If a response header has "content-type" = "", content() gives an error

[potterzot]

Reproducible example:

library(httr)
#fabricated response from USDA NASS QuickStats API
r <- list(
  url = "https://quickstats.nass.usda.gov/api/api_GET?key=<key removed>&sector_desc=ECONOMICS&commodity_desc=RENT&prodn_practice_desc=IRRIGATED&class_desc=CROPLAND&agg_level_desc=COUNTY&year__GE=1997&format=JSON",
  date = as.POSIXct("2017-12-20 22:43:47 GMT"),
  headers = list('content-type' = ""),
  content = charToRaw('{\"error\":[\"bad request - invalid query\"]}'))

class(r) <- "response"
class(r$headers) <- "insensitive"

#Call to httr::content without specifying type
content(r, as="text")

> Error in if (length(m) == 1 && m == -1) { : 
  missing value where TRUE/FALSE needed

#Works if specify type
content(r, as="text", type="text/json")
> '{\"error\":[\"bad request - invalid query\"]}'

This seems to be in the parse_media() function in media-parse.r, which works fine if type is NULL but not if type is "". type gets set to "" in the content() function if it is "" in the header.

[hadley]

library(httr)

r <- list(
  url = "https://quickstats.nass.usda.gov/api/api_GET?key=<key removed>&sector_desc=ECONOMICS&commodity_desc=RENT&prodn_practice_desc=IRRIGATED&class_desc=CROPLAND&agg_level_desc=COUNTY&year__GE=1997&format=JSON",
  date = as.POSIXct("2017-12-20 22:43:47 GMT"),
  headers = list('content-type' = ""),
  content = charToRaw('{\"error\":[\"bad request - invalid query\"]}')
)

class(r) <- "response"
class(r$headers) <- "insensitive"

content(r, as="text")
#> Error in if (length(m) == 1 && m == -1) {: missing value where TRUE/FALSE needed

^{Created on 2018-11-22 by the reprex package (v0.2.1)}