Can't upload file with `multipart/form-data` in Deno Deploy

[jcs224]

This app works fine with the Deno CLI, but not Deno Deploy:

https://dash.deno.com/playground/jcs224-zbar-wasm-oak

The multipart/form-data file upload doesn't work because it's trying to run Deno.makeTempDir and Deploy doesn't have the ability to write files.

The failing line is 27, const data = await body.value.read().

Is there a way to get the multipart file data without writing a temp dir? I was able to do this with the web-native FormData without Oak:

https://developer.mozilla.org/en-US/docs/Web/API/FormData/get

[jcs224]

Or, at least, is there a way to access the underlying Request object in Oak, within a route? I'm struggling to find it if there is...

[yubin-code]

Have you found a solution

[jcs224]

Actually, I have! Feels a little hack-y, but it works. It involves getting the raw request payload, and parsing it ourselves.

Here's a quick snippet, not a full example:

// Using a multiparser elsewhere in the community
import { multiParser } from 'https://deno.land/x/multiparser/mod.ts'
// ...
router
.post('/upload', async (ctx, next) => {
  const body = await ctx.request.body({
    type: 'form-data'
  })

  const form = await multiParser(ctx.request.originalRequest.request)

  const img = form.files['image-upload'].content
  // ...
})

Here's a complete example: https://dash.deno.com/playground/jcs224-oak-zbar-multipart

I still think this should be fixed within Oak, but this is a good enough workaround for now.

[linhub15]

The type form-data writes to file because the maxSize defaults to 0.

oak/multipart.ts

Lines 111 to 118 in 91b7aaa

	/** The maximum size (in bytes) of a file to hold in memory, and not write
	* to disk. This defaults to `0`, so that all multipart form files are
	* written to disk. When set to a positive integer, if the form data file is
	* smaller, it will be retained in memory and available in the `.content`
	* property of the `FormDataFile` object. If the file exceeds the `maxSize`
	* it will be written to disk and the `.filename` property will contain the
	* full path to the output file. */
	maxSize?: number;

Try setting a maxSize value to a number larger than the expected image size (in bytes).

const data = await body.value.read({ maxSize: 10_000_000 });