Monkeypatch as.character.Rd to fix \href{} rendering

Fixes #778

Author: hadley

NEWS.md

@@ -1,5 +1,8 @@
 # roxygen2 (development version)
 
+* `\href{}` links in external inherited documentation are now inserted 
+  correctly (without additional `{}`) (#778).
+
 * White space is automatically trimmed off the `RoxygenNote` field when 
   comparing the installed version of roxygen2 to the version used to 
   generate the documentation (#802).

R/utils-rd.R

@@ -73,7 +73,37 @@ get_tags <- function(rd, tag) {
 }
 
 rd2text <- function(x) {
-  chr <- as.character(structure(x, class = "Rd"), deparse = TRUE)
+  chr <- as_character_rd(structure(x, class = "Rd"), deparse = TRUE)
   paste(chr, collapse = "")
 }
 
+
+# helpers -----------------------------------------------------------------
+
+parse_rd <- function(x) {
+  con <- textConnection(x)
+  on.exit(close(con), add = TRUE)
+
+  tryCatch(
+    tools::parse_Rd(con, fragment = TRUE, encoding = "UTF-8"),
+    warning = function(cnd) NULL
+  )
+}
+
+# Generated in .onLoad()
+as_character_rd <- NULL
+make_as_character_rd <- function() {
+  # "as.character.Rd" appears to be missing \href in TWOARGS
+  # this code hacks the body of the function to add it
+  fn <- internal_f("tools", "as.character.Rd")
+
+  body <- body(fn)
+  idx <- purrr::detect_index(body, ~ is_call(.x, "<-", 2) && is_symbol(.x[[2]], "TWOARG"))
+  if (idx == 0) {
+    return(fn)
+  }
+
+  body[[idx]][[3]] <- call_modify(body[[idx]][[3]], "\\href")
+  body(fn) <- body
+  fn
+}

R/zzz.R

@@ -0,0 +1,3 @@
+.onLoad <- function(...) {
+  as_character_rd <<- make_as_character_rd()
+}

tests/testthat/test-utils-rd.R

@@ -0,0 +1,3 @@
+test_that("href doesn't get extra parens", {
+  expect_equal(rd2text(parse_rd("\\href{a}{b}")), "\\href{a}{b}\n")
+})