- faster processing of dependencies

NEWS.md

@@ -28,6 +28,8 @@
 
 - Fixed broken vignettes, improved CSS for HTML vignettes, and reduced the file sizes.
 
+- Faster processing of cache dependencies (thanks, @knokknok, #2318)
+
 # CHANGES IN knitr VERSION 1.45
 
 ## NEW FEATURES

R/block.R

@@ -345,7 +345,7 @@ eng_r = function(options) {
         objs, cache_globals(options$cache.globals, code), options$label,
         options$cache.path
       )
-      dep_auto()
+      dep_auto(chunk_label=options$label)
     }
     if (options$cache < 3) {
       if (options$cache.rebuild || !cache.exists) block_cache(options, res.orig, objs)

R/cache.R

@@ -142,6 +142,7 @@ cache_rx = '_[abcdef0123456789]{32}[.](rdb|rdx|RData)$'
 #' is similar to the effect of the \code{dependson} option. It is supposed to be
 #' used in the first chunk of a document and this chunk must not be cached.
 #' @param path Path to the dependency file.
+#' @param chunk_label The chunk label of the current code chunk.
 #' @return \code{NULL}. The dependencies are built as a side effect.
 #' @note Be cautious about \code{path}: because this function is used in a
 #'   chunk, the working directory when the chunk is evaluated is the directory
@@ -152,7 +153,7 @@ cache_rx = '_[abcdef0123456789]{32}[.](rdb|rdx|RData)$'
 #' @export
 #' @seealso \code{\link{dep_prev}}
 #' @references \url{https://yihui.org/knitr/demo/cache/}
-dep_auto = function(path = opts_chunk$get('cache.path')) {
+dep_auto = function(path = opts_chunk$get('cache.path'), chunk_label=NULL) {
   # this function should be evaluated in the original working directory
   owd = setwd(opts_knit$get('output.dir')); on.exit(setwd(owd))
   paths = valid_path(path, c('__objects', '__globals'))
@@ -164,8 +165,14 @@ dep_auto = function(path = opts_chunk$get('cache.path')) {
   }
   nms = intersect(names(knit_code$get()), names(locals)) # guarantee correct order
   # locals may contain old chunk names; the intersection can be of length < 2
-  if (length(nms) < 2) return(invisible(NULL))
-  for (i in 2:length(nms)) {
+  if (is.null(chunk_label)) {
+    if (length(nms) < 2) return(invisible(NULL))
+    chunk_ids <- 2:length(nms)
+  } else {
+    chunk_ids <- match(chunk_label, nms)
+    if (is.na(chunk_ids) || chunk_ids < 2) return(invisible(NULL))
+  }
+  for (i in chunk_ids) {
     if (length(g <- globals[[nms[i]]]) == 0) next
     for (j in 1:(i - 1L)) {
       # check if current globals are in old locals