Appending a Blob to FormData fails when filename not included in append()

To start with, thanks to all the maintainers for the amazing job on this lib!

Cannot read property 'replace' of undefined
TypeError: Cannot read property 'replace' of undefined
    at new File (/Users/alevine/planner-ui/node_modules/jsdom/lib/jsdom/living/file.js:14:40)
    at FormData.append (/Users/alevine/planner-ui/node_modules/jsdom/lib/jsdom/living/form-data.js:30:17)

Quick summary of what is happening:

1. Code creates new FormData in jsdom
2. .append() is called with 2 arguments (name and value), where value is a Blob created with new Blob()
3. jsdom calls new File(), using value.name as the filename
4. The constructor for File tries to call String.prototype.replace on fileName, which throws because fileName (which is optional for a manually constructed Blob) is undefined

I was able to address this in my own code for the time being by supplying the 3rd argument (filename) to append().

Here is some quick sample code that can be used to replicate:

var formData = new FormData();
var file = new Blob([
   JSON.stringify({})
], { type: 'application/json' });
formData.append('somename', file);

I’d be willing to contribute a fix, but I’m not 100% on what the correct fix is. I can try and dig into the spec once I’m outside of work hours, but any hints to send me in the right direction would be appreciated 😃

[domenic]

Thanks! Filed https://github.com/whatwg/xhr/issues/73; when we get some spec clarity here we can fix jsdom.

[DrewML]

You beat me to it - thank you!