file_scope is now correctly merged when creating output_format

DESCRIPTION

@@ -1,7 +1,7 @@
 Type: Package
 Package: rmarkdown
 Title: Dynamic Documents for R
-Version: 2.23.1
+Version: 2.23.2
 Authors@R: c(
     person("JJ", "Allaire", , "[email protected]", role = "aut"),
     person("Yihui", "Xie", , "[email protected]", role = c("aut", "cre"), comment = c(ORCID = "0000-0003-0645-5666")),

NEWS.md

@@ -1,7 +1,7 @@
 rmarkdown 2.24
 ================================================================================
 
-
+- Fixed `file_scope` being lost when extending output formats that considers the `file_scope` using `output_format()`. Merge behavior is to apply overlay `file_scope` function onto the result of `base_format`'s `file_scope` function. This implies that `file_scope` gains second argument which receives the returned values of the base `file_scope` (thanks, @atusy, #2488).
 
 rmarkdown 2.23
 ================================================================================

R/output_format.R

@@ -52,9 +52,11 @@
 #' @param file_scope A function that will split markdown input to pandoc into
 #'   multiple named files. This is useful when the caller has concatenated a set
 #'   of Rmd files together (as \pkg{bookdown} does), and those files may need to
-#'   processed by pandoc using the \code{--file-scope} option. The function
-#'   should return a named list of files w/ \code{name} and \code{content} for
-#'   each file.
+#'   processed by pandoc using the \code{--file-scope} option. The first
+#'   argument is input file paths and the second is \code{NULL} or current file
+#'   scope which is a named list of files w/ \code{name} and \code{content} for
+#'   each file. The return is the new file scope. Also, the arguments should
+#'   include \code{...} for the future extensions.
 #' @param base_format An optional format to extend.
 #' @return An R Markdown output format definition that can be passed to
 #'   \code{\link{render}}.
@@ -157,6 +159,27 @@ merge_post_processors <- function(base,
   }
 }
 
+merge_file_scope <- function(base,
+                             overlay) {
+  if (is.null(overlay)) {
+    return(base)
+  }
+  has_ellipsis <- "..." %in% names(formals(overlay))
+  if (!has_ellipsis) {
+    warning("file_scope lacks ... as an argument. ",
+            "Otherwise, file_scope replaces file_scope without merging.")
+  }
+  if (is.null(base) || !has_ellipsis) {
+    return(overlay)
+  }
+  if (has_ellipsis) {
+    return(function(x, current_scope = NULL, ...) {
+      scope <- base(x, current_scope, ...)
+      overlay(x, scope, ...)
+    })
+  }
+}
+
 # merges two output formats
 merge_output_formats <- function(base,
                                  overlay) {
@@ -181,6 +204,7 @@ merge_output_formats <- function(base,
                              overlay$intermediates_generator, c),
     post_processor =
       merge_post_processors(base$post_processor, overlay$post_processor),
+    file_scope = merge_file_scope(base$file_scope, overlay$file_scope),
     on_exit =
       merge_on_exit(base$on_exit, overlay$on_exit)
   ), class = "rmarkdown_output_format")

R/render.R

@@ -1200,7 +1200,11 @@ resolve_df_print <- function(df_print) {
 output_metadata = knitr:::new_defaults()
 
 file_scope_split <- function(input, fun) {
-  inputs <- fun(input)
+  inputs <- if (length(formals(fun)) == 1L) {
+    fun(input) # for the backward compatibility
+  } else {
+    fun(input, NULL) # the second argument implies current file scope
+  }
 
   # file_scope_fun should split the input file in several
   # do nothing if not and return input file unsplited

tests/testthat/test-output_format.R

@@ -7,6 +7,7 @@ test_that("all elements can be NULL", {
 
 test_that("inherits base format", {
   base_fmt <- html_document()
+  base_fmt$file_scope <- identity
   out_fmt <- output_format(
     knitr = NULL, pandoc = NULL, keep_md = NULL, clean_supporting = NULL,
     base_format = base_fmt
@@ -17,6 +18,23 @@ test_that("inherits base format", {
   expect_identical(out_fmt[not_fun], base_fmt[not_fun])
 })
 
+test_that("file_scope replaces base format", {
+  base_fmt <- html_document()
+  base_fmt$file_scope <- function(input_file, file_scope, ...) {
+    return(list("foo" = "foo"))
+  }
+  out_fmt <- output_format(
+    knitr = NULL, pandoc = NULL, keep_md = NULL, clean_supporting = NULL,
+    file_scope = function(input_file, file_scope, ...) {
+      file_scope$bar <- "bar"
+      return(file_scope)
+    },
+    base_format = base_fmt
+  )
+  expect_identical(out_fmt$file_scope("input", NULL),
+                   list("foo" = "foo", "bar" = "bar"))
+})
+
 test_that("clean_supporting is coerced to FALSE only if keep_md is TRUE", {
   args_combinations <- expand.grid(
     knitr = list(NULL),