Fix Query Params Parsing

[coldlink]

What does this change?

In #2875 we fixed an issue where there were duplicate query params appearing in the URL.

This only fixes this issue from the client side, the server side issue still remains if duplicate query params were to be provided.

Essentially express query parameter parsing will convert a value of a query parameter into an array if it sees multiple keys for that parameter.

e.g.

?foo=bar&foo=baz&hello=world

would get parsed into

{
 foo: ['bar', 'baz'],
 hello: 'world'
}

In Gateway we don’t use duplicate query parameters and they should never exist.

By default, express will use https://www.npmjs.com/package/qs to parse query params, which is more powerful than what we need (called 'extended' in the express docs, see https://expressjs.com/en/api.html#app.settings.table).

Even the "simple" mode in express uses node's querystring api doesn't work. This will also parse duplicate query params into an array, which is not what we want, as shown by the example: https://nodejs.org/api/querystring.html#querystringparsestr-sep-eq-options

However, we can use a custom query parser to use the native URLSearchParams API, which will parse duplicate query params into the last value, which is exactly what we want.

So that ?foo=bar&foo=baz&hello=world => { foo: 'baz', hello: 'world' }.

This can be tested in a node repl or browser console by running:

Object.fromEntries(new URLSearchParams(`foo=bar&foo=baz&hello=world`).entries())

which returns the expected result.

Tested

• DEV
  • inc. node repl
• CODE

[github-actions]

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From guardian/actions-riff-raff.

[akinsola-guardian]

LGTM