Improve error message / output when requesting multiple lags in covidcast::covidcast_signals

[brookslogan]

It appears that the query composer expects lag to be scalar, but covidcast_signals does not check this, and the error message when feeding in vector/multiple lags isn't immediately clear. (Although the docs for covidcast_signals do state that lag should be an "integer".)

library("pipeR")
library("tidyverse")
library("covidcast")

analysis.date = as.Date("2022-01-17")

signal.descriptions = tribble(
  ~data_source, ~signal, ~dual_lag,
  "jhu-csse", "confirmed_7dav_incidence_prop", 1L,
  "jhu-csse", "confirmed_7dav_incidence_prop", 8L,
  "fb-survey", "smoothed_hh_cmnty_cli", 1L,
  "fb-survey", "smoothed_hh_cmnty_cli", 8L,
  "doctor-visits", "smoothed_adj_cli", 1L,
  "doctor-visits", "smoothed_adj_cli", 8L,
  "quidel", "covid_ag_smoothed_pct_positive", 1L,
  "quidel", "covid_ag_smoothed_pct_positive", 8L,
  )

signal.dfs = covidcast_signals(
  data_source = signal.descriptions[["data_source"]],
  signal = signal.descriptions[["signal"]],
  lag = signal.descriptions[["dual_lag"]],
  geo_type = "state",
  as_of=analysis.date
) %>>%
  map2(function(signal.df, dual.lag) {
    signal.df %>>%
      mutate(time_value = time_value + dual.lag)
  })

Output:

Error in vapply(elements, encode, character(1)) : 
  values must be length 1,
 but FUN(X[[10]]) result is length 8

Investigation via "recover":

Enter a frame number, or 0 to exit   

 1: covidcast_signals(data_source = signal.descriptions[["data_source"]], signa
 2: covidcast_signals(data_source = signal.descriptions[["data_source"]], signa
 3: covidcast_signal(data_source = data_source[i], signal = signal[i], start_da
 4: covidcast_days(data_source, signal, start_day, end_day, geo_type, geo_value
 5: covidcast(data_source = data_source, signal = signal, time_type = time_type
 6: .request(params)
 7: httr::GET(getOption("covidcast.base_url", default = COVIDCAST_BASE_URL), ht
 8: handle_url(handle, url, ...)
 9: build_url(utils::modifyList(old, new))
10: compose_query(compact(url$query))
11: vapply(elements, encode, character(1))

Selection: Enter an item from the menu, or 0 to exit
Selection: 11
Called from: top level 
Browse[1]> ls()
[1] "FUN"       "FUN.VALUE" "i"         "USE.NAMES" "X"        
Browse[1]> X
$source
[1] "covidcast"

$data_source
[1] "jhu-csse"

$signal
[1] "confirmed_7dav_incidence_prop"

$time_type
[1] "day"

$geo_type
[1] "state"

$time_values
[1] "20200220, 20200221, 20200222, 20200223, 20200224, 20200225, 20200226, 20200227, 20200228, 20200229, 20200301, 20200302, 20200303, 20200304, 20200305, 20200306, 20200307, 20200308, 20200309, 20200310, 20200311, 20200312, 20200313, 20200314, 20200315, 20200316, 20200317, 20200318, 20200319, 20200320, 20200321, 20200322, 20200323, 20200324, 20200325, 20200326, 20200327, 20200328, 20200329, 20200330, 20200331, 20200401, 20200402, 20200403, 20200404, 20200405, 20200406, 20200407, 20200408, 20200409, 20200410, 20200411, 20200412, 20200413, 20200414, 20200415, 20200416, 20200417, 20200418, 20200419, 20200420, 20200421, 20200422, 20200423, 20200424"

$geo_value
[1] "*"

$format
[1] "csv"

$as_of
[1] "20220117"

$lag
[1] 1 8 1 8 1 8 1 8

Browse[1]>