Stringifying using different arrayFormats, then parsed, create different things

It seems stringifying my metadata object with arrayFormat: brackets, then parsing it, creates a different object to stringifying with arrayFormat: indices then parsing that string.

> const qs = require('qs');

> metadata = [{key: "a", value: "2"}, {key: "b", value: "3"}]
[ { key: 'a', value: '2' }, { key: 'b', value: '3' } ]

> brackets = qs.stringify({"metadata": metadata}, { arrayFormat: "brackets"})
'metadata%5B%5D%5Bkey%5D=a&metadata%5B%5D%5Bvalue%5D=2&metadata%5B%5D%5Bkey%5D=b&metadata%5B%5D%5Bvalue%5D=3'

> parsed_brackets = qs.parse(brackets)
{ metadata: [ { key: [Array], value: [Array] } ] }

> parsed_brackets["metadata"]
[ { key: [ 'a', 'b' ], value: [ '2', '3' ] } ]

> indices = qs.stringify({"metadata": metadata}, { arrayFormat: "indices"})
'metadata%5B0%5D%5Bkey%5D=a&metadata%5B0%5D%5Bvalue%5D=2&metadata%5B1%5D%5Bkey%5D=b&metadata%5B1%5D%5Bvalue%5D=3'

> parsed_indices = qs.parse(indices)
{ metadata: [ { key: 'a', value: '2' }, { key: 'b', value: '3' } ] }

Am I doing something wrong? Is this expected? Is this just an issue with stringifying/parsing nested objects?

[ljharb]

@nigeldunne in this case, %2c isn’t a comma to be used for splitting. if you parse foo=a,b it will split properly.

I’d say the issue is that stringify needs to produce an unescaped comma when arrayFormat is “comma”.

[nigeldunne]

@ljharb The “round trip” still does not work when arrayFormat is “comma”:

qs.stringify({ foo: [ ‘a’, ‘b’ ] }, { arrayFormat: ‘comma’ }) ‘foo=a%2Cb’ qs.parse(‘foo=a%2Cb’, { comma: true }) { foo: ‘a,b’ } //expecting { foo: [ ‘a’, ‘b’ ]