Introduce reprex.current_venue option

cc @kevinushey

Relates to #313

NEWS.md

@@ -36,6 +36,8 @@
 
 * Experimental venue "rtf" now works on Windows, to approximately the same extent as it works on macOS. In both cases, it still requires a working installation of the highlight command line tool (#331).
 
+* `reprex.current_venue` is a new read-only option that is set during `reprex_render()`. Other packages can use it to generate `reprex()`-compatible, `venue`-specific output.
+
 ## Dependency changes
 
 R 3.1 and R 3.2 are no longer explicitly supported or tested. Our general practice is to support the current release (4.0, at time of writing), devel, and the 4 previous versions of R (3.6, 3.5, 3.4, 3.3).

R/reprex-options.R

@@ -13,11 +13,13 @@
 #'   * `reprex.tidyverse_quiet`
 #'   * `reprex.std_out_err`
 #'
-#' A few more options exist, but are only consulted in specific situations:
-#'   * `reprex.venue`: Only consulted by [reprex_selection()]. [reprex()]
-#'     itself reveals the possible values for `venue` in the "Usage" section
-#'     of its help file and defaults to the first value, in the usual
-#'     [match.arg()] way.
+#' A few more options exist, but are only relevant to specific situations:
+#'   * `reprex.venue`: Can be used to control the `venue` used by the
+#'   [reprex_selection()] addin.
+#'   * `reprex.current_venue`: Read-only option that is set during
+#'   [reprex_render()]. Other packages that want to generate reprex-compatible
+#'   output can consult it via `getOption("reprex.current_venue")`, if they want
+#'   to tailor their output to the `venue`.
 #'   * `reprex.highlight.hl_style`: Only relevant to `venue = "rtf`. Details are
 #'     in the article
 #'     [reprex venue RTF](https://reprex.tidyverse.org/articles/articles/rtf.html).

R/reprex_render.R

@@ -86,7 +86,8 @@ reprex_render_impl <- function(input,
     rlang_trace_top_env = globalenv(),
     `rlang:::force_unhandled_error` = TRUE,
     rlang_backtrace_on_error = "full",
-    crayon.enabled = FALSE
+    crayon.enabled = FALSE,
+    reprex.current_venue = venue
   )
   if (new_session) {
     out <- tryCatch(

tests/testthat/test-reprex-options.R

@@ -0,0 +1,8 @@
+test_that("reprex.current_venue is set", {
+  skip_on_cran()
+  input <- "getOption('reprex.current_venue')"
+  ret <- reprex(input = paste0(input, "\n"))
+  expect_match(ret, "gh", all = FALSE)
+  ret <- reprex(input = paste0(input, "\n"), venue = "html")
+  expect_match(ret, "html", all = FALSE)
+})