fix #2043: replace parse(text) with xfun::parse_only() to avoid hanging the R session when the input is empty

also signal an error if the `site` field is not a function

Author: yihui

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: rmarkdown
 Type: Package
 Title: Dynamic Documents for R
-Version: 2.8.2
+Version: 2.8.3
 Authors@R: c(
   person("JJ", "Allaire", role = "aut", email = "jj@rstudio.com"),
   person("Yihui", "Xie", role = c("aut", "cre"), email = "xie@yihui.name", comment = c(ORCID = "0000-0003-0645-5666")),

NEWS.md

@@ -5,6 +5,8 @@ rmarkdown 2.9
 
 - Floating ToC in `html_document` can now hide headings with unnumbered and unlisted classes (thanks, @atusy, #1993).
 
+- `rmarkdown::site_generator()` can hang session waiting for input when the `site` field is not found in the YAML frontmatter of `index.Rmd` (thanks, @kevinushey @mirh, #2043).
+
 
 rmarkdown 2.8
 ================================================================================

R/html_resources.R

@@ -332,7 +332,7 @@ discover_rmd_resources <- function(rmd_file, discover_single_resource) {
   # html_document to pick up dependencies
   output_format <- output_format_from_yaml_front_matter(rmd_content)
 
-  output_format_function <- eval(parse(text = output_format$name))
+  output_format_function <- eval(xfun::parse_only(output_format$name))
 
   override_output_format <- if (!is_pandoc_to_html(output_format_function()$pandoc)) "html_document"
 

R/output_format.R

@@ -402,7 +402,7 @@ 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(parse(text = format$name))
+  format_function <- eval(xfun::parse_only(format$name))
   format$options <- merge_lists(as.list(formals(format_function)),
                                 format$options,
                                 recursive = FALSE)
@@ -615,7 +615,7 @@ output_format_string_from_ext <- function(output_file) {
 }
 
 create_output_format_function <- function(name) {
-  output_format_func <- eval(parse(text = name))
+  output_format_func <- eval(xfun::parse_only(name))
   if (!is.function(output_format_func))
     stop("YAML output format must evaluate to a function", call. = FALSE)
   output_format_func

R/render_site.R

@@ -282,7 +282,11 @@ site_generator <- function(input = ".", output_format = NULL) {
   front_matter <- yaml_front_matter(index)
 
   # create the site generator (passing the root dir)
-  create_site_generator <- eval(parse(text = front_matter$site))
+  create_site_generator <- eval(xfun::parse_only(front_matter$site))
+  if (!is.function(create_site_generator)) stop(
+    "Cannot find the site generator from the 'site' field in YAML frontmatter ",
+    "of '", index, "'."
+  )
   generator <- create_site_generator(root)
 
   # if it's in a subdir check to see if the generator supports nested files

R/shiny_prerendered.R

@@ -28,7 +28,7 @@ shiny_prerendered_app <- function(input_rmd, render_args) {
     assign(".shiny_prerendered_server_start_code", server_start_code, envir = server_envir)
 
     # execute the startup code (server_start_context + context="data" loading)
-    eval(parse(text = server_start_context), envir = server_envir)
+    eval(xfun::parse_only(server_start_context), envir = server_envir)
     shiny_prerendered_data_load(input_rmd, server_envir)
 
     # lock the environment to prevent inadvertant assignments
@@ -39,7 +39,7 @@ shiny_prerendered_app <- function(input_rmd, render_args) {
   .server_context <- shiny_prerendered_extract_context(html_lines, "server")
   server_envir$.server_context <- .server_context
   server <- function(input, output, session) {
-    eval(parse(text = .server_context))
+    eval(xfun::parse_only(.server_context))
   }
   environment(server) <- new.env(parent = server_envir)
 
@@ -521,7 +521,7 @@ shiny_prerendered_evaluate_hook <- function(input) {
 
     # otherwise parse so we can throw an error for invalid code
     else {
-      parse(text = code)
+      xfun::parse_only(code)
       list()
     }
   }