fall back to html_document for default_output_format() if output format can't be recognized in YAML (this is mainly used in RStudio IDE)

Author: yihui

DESCRIPTION

@@ -1,7 +1,7 @@
 Type: Package
 Package: rmarkdown
 Title: Dynamic Documents for R
-Version: 2.30.2
+Version: 2.30.3
 Authors@R: c(
     person("JJ", "Allaire", , "jj@posit.co", role = "aut"),
     person("Yihui", "Xie", , "xie@yihui.name", role = c("aut", "cre"), comment = c(ORCID = "0000-0003-0645-5666")),

NEWS.md

@@ -5,6 +5,8 @@ rmarkdown 2.31
 
 - Use the argument `--syntax-highlighting` for Pandoc >= 3.8 since `--highlight-style` has been deprecated (thanks, @ywwry66, #2602).
 
+- `default_output_format()` will fall back to `html_document` if the output format in YAML cannot be recognized.
+
 
 rmarkdown 2.30
 ================================================================================

R/output_format.R

@@ -436,7 +436,12 @@ default_output_format <- function(input, output_yaml = NULL) {
 
   # look up the formals of the output function to get the full option list and
   # merge against the explicitly set list
-  format_function <- eval(xfun::parse_only(format$name))
+  format_function <- tryCatch(
+    eval(xfun::parse_only(format$name)), error = function(e) NULL
+  )
+  # if we can't find the function, default to html_document with no options
+  if (!is.function(format_function))
+    return(list(name = "html_document", options = list()))
   format$options <- merge_lists(as.list(formals(format_function)),
                                 format$options,
                                 recursive = FALSE)