Add support for comma separated query parameters

[tylerlittlefield]

Consider this plumber.R file:

library(plumber)

#* Sort letters
#* @param letters:[]
#* @json
#* @get /letters
function(letters) {
  sort(letters)
}

How do I change the request from this:

http://127.0.0.1:9203/letters?letters=a&letters=b

To this:

http://127.0.0.1:9203/letters?letters=a,b

Swagger docs on parameter serialization: https://swagger.io/docs/specification/serialization/

[slodge]

This currently works for path variables:

#* Sort letters
#* @param letters:[string]
#* @json
#* @get /letters/<letters:[string]>
function(letters) {
  sort(letters)
}

(Also adding a note to self for the spec changes in PR #889)

[slodge]

Docs on path variables are in https://www.rplumber.io/articles/routing-and-input.html

[meztez]

Ref : https://community.rstudio.com/t/comma-separated-query-parameters-in-plumber-api/156781/2

[meztez]

Note : Think about issue with number conversion. Comma in values? I remember we played with the idea but decided against it because it created more problems? There might be a smart way to do it that will appear with automated argument conversion.

[thomasp85]

We could add some flexibility to the queryStringFilter() so that the defaults are kept but the user could opt in to non-exploded form. Happy to provide a PR if this is of interest

[schloerke]

Feels like if the parameter is documented as an array, we should try to allow for it. I believe the auto splitting of values is fair to achieve as that's most likely what the user wants. If the comma is NOT suppose to turn the value into an array, it can be sent as %2C (ex: letters=1%2C2 which resolves to letters = "1,2")

@thomasp85 can you make a PR? Thank you!