 #

1. 移除手动设置的Content-Type header，reqwest会自动为multipart请求生成正确的Content-Type
2. 使用reqwest::blocking::multipart::Form构建请求体，添加file和purpose字段
3. 无需调用std::mem::forget，reqwest的Client和Response会自动处理内存释放

修正后的代码 #

use std::fs;
use clap::Parser;
use reqwest::blocking::multipart;

#[derive(Parser, Debug)]
#[command(author, version, about, long_about = None)]
struct Args
{
    /// Path to the source code to document
    #[arg(short, long)]
    file_path: String,
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let args = Args::parse();
    let api_key = "Your actual OpenAI API key here";

    // 读取文件内容
    let file_content = fs::read_to_string(&args.file_path)?;
    // 构建multipart表单
    let form = multipart::Form::new()
        // 添加文件字段：文件名从路径获取，内容为读取的文本
        .file("file", &args.file_path)?
        // 设置文件用途，这里用assistants作为示例
        .text("purpose", "assistants");

    let client = reqwest::blocking::Client::new();
    let response = client
        .post("https://api.openai.com/v1/files")
        .header("Authorization", format!("Bearer {}", api_key))
        .multipart(form)
        .send()?;

    if response.status().is_success() {
        let response_json = response.json::<serde_json::Value>()?;
        println!("文件上传成功！文件ID: {}", response_json["id"]);
    } else {
        let error_msg = response.text()?;
        eprintln!("文件上传失败，状态码: {}，错误信息: {}", response.status(), error_msg);
    }

    Ok(())
}

额外说明 #

• 需要在Cargo.toml中添加serde_json依赖（用于解析响应）
• 确保API密钥正确，且账户有足够权限上传文件
• 文件大小不能超过OpenAI的限制（当前最大为512MB）

内容的提问来源于stack exchange，提问作者Makogan