无法将附件正确上传到 Azure DevOps API（0kb 结果）

Question

I'm trying to upload attachments to work items in Azure DevOps using the REST API. However, while I can get the attachment "uploaded" and attached to the work item, the attachment is always 0KB in size, both in the UI and when I download it.

The API looks fairly straightforward, and I've not had issues with the dozen other APIs I've used. I just can't figure out where this is going wrong. Here's the code I'm using for this:

import os
import sys
import requests


_credentials = ("user@example.com", "password")

def post_file(url, file_path, file_name):

    file_size = os.path.getsize(file_path)

    headers = {
        "Accept": "application/json",
        "Content-Size": str(file_size),
        "Content-Type": "application/octet-stream",
    }

    request = requests.Request('POST', url, headers=headers, auth=_credentials)
    prepped = request.prepare()

    with open(file_path, 'rb') as file_handle:
        prepped.body = file_handle.read(file_size)

    return requests.Session().send(prepped)


def add_attachment(path_to_attachment, ticket_identifier):
    filename = os.path.basename(path_to_attachment)

    response = post_file(
        f"https://[instance].visualstudio.com/[project]/_apis/wit/attachments?uploadType=Simple&fileName={filename}&api-version=1.0",
        path_to_attachment,
        filename
    )

    data = response.json()
    attachment_url = data["url"]

    patch_result = requests.patch(
        f"https://[instance].visualstudio.com/[project]/_apis/wit/workitems/{ticket_identifier}?api-version=4.1",
        auth=_credentials, 
        headers={
            "Accept": "application/json",
            "Content-Type": "application/json-patch+json",
        }, 
        json=[
            {
                "op": "add",
                "path": "/relations/-",
                "value": {
                    "rel": "AttachedFile",
                    "url": attachment_url
                },
            }
        ]
    )

    print(patch_result)
    print(patch_result.text)

add_attachment(sys.argv[1], sys.argv[2])

I've tried setting/removing/varying every possible header value I can think of. I've tried using the files attribute that's on the post method in requests (but dropped it because it set Content-Disposition, but all examples I've seen don't use that), I've tried setting the area path parameter, I've tried everything I can think of, but nothing has made any difference.

I've even used Fiddler to watch how the actual site does it, then copied the headers to a new request in Python and sent that and I'm still seeing the 0kb result.

I'm pretty much out of ideas at this point, so if anyone knows where I may be going wrong, it would be much appreciated!

Answer 1

The answer to this wasn't obvious. It was the second call to link the attachment to the work item that had the bug. If a comment isn't specified, it doesn't link correctly. ie This code:

json=[
    {
        "op": "add",
        "path": "/relations/-",
        "value": {
            "rel": "AttachedFile",
            "url": attachment_url
        },
    }
]

Should have been:

json=[
    {
        "op": "add",
        "path": "/relations/-",
        "value": {
            "rel": "AttachedFile",
            "url": attachment_url,
            "attributes": {
                "comment": ""
            }
        },
    }
]

This isn't documented, nor is it expected that you'd get a 0KB attachment upload if you don't specify a comment in the linking phase. No other link types need a comment. I'm going to raise this issue with the documentation maintainers.

Answer 2

I've been working on this as well and found a solution. You have to add the filesize parameter in the json. You don't have to put a comment to get size to show.

Note it appears that DevOps rounds to the nearest 1,000 (my test file was 325 and it shows as 1K in DevOps)

    file_size = os.path.getsize(file_path)

    json = [
        {
            "op": "add",
            "path": "/relations/-",
            "value": {"rel": "AttachedFile", "url": attachment.url,
                "attributes": {"comment": "DevOps Test", "resourceSize": file_size},
             }
        }
    ]

Hope this helps someone!

Answer 3

Your post file function should become:

def post_file(url, file_path, file_name):
    file_size = os.path.getsize(file_path)

    headers = {
        "Accept": "application/json",
        "Content-Size": str(file_size),
        "Content-Type": "application/octet-stream",
    }
    files = {'file': open(file_path, 'rb')}
    r = requests.post(url, files=files, headers=headers, auth=(username, token))
    return r