Stringify with "arrayFormat: comma" encodes objects inside arrays as "[object Object]"

[FreekyMage]

Tested on version 6.9.4

Stringify with arrayFormat: comma encodes objects inside arrays as [object Object]

I took this code from the examples:

qs.stringify({ a: { b: { c: 'd', e: 'f' } } });
// 'a[b][c]=d&a[b][e]=f'

and added an array around the inside object

qs.stringify({ a: { b: [{ c: 'd', e: 'f' }] } }, { encode: false, arrayFormat: 'comma' })
// 'a[b]=[object Object]'

The inside data is lost this way.

I tried the allowDots setting too, but that didn't fix anything.

I'm not sure what the output should be like exactly, but this is unusable right now.
In my project I did Array.map(p => ${p.ID}::${p.Value}), but that's very specific and I'm unsure if the :: is a good seperator.

[ljharb]

I agree the current behavior is unusable. However, it is really unclear to me what the format should be, because the "comma" format doesn't work the same way normal query strings work. In other words, i have no idea whatsoever how an object inside an array would be represented in that format. Any suggestions?

cc @daggerjames @bryanlarsen who originally implemented/requested this format

[ls-urs-keller]

I guess arrayFormat: 'comma' should only be applied to an array with primitives e.g. number, string ...

[ljharb]

@ls-urs-keller one possibility is that qs could throw if it encounters a non-primitive when stringifying arrayFormat comma, but maybe there's something useful to be done instead.

[ls-urs-keller]

My need is compact query strings when possible, but still, have it work correctly for nested object arrays. I'm using this workaround for the moment:

const stringifyOpts = {
  allowDots: true,
  filter: (_prefix: string, value?: unknown): unknown => {
    const isNonNullPrimitive = (x?: unknown): boolean => !!x && Object(x) !== x;
    return Array.isArray(value) &&
      value.filter((v) => !isNonNullPrimitive(v) || v.indexOf(',') > -1).length === 0
      ? value.join(',')
      : value;
  },
};
stringify(queryParams, stringifyOpts)

[ljharb]

You're missing a few primitive types; i'd suggest doing Object(x) === x to determine if something's an object or not.

[ls-urs-keller]

You're missing a few primitive types; i'd suggest doing Object(x) === x to determine if something's an object or not.

Thank you. How about now?
Just wondering if this remark is valid here as well https://github.com/ljharb/qs/blob/main/lib/stringify.js#L51 ?

[nandi95]

@ls-urs-keller one possibility is that qs could throw if it encounters a non-primitive when stringifying arrayFormat comma, but maybe there's something useful to be done instead.

This is a good idea as people will likely get tripped up by this

[ls-urs-keller]

@ls-urs-keller one possibility is that qs could throw if it encounters a non-primitive when stringifying arrayFormat comma, but maybe there's something useful to be done instead.

This is a good idea as people will likely get tripped up by this

I would prefer a mixed mode as per my comments above.

[ljharb]

Howdy, folks that care about the comma array format!

My intuition is that what you want most is either to be able to round-trip things between parse and stringify (which requires [] brackets to be added on one-item arrays in stringify, or on all of them); or, to match the API of a specific server implementation.

If the latter, can folks please describe exactly what they're using and what format it requires? If it supports what qs calls brackets, indices, or repeat, please also explain why you need to use comma over those.

[runspired]

Most likely every user of JSON:API

https://jsonapi.org/format/#fetching-includes

The value of the include parameter MUST be a comma-separated (U+002C COMMA, “,”) list of relationship paths. A relationship path is a dot-separated (U+002E FULL-STOP, “.”) list of relationship names. An empty value indicates that no related resources should be returned.