fix #1717: signal an error if any files do not exist when included vi…

…a include_graphics()

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: knitr
 Type: Package
 Title: A General-Purpose Package for Dynamic Report Generation in R
-Version: 1.27
+Version: 1.27.1
 Authors@R: c(
     person("Yihui", "Xie", role = c("aut", "cre"), email = "[email protected]", comment = c(ORCID = "0000-0003-0645-5666")),
     person("Adam", "Vogt", role = "ctb"),

NEWS.md

@@ -1,3 +1,9 @@
+# CHANGES IN knitr VERSION 1.28
+
+## MINOR CHANGES
+
+- `include_graphics(files)` will signal an error if any `files` do not exist and are not web resources (thanks, @hadley, #1717).
+
 # CHANGES IN knitr VERSION 1.27
 
 ## NEW FEATURES

R/plot.R

@@ -375,6 +375,9 @@ include_graphics = function(
     path[i] = path2[i]
   }
   path = native_encode(path)
+  if (length(p <- path[!is_web_path(path) & !file.exists(path)])) stop(
+    'Cannot find the file(s): ', paste0('"', p, '"', collapse = '; ')
+  )
   structure(path, class = c('knit_image_paths', 'knit_asis'), dpi = dpi)
 }
 

R/utils.R

@@ -230,6 +230,11 @@ is_abs_path = function(x) {
   if (is_windows()) grepl('^(\\\\|[A-Za-z]:)', x) else grepl('^[/~]', x)
 }
 
+# paths of web resources?
+is_web_path = function(x) {
+  grepl('^(f|ht)tps?://', x)
+}
+
 # is tikz device without externalization?
 is_tikz_dev = function(options) {
   'tikz' %in% options$dev && !options$external