Patch the Pandoc LaTeX template instead of providing our own, which i…

…s too hard to maintain (#1563)

* Patch pandoc LaTeX template

Patch the pandoc LaTeX template to include the document subtitle (unnecessary with pandoc 2.6 onwards) using `--include-in-header` rather than overwriting its built-in template, avoiding compability problems with newer versions of pandoc. Closes #1510.

* Missing quotes

* Fix changelog typo

* Ensure self-contained is set for LaTeX

* Less verbose graphics setting

* move news of #1563 to v1.18

* cosmetic

* force --self-contained regardless of the template

* factor out pandoc_path_arg(rmarkdown_system_file(...)) to system_file_arg()

* support compact titles via a header include compact-title.tex

I didn't consider ef41eb4. I think it is a relatively minor issue and not worth the effort (if we have to bring it back, we need to test has_yaml_parameter(, 'author') and has_yaml_parameter(, 'date'), and conditionally include more titling hacks)

* mention the PR #252 which introduced the titling hacks

* cosmetic

* shouldn't change the value of the `template` argument when it is `default`

* add Andrew Dunning to the list of contributors

* also closes #1649

DESCRIPTION

@@ -15,6 +15,7 @@ Authors@R: c(
   person("Richard", "Iannone", role = "aut", email = "rich@rstudio.com", comment = c(ORCID = "0000-0003-3925-190X")),
   #
   # Contributors, ordered alphabetically by first name
+  person("Andrew", "Dunning", role = "ctb"),
   person("Atsushi", "Yasumoto", role = "ctb", comment = c(ORCID = "0000-0002-8335-495X")),
   person("Barret", "Schloerke", role = "ctb"),
   person("Christophe", "Dervieux", role = "ctb"),

NEWS.md

@@ -1,6 +1,8 @@
 rmarkdown 1.18
 ================================================================================
 
+- For `pdf_document()`, now we patch Pandoc's built-in LaTeX template to include the document subtitle (unnecessary with pandoc 2.6 onwards) and reduce the vertical spacing before title using `--include-in-header` rather than overwriting the built-in template, avoiding compability problems with newer versions of Pandoc (thanks, @adunning, #1563).
+
 - `find_external_resources()` works now when multiple files are specified in the `includes` option of the output format (thanks, @andrie, #1677).
 
 - `find_external_resources()` can find external resources specified in the output format's `reference_doc` or `reference_docx` option now (thanks, @jmcphers, #1696).

R/beamer_presentation.R

@@ -111,7 +111,7 @@ beamer_presentation <- function(toc = FALSE,
   args <- c(args, pandoc_highlight_args(highlight))
 
   # latex engine
-  latex_engine = match.arg(latex_engine, c("pdflatex", "lualatex", "xelatex"))
+  latex_engine <- match.arg(latex_engine, c("pdflatex", "lualatex", "xelatex"))
   args <- c(args, pandoc_latex_engine_args(latex_engine))
 
   # citation package

R/github_document.R

@@ -31,8 +31,8 @@ github_document <- function(toc = FALSE,
 
   # add special markdown rendering template to ensure we include the title fields
   pandoc_args <- c(
-    pandoc_args, "--template", pandoc_path_arg(rmarkdown_system_file(
-      "rmarkdown/templates/github_document/resources/default.md"))
+    pandoc_args, "--template", system_file_arg(
+      "rmarkdown/templates/github_document/resources/default.md")
   )
 
   pandoc2 <- pandoc2.0()
@@ -51,13 +51,13 @@ github_document <- function(toc = FALSE,
   if (html_preview) {
     format$post_processor <- function(metadata, input_file, output_file, clean, verbose) {
 
-      css <- pandoc_path_arg(rmarkdown_system_file(
-        "rmarkdown/templates/github_document/resources/github.css"))
+      css <- system_file_arg(
+        "rmarkdown/templates/github_document/resources/github.css")
       # provide a preview that looks like github
       args <- c(
         "--standalone", "--self-contained", "--highlight-style", "pygments",
-        "--template", pandoc_path_arg(rmarkdown_system_file(
-          "rmarkdown/templates/github_document/resources/preview.html")),
+        "--template", system_file_arg(
+          "rmarkdown/templates/github_document/resources/preview.html"),
         "--variable", paste0("github-markdown-css:", css),
         "--email-obfuscation", "none", # no email obfuscation
         if (pandoc2) c("--metadata", "pagetitle=PREVIEW")  # HTML5 requirement

R/html_document.R

@@ -260,11 +260,11 @@ html_document <- function(toc = FALSE,
   }
 
   # template path and assets
-  if (identical(template, "default"))
-    args <- c(args, "--template",
-              pandoc_path_arg(rmarkdown_system_file("rmd/h/default.html")))
-  else if (!is.null(template))
-    args <- c(args, "--template", pandoc_path_arg(template))
+  template_file <- if (identical(template, "default")) {
+    rmarkdown_system_file("rmd/h/default.html")
+  } else template
+  if (!is.null(template_file))
+    args <- c(args, "--template", pandoc_path_arg(template_file))
 
   # validate code_folding
   code_folding <- match.arg(code_folding)

R/ioslides_presentation.R

@@ -281,12 +281,9 @@ ioslides_presentation <- function(logo = NULL,
   args <- c(args, includes_to_pandoc_args(includes))
 
   # template path and assets
-  if (!is.null(template) && file.exists(template))
-    args <- c(args, "--template", template)
-  else
-    args <- c(args,
-              "--template",
-              pandoc_path_arg(rmarkdown_system_file("rmd/ioslides/default.html")))
+  if (is.null(template) || !file.exists(template))
+    template <- rmarkdown_system_file("rmd/ioslides/default.html")
+  args <- c(args, "--template", pandoc_path_arg(template))
 
   # html dependency for ioslides
   extra_dependencies <- append(extra_dependencies,

R/pdf_document.R

@@ -103,7 +103,7 @@ pdf_document <- function(toc = FALSE,
                          extra_dependencies = NULL) {
 
   # base pandoc options for all PDF output
-  args <- c()
+  args <- c("--self-contained")
 
   # table of contents
   args <- c(args, pandoc_toc_args(toc, toc_depth))
@@ -112,26 +112,14 @@ pdf_document <- function(toc = FALSE,
   if (identical(template, "default")) {
 
     pandoc_available(error = TRUE)
-    # choose the right template
+    # patch pandoc template if necessary
     version <- pandoc_version()
-    if (version >= "1.17.0.2")
-      latex_template <- "default-1.17.0.2.tex"
-    else if (version >= "1.15.2")
-      latex_template <- "default-1.15.2.tex"
-    else if (version >= "1.14")
-      latex_template <- "default-1.14.tex"
-    else
-      latex_template <- "default.tex"
-
-    # add to args
-    args <- c(args, "--template",
-              pandoc_path_arg(rmarkdown_system_file(paste0("rmd/latex/",
-                                                           latex_template))))
+    if (version <= "2.5") args <- c(
+      args, "--include-in-header", system_file_arg("rmd/latex/subtitle.tex")
+    )
 
   } else if (!is.null(template)) {
     args <- c(args, "--template", pandoc_path_arg(template))
-  } else {
-    args <- c(args, "--self-contained")
   }
 
   # numbered sections
@@ -144,7 +132,7 @@ pdf_document <- function(toc = FALSE,
   args <- c(args, pandoc_highlight_args(highlight))
 
   # latex engine
-  latex_engine = match.arg(latex_engine, c("pdflatex", "lualatex", "xelatex"))
+  latex_engine <- match.arg(latex_engine, c("pdflatex", "lualatex", "xelatex"))
   args <- c(args, pandoc_latex_engine_args(latex_engine))
 
   # citation package
@@ -155,7 +143,7 @@ pdf_document <- function(toc = FALSE,
   args <- c(args, includes_to_pandoc_args(includes))
 
   # make sure the graphics package is always loaded
-  if (identical(template, "default")) args <- c(args, "--variable", "graphics=yes")
+  if (identical(template, "default")) args <- c(args, "--variable", "graphics")
 
   # lua filters (added if pandoc > 2)
   args <- c(args, pandoc_lua_filters(c("pagebreak.lua", "latex-div.lua")))
@@ -185,8 +173,9 @@ pdf_document <- function(toc = FALSE,
         args <- c(args, "--variable", "geometry:margin=1in")
 
       # use titling package to change title format to be more compact by default
-      if (!has_yaml_parameter(input_test, "compact-title"))
-        args <- c(args, "--variable", "compact-title:yes")
+      if (!has_yaml_parameter(input_test, "compact-title")) args <- c(
+        args, "--include-in-header", system_file_arg("rmd/latex/compact-title.tex")
+      )
     }
 
     if (length(extra_dependencies) || has_latex_dependencies(knit_meta)) {

R/slidy_presentation.R

@@ -60,10 +60,8 @@ slidy_presentation <- function(incremental = FALSE,
 
   # template path and assets
   if (identical(template, "default"))
-    args <- c(args, "--template",
-              pandoc_path_arg(rmarkdown_system_file(
-                "rmd/slidy/default.html")))
-  else if (!is.null(template))
+    template <- rmarkdown_system_file("rmd/slidy/default.html")
+  if (!is.null(template))
     args <- c(args, "--template", pandoc_path_arg(template))
 
   # html dependency for slidy

R/util.R

@@ -37,6 +37,9 @@ rmarkdown_system_file <- function(...) {
   system.file(..., package = "rmarkdown")
 }
 
+system_file_arg <- function(...) {
+  pandoc_path_arg(rmarkdown_system_file(...))
+}
 
 #' @rdname rmarkdown_format
 #' @export

inst/rmd/latex/compact-title.tex

@@ -0,0 +1,16 @@
+% https://github.com/rstudio/rmarkdown/issues/337
+\let\rmarkdownfootnote\footnote%
+\def\footnote{\protect\rmarkdownfootnote}
+
+% https://github.com/rstudio/rmarkdown/pull/252
+\usepackage{titling}
+\setlength{\droptitle}{-2em}
+
+\pretitle{\vspace{\droptitle}\centering\huge}
+\posttitle{\par}
+
+\preauthor{\centering\large\emph}
+\postauthor{\par}
+
+\predate{\centering\large\emph}
+\postdate{\par}