Prioritize credentials_byo_oauth2()

NEWS.md

@@ -50,6 +50,11 @@ actually want to suppress auth with the default service account and auth as a
 normal user instead.
 This is especially likely to come up with gmailr / the Gmail API.
 
+* The credential-fetcher `credentials_byo_oauth2()` has been moved to the very
+  beginning of the default registry. The logic is that a user who has specified
+  a non-`NULL` value of `token` must mean business and does not want automagic
+  auth methods like ADC or GCE to be tried before using their `token` (#187).
+
 * The `...` in `cred_funs_all()` are now
   [dynamic dots](https://rlang.r-lib.org/reference/dyn-dots.html).
 

R/credential-function-registry.R

@@ -111,11 +111,11 @@ cred_funs_clear <- function() {
 cred_funs_set_default <- function() {
   cred_funs_clear()
   l <- list(
+    credentials_byo_oauth2       = credentials_byo_oauth2,
     credentials_service_account  = credentials_service_account,
     credentials_external_account = credentials_external_account,
     credentials_app_default      = credentials_app_default,
     credentials_gce              = credentials_gce,
-    credentials_byo_oauth2       = credentials_byo_oauth2,
     credentials_user_oauth2      = credentials_user_oauth2
   )
   cred_funs_set(l)