How to implement a modified "explode" option for .multi in req_url_query()?

[Aariq]

I'm working with the usa-npn API which takes multiple values for a query like so: x[1]=1&x[2]=2&x[3]=3. The .multi argument doesn't seem to be able to handle this and I have to construct the list of queries outside of req_url_query(). It seems like there isn't a way for a function supplied to .multi to use the parameter name. E.g., this doesn't work:

library(httr2)

#this sort of thing would be nice
foo <- function(x) {
  x_name <- deparse(substitute(x))
  glue::glue("{x_name}[{seq_along(x)}]={x}") %>% 
    glue::glue_collapse(sep = "&")
}
ID <- 5:7
foo(ID)
#> ID[1]=5&ID[2]=6&ID[3]=7

#but doesn't work here
request("https://example.com") %>% 
  req_url_query(
    ID = 5:7,
    .multi = foo
  )
#> <httr2_request>
#> GET https://example.com?ID=X[[i]][1]=5&X[[i]][2]=6&X[[i]][3]=7
#> Body: empty

^{Created on 2024-12-09 with reprex v2.1.1}

Is there a workaround for this? I looked at the code to figure out what "explode" does, and it seems like it behaves differently from an anonymous function—I couldn't figure it out.

[hadley]

There's no way to do it currently with .multi because it assumes that the names stay the same. You could however do something like this:

library(httr2)

foo <- function(nm, vals) {
  setNames(vals, paste0(nm, "[", seq_along(vals), "]"))
}
request("https://example.com") |>
  req_url_query(!!!foo("ID", 5:7))

[Aariq]

Thanks! That is a much "cleaner" solution than I had before

[hadley]

BTW does it still work with your API if you omit the index? i.e. x[]=1&x[]=2&x[]=3. If so you could do:

request("https://example.com") %>% 
  req_url_query(
    `ID[]` = 5:7,
    .multi = "explode"
  )

[Aariq]

BTW does it still work with your API if you omit the index? i.e. x[]=1&x[]=2&x[]=3. If so you could do:

request("https://example.com") %>% 
  req_url_query(
    `ID[]` = 5:7,
    .multi = "explode"
  )

I have no idea why, but that does work (at least for the endpoint I tested). Thanks for the suggestion!