Correctly pass pandoc_args between format function

fixes #564 and fix support of joss_article() for pdf_book() in bookdown

NEWS.md

@@ -1,5 +1,7 @@
 # rticles (development version)
 
+- `joss_article()` now correctly works as `base_format` for `bookdown::pdf_book()` (thanks, @mlysy, #564).
+
 - `oup_article()` now supports also `acknowledgments` in addition to `acknowledgements` as the original OUP LaTeX template (thanks, @dmkaplan2000, #563).
 
 - Update resources for `copernicus_article()` to version 7.7 from 3 January 2024.

R/joss_article.R

@@ -19,25 +19,21 @@
 joss_article <- function(journal = "JOSS",
                          keep_md = TRUE,
                          latex_engine = "xelatex",
+                         pandoc_args = NULL,
                          ...) {
   rmarkdown::pandoc_available("2.2", TRUE)
 
-  logo_path <- find_resource("joss", paste0(journal, "-logo.png"))
-  journalname <- ifelse(journal == "JOSS",
-    "Journal of Open Source Software",
-    "Journal of Open Source Education"
+  args <- list(
+    logo_path = find_resource("joss", paste0(journal, "-logo.png")),
+    journal_name = ifelse(journal == "JOSS", "Journal of Open Source Software", "Journal of Open Source Education"),
+    graphics = TRUE
   )
 
   pdf_document_format(
     "joss",
     latex_engine = latex_engine,
     citation_package = "default",
     keep_md = keep_md,
-    pandoc_args = c(
-      "-V", paste0("logo_path=", logo_path),
-      "-V", paste0("journal_name=", journalname),
-      "-V", "graphics=true"
-    ),
-    ...
-  )
+    pandoc_args = c(pandoc_args, list_to_pandoc_variable_args(args)),
+    ...)
 }