Rework output when caching directories (#559)

* Rework output when caching directories

This splits the logic when the buildpack saves and restores the cache
into two separate branches:

- when the user hasn't specified specific directories to cache (most everyone)
- when the user has given a list of specific directories to cache (power users)

This gives us more control over the default messaging, which has
included messaging for bower_components forever, even though most users
will never use bower, nor should we encourage them to.

These changes silence and minimize the messaging for the default case

bin/compile

@@ -9,7 +9,6 @@ unset GIT_DIR     # Avoid GIT_DIR leak from previous build steps
 
 ### Constants
 
-DEFAULT_CACHE="node_modules bower_components"
 BPLOG_PREFIX="buildpack.nodejs"
 
 ### Configure directories
@@ -141,6 +140,7 @@ install_bins | output "$LOG_FILE"
 
 restore_cache() {
   local cache_status="$(get_cache_status)"
+  local cache_directories="$(get_cache_directories)"
 
   if $YARN; then
     if [ -e "$BUILD_DIR/node_modules" ]; then
@@ -148,23 +148,38 @@ restore_cache() {
       rm -rf "$BUILD_DIR/node_modules"
     fi
   fi
-  if [ "$cache_status" == "valid" ]; then
-    local cache_directories=$(get_cache_directories)
-    if [ "$cache_directories" == "" ]; then
-      echo "Loading 2 from cacheDirectories (default):"
-      restore_cache_directories "$BUILD_DIR" "$CACHE_DIR" "$DEFAULT_CACHE"
+
+  if [[ "$cache_status" == "disabled" ]]; then
+    header "Restoring cache"
+    echo "Caching has been disabled because NODE_MODULES_CACHE=${NODE_MODULES_CACHE}"
+  elif [[ "$cache_status" == "valid" ]]; then
+    header "Restoring cache"
+    if [[ "$cache_directories" == "" ]]; then
+      restore_default_cache_directories "$BUILD_DIR" "$CACHE_DIR"
+    else
+      restore_custom_cache_directories "$BUILD_DIR" "$CACHE_DIR" $cache_directories
+    fi
+  elif [[ "$cache_status" == "new-signature" ]]; then
+    header "Restoring cache"
+    if [[ "$cache_directories" == "" ]]; then
+      echo "Cached directories were not restored because of a change in versions of node, npm, or yarn"
+      echo "Module installation may take longer for this build"
     else
-      echo "Loading $(echo $cache_directories | wc -w | xargs) from cacheDirectories (package.json):"
-      restore_cache_directories "$BUILD_DIR" "$CACHE_DIR" $cache_directories
+      # If the user has specified custom cache directories, be more explicit
+      echo "Invalidating cache due to a change in node, npm, or yarn versions"
+      echo "Will not restore the following directories for this build:"
+      for directory in $(< $cache_directories); do
+        echo "  $directory"
+      done
     fi
   else
-    echo "Skipping cache restore ($cache_status)"
+    # No cache exists, be silent
+    :
   fi
 
   mcount "cache.$cache_status"
 }
 
-header "Restoring cache" | output "$LOG_FILE"
 restore_cache | output "$LOG_FILE"
 
 build_dependencies() {
@@ -195,21 +210,21 @@ build_dependencies | output "$LOG_FILE"
 cache_build() {
   local cache_directories=$(get_cache_directories)
 
-  echo "Clearing previous node cache"
   clear_cache
   if ! ${NODE_MODULES_CACHE:-true}; then
-    echo "Skipping cache save (disabled by config)"
-  elif [ "$cache_directories" == "" ]; then
-    echo "Saving 2 cacheDirectories (default):"
-    save_cache_directories "$BUILD_DIR" "$CACHE_DIR" "$DEFAULT_CACHE"
+    # we've already warned that caching is disabled in the restore step
+    # so be silent here
+    :
+  elif [[ "$cache_directories" == "" ]]; then
+    header "Caching build"
+    save_default_cache_directories "$BUILD_DIR" "$CACHE_DIR"
   else
-    echo "Saving $(echo $cache_directories | wc -w | xargs) cacheDirectories (package.json):"
-    save_cache_directories "$BUILD_DIR" "$CACHE_DIR" $cache_directories
+    header "Caching build"
+    save_custom_cache_directories "$BUILD_DIR" "$CACHE_DIR" $cache_directories
   fi
   save_signature
 }
 
-header "Caching build"
 cache_build | output "$LOG_FILE"
 
 prune_devdependencies() {

lib/cache.sh

@@ -39,10 +39,34 @@ get_cache_directories() {
   fi
 }
 
-restore_cache_directories() {
+restore_default_cache_directories() {
   local build_dir=${1:-}
   local cache_dir=${2:-}
 
+  # node_modules
+  if [[ -e "$build_dir/node_modules" ]]; then
+    echo "- node_modules is checked into source control and cannot be cached"
+  elif [[ -e "$cache_dir/node/node_modules" ]]; then
+    echo "- node_modules"
+    mkdir -p $(dirname "$build_dir/node_modules")
+    mv "$cache_dir/node/node_modules" "$build_dir/node_modules"
+  else
+    echo "- node_modules (not cached - skipping)"
+  fi
+
+  # bower_components, should be silent if it is not in the cache
+  if [[ -e "$cache_dir/node/bower_components" ]]; then
+    echo "- bower_components"
+  fi
+}
+
+restore_custom_cache_directories() {
+  local build_dir=${1:-}
+  local cache_dir=${2:-}
+  local cache_directories="${@:3}"
+
+  echo "Loading $(echo $cache_directories | wc -w | xargs) from cacheDirectories (package.json):"
+
   for cachepath in ${@:3}; do
     if [ -e "$build_dir/$cachepath" ]; then
       echo "- $cachepath (exists - skipping)"
@@ -63,10 +87,37 @@ clear_cache() {
   mkdir -p $CACHE_DIR/node
 }
 
-save_cache_directories() {
+save_default_cache_directories() {
   local build_dir=${1:-}
   local cache_dir=${2:-}
 
+  # node_modules
+  if [[ -e "$build_dir/node_modules" ]]; then
+    echo "- node_modules"
+    mkdir -p "$cache_dir/node/node_modules"
+    cp -a "$build_dir/node_modules" $(dirname "$cache_dir/node/node_modules")
+  else
+    # this can happen if there are no dependencies
+    mcount "cache.no-node-modules"
+    echo "- node_modules (nothing to cache)"
+  fi
+
+  # bower_components
+  if [[ -e "$build_dir/bower_components" ]]; then
+    mcount "cache.saved-bower-components"
+    echo "- bower_components"
+    mkdir -p "$cache_dir/node/bower_components"
+    cp -a "$build_dir/bower_components" $(dirname "$cache_dir/node/bower_components")
+  fi
+}
+
+save_custom_cache_directories() {
+  local build_dir=${1:-}
+  local cache_dir=${2:-}
+  local cache_directories="${@:3}"
+
+  echo "Saving $(echo $cache_directories | wc -w | xargs) cacheDirectories (package.json):"
+
   for cachepath in ${@:3}; do
     if [ -e "$build_dir/$cachepath" ]; then
       echo "- $cachepath"

test/run

@@ -28,13 +28,11 @@ testDisableCache() {
 
   compile "node-modules-cache-2" $cache $env_dir
   assertCaptured "lodash@1.0.0"
-  assertCaptured "Saving 2 cacheDirectories"
   assertCapturedSuccess
 
   echo "false" > $env_dir/NODE_MODULES_CACHE
   compile "node-modules-cache-2" $cache $env_dir
   assertCaptured "lodash@1.3.1"
-  assertNotCaptured "Saving 2 cacheDirectories"
   assertCapturedSuccess
 }
 
@@ -42,9 +40,7 @@ testNodeModulesCached() {
   cache=$(mktmpdir)
 
   compile "caching" $cache
-  assertCaptured "Saving 2 cacheDirectories (default)"
   assertCaptured "- node_modules"
-  assertCaptured "- bower_components (nothing to cache)"
   assertEquals "1" "$(ls -1 $cache/node/node_modules | grep express | wc -l | tr -d ' ')"
   assertCapturedSuccess
 }
@@ -86,12 +82,12 @@ testBuildWithCache() {
   cache=$(mktmpdir)
 
   compile "stable-node" $cache
-  assertCaptured "Skipping cache restore (not-found)"
+  assertNotCaptured "Restoring cache"
   assertEquals "1" "$(ls -1 $cache/node/node_modules | grep hashish | wc -l | tr -d ' ')"
   assertCapturedSuccess
 
   compile "stable-node" $cache
-  assertNotCaptured "- node_modules (not cached - skipping)"
+  assertCaptured "- node_modules"
   assertFileContains "${STACK}" "${cache}/node/signature"
   assertCapturedSuccess
 
@@ -110,7 +106,7 @@ testCacheWithPrebuild() {
   assertCapturedSuccess
 
   compile "cache-prebuild" $cache $env_dir
-  assertCaptured "Skipping cache restore (new-signature"
+  assertCaptured "Cached directories were not restored because of a change in versions of node"
   assertCapturedSuccess
 }
 
@@ -451,7 +447,7 @@ testSignatureInvalidation() {
 
   compile "node-0.12.7" $cache
   assertCaptured "Downloading and installing node 0.12.7"
-  assertCaptured "Skipping cache restore (new-signature"
+  assertCaptured "Cached directories were not restored because of a change in versions of node"
   assertCapturedSuccess
 }