part.set_content_disposition is ignored

[MattIPv4]

Long story short

Using part.set_content_disposition for some multipart file stuff, couldn't get it to work.
So I checked the part header, which is as I expected and then made a fake writer to check what the payload being sent actually was. The content disposition in the payload doesn't at all match what I have set in the part.

Expected behaviour

The content disposition in the payload is as set in the part.

Actual behaviour

It appears to generate a fresh content disposition.

Steps to reproduce

class Writer:

    def __init__(self):
        self.buffer = ""

    async def write(self, stuff):
        self.buffer += stuff.decode('utf-8','ignore')

    def done(self):
        print(self.buffer[:300])

# Generate multipart
with aiohttp.MultipartWriter('form-data') as mp:
    part = mp.append(open(path, 'rb'))
    part.set_content_disposition(
        'form-data',
        quote_fields=False,
        name='files[]',
        filename=os.path.split(path)[1]
    )
    # Fix aiohttp being retarded
    part._headers['Content-Disposition'] = part._headers['Content-Disposition'].split(" filename*=utf-8", 1)[0]
    print("\n", part._headers['Content-Disposition'], "\n")
    w = Writer()
    await mp.write(w)
    w.done()

Your environment

Aiohttp 3.2.1
Python 3.6
macOS 10.13.4

The issue (as far as I can tell)

https://github.com/aio-libs/aiohttp/blob/master/aiohttp/multipart.py#L754-L755
It appears there that the payload headers are saved separately and so no matter what you do to the returned part after it's appended, the headers will never actually be updated in the multipart.

Hotfix (until this issue is resolved)

Create your payload yourself, set headers etc. before you append to the multipart.
eg.

# Hotfix
from multidict import CIMultiDict
payload = aiohttp.payload.get_payload(open(path, 'rb'), headers=CIMultiDict())
payload.set_content_disposition(
    'form-data',
    quote_fields=False,
    name='files[]',
    filename=os.path.split(path)[1]
)
payload._headers['Content-Disposition'] = payload._headers['Content-Disposition'].split(" filename*=utf-8", 1)[0]

# Add part to multipart
part = mp.append(payload)

[asvetlov]

@kxepal ?
You remember this code better than me.

[SphericalNumerics]

Any updates on the status of this bug? The hotfix given above doesn't seem to work for me---the content-disposition header is still blank.

[asvetlov]

No progress yet.
Pull Request is welcome!

[elsampsa]

I stumbled to this same bug today .. please fix

[kxepal]

Will do this today. I seems like sort of mistake happended after payloads introduction where payload headers in MultipartWriter.parts lives own life separated from Payload.headers.

[elsampsa]

Thanks!

I started to look at this myself but its a bit intractable at first sight .. I was looking at when Payload.set_content_type gets called (printing logs) .. and it seems to work fine. But in the end, something else (what?) overwrites Content-Disposition

EDIT

When doing like this:

mpwriter = aiohttp.MultipartWriter('form-data')
...
subwriter = mpwriter.append(f)
...
subwriter.set_content_disposition('attachments', filename='5c2ca3d448cf7d16922acfdc.jpg')

The problem seems to be that when MultipartWriter.append is called, that's the only time when the headers are constructed (this takes place in MultipartWriter.append_payload)

Using set_content_disposition after that has no effect : the headers don't get updated

[lock]

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