caching is an optional feature of knitr, so move digest to Suggests t…

…o make the dependencies a little lighter

DESCRIPTION

@@ -95,7 +95,6 @@ Depends:
     R (>= 3.1.0)
 Imports:
     evaluate (>= 0.10),
-    digest,
     highr,
     markdown,
     stringr (>= 0.6),
@@ -105,6 +104,7 @@ Imports:
 Suggests:
     formatR,
     testit,
+    digest,
     rgl (>= 0.95.1201),
     codetools,
     rmarkdown,

R/block.R

@@ -65,7 +65,7 @@ call_block = function(block) {
     if (params$engine == 'R' && isFALSE(params$cache.comments)) {
       content[['code']] = parse_only(content[['code']])
     }
-    hash = paste(valid_path(params$cache.path, label), digest::digest(content), sep = '_')
+    hash = paste(valid_path(params$cache.path, label), digest(content), sep = '_')
     params$hash = hash
     if (cache$exists(hash, params$cache.lazy) &&
         isFALSE(params$cache.rebuild) &&

R/plot.R

@@ -253,7 +253,7 @@ remove_plot = function(list, keep.high = TRUE) {
 # replace the content of the recorded plot with MD5 digests so that merge_plot()
 # will still work, and this will also save disk space for the case of cache=2
 digest_plot = function(x, level = 1) {
-  if (!is.list(x) || level >= 3) return(digest::digest(x))
+  if (!is.list(x) || level >= 3) return(digest(x))
   lapply(x, digest_plot, level = level + 1)
 }
 

R/utils.R

@@ -891,7 +891,7 @@ extract_raw_output = function(text, markers = raw_markers) {
   chunks = tokens = character(n)
   for (i in seq_len(n)) {
     chunks[i] = sub(r, '\\1', s[[1]][i])
-    tokens[i] = digest::digest(chunks[i])
+    tokens[i] = digest(chunks[i])
     s[[1]][i] = gsub(r, paste0(markers[1], tokens[i], markers[2]), s[[1]][i])
   }
   regmatches(x, m) = s
@@ -1003,3 +1003,10 @@ optipng = function(dir = '.') {
   files = list.files(dir, '[.]png$', recursive = TRUE, full.names = TRUE)
   for (f in files) system2('optipng', shQuote(f))
 }
+
+digest = function(...) {
+  if (!loadable('digest')) warning2(
+    'You used a knitr feature that depends on the digest package. Make sure it is installed.'
+  )
+  digest::digest(...)
+}