Pass detailed error message along to user if possible (closes #7)

DESCRIPTION

@@ -19,7 +19,8 @@ Imports:
     crul (>= 0.5.2),
     jsonlite (>= 1.5),
     data.table,
-    tibble
+    tibble,
+    httpcode (>= 0.2.0)
 Suggests:
     testthat,
     vcr (>= 0.2.0.9114)

R/zzz.R

@@ -17,7 +17,7 @@ ma_HTTP <- function(path, args, key, method = "GET", body = list(),
     GET = cli$get(path, query = args, ...),
     POST = cli$post(path, query = args, body = body, encode = encode, ...)
   )
-  res$raise_for_status()
+  raise_for_status2(res)
   txt <- res$parse("UTF-8")
   jsonlite::fromJSON(txt, flatten = TRUE)
 }
@@ -49,3 +49,31 @@ assert <- function(x, y) {
     }
   }
 }
+
+raise_for_status2 <- function(res) {
+  if (res$status_code >= 300) {
+    er_lst <- tryCatch(
+      parse_error_msg(res),
+      error = function(e) httpcode::http_code(res$status_code)
+    )
+    er_msg <- sprintf(
+      "%s (HTTP %s)\nExplanation: %s",
+      res$status_code, er_lst$message, er_lst$explanation
+    )
+    stop(er_msg, call. = FALSE)
+  }
+}
+
+parse_error_msg <- function(res) {
+  txt <- res$parse("UTF-8")
+  er_vec <- unlist(jsonlite::fromJSON(txt))
+  # er_vec names used to be capitilized (e.g., "Error.Code", not "error.code").
+  # convert to lowercase just in case API goes back to using caps.
+  names(er_vec) <- tolower(names(er_vec))
+  list(
+    # the error.code element refers to a short error message, not the HTTP
+    # status code
+    message = er_vec[["error.code"]],
+    explanation = er_vec[["error.message"]]
+  )
+}

tests/fixtures/ma_error.yml

@@ -0,0 +1,30 @@
+http_interactions:
+- request:
+    method: get
+    uri: https://api.labs.cognitive.microsoft.com/academic/v1.0/evaluate?expr=hi-there&count=10&offset=0&attributes=Id%2CAA.AuN%2CJ.JN%2CTi%2CY%2CE%2CCC&model=latest
+    body:
+      encoding: ''
+      string: ''
+    headers:
+      User-Agent: libcurl/7.54.0 r-curl/3.2 crul/0.6.0
+      Accept-Encoding: gzip, deflate
+      Accept: application/json, text/xml, application/xml, */*
+      Ocp-Apim-Subscription-Key: <<<microdemic_api_key>>>
+  response:
+    status:
+      status_code: '400'
+      message: Bad Request
+      explanation: Bad request syntax or unsupported method
+    headers:
+      status: HTTP/1.1 400 Bad Request
+      content-length: '100'
+      content-type: application/json
+      access-control-allow-origin: '*'
+      request-context: appId=cid-v1:7cd06f0e-6d73-46a5-9c10-4ebe681d0156
+      x-powered-by: ASP.NET
+      date: Sat, 12 Jan 2019 03:18:16 GMT
+    body:
+      encoding: ASCII-8BIT
+      string: eyJFcnJvciI6eyJDb2RlIjoiQmFkIEFyZ3VtZW50IiwiTWVzc2FnZSI6IkludmFsaWQgcXVlcnkgZXhwcmVzc2lvblxyXG5QYXJhbWV0ZXIgbmFtZTogZXhwcmVzc2lvbiJ9fQ==
+  recorded_at: 2019-01-12 03:18:16 GMT
+  recorded_with: vcr/0.1.0, webmockr/0.2.6, crul/0.6.0

tests/testthat/test-error-msgs.R

@@ -0,0 +1,12 @@
+context("ma_error")
+
+test_that("Detailed error messages are provided when possible", {
+  skip_on_cran()
+
+  vcr::use_cassette("ma_error", {
+    expect_error(
+      ma_search(query = "hi-there"),
+      "query"
+    )
+  }, preserve_exact_body_bytes = TRUE)
+})