Cache stack

bin/compile

@@ -29,6 +29,17 @@ function indent() {
   esac
 }
 
+# Store which STACK we are running on in the cache to bust the cache if it changes
+if [ -f $CACHE_DIR/.apt/STACK ]; then
+  CACHED_STACK=$(cat "$CACHE_DIR/.apt/STACK")
+else
+  CACHED_STACK=$STACK
+fi
+
+# Ensure we store the STACK in the cache for next time.
+mkdir -p "$CACHE_DIR/.apt"
+echo "$STACK" > "$CACHE_DIR/.apt/STACK"
+
 APT_CACHE_DIR="$CACHE_DIR/apt/cache"
 APT_STATE_DIR="$CACHE_DIR/apt/state"
 APT_SOURCELIST_DIR="$CACHE_DIR/apt/sources"   # place custom sources.list here
@@ -42,12 +53,12 @@ case "$APT_VERSION" in
   *)         APT_FORCE_YES="--allow-downgrades --allow-remove-essential --allow-change-held-packages";;
 esac
 
-if [ -f $APT_CACHE_DIR/Aptfile ] && cmp -s $BUILD_DIR/Aptfile $APT_CACHE_DIR/Aptfile ; then
-  # Old Aptfile is the same as new
+if [ -f $APT_CACHE_DIR/Aptfile ] && cmp -s $BUILD_DIR/Aptfile $APT_CACHE_DIR/Aptfile && [[ $CACHED_STACK == $STACK ]] ; then
+  # Old Aptfile is the same as new and STACK has not changed
   topic "Reusing cache"
 else
-  # Aptfile changed or does not exist
-  topic "Detected Aptfile changes, flushing cache"
+  # Aptfile changed or does not exist or STACK changed
+  topic "Detected Aptfile or Stack changes, flushing cache"
   rm -rf $APT_CACHE_DIR
   mkdir -p "$APT_CACHE_DIR/archives/partial"
   mkdir -p "$APT_STATE_DIR/lists/partial"

test/compile_test.sh

@@ -3,11 +3,7 @@
 . ${BUILDPACK_TEST_RUNNER_HOME}/lib/test_utils.sh
 
 testCompile() {
-  cat > ${BUILD_DIR}/Aptfile <<EOF
-# Test comment
-s3cmd
-wget
-EOF
+  loadFixture "Aptfile"
 
   compile
 
@@ -18,3 +14,46 @@ EOF
   assertCaptured "Fetching .debs for wget"
   assertCaptured "Installing wget_"
 }
+
+testStackChange() {
+  loadFixture "Aptfile"
+
+  #Set the cached STACK value to a non-existent stack, so it is guaranteed to change.
+  mkdir -p "$CACHE_DIR/.apt/"
+  echo "cedar-10" > "$CACHE_DIR/.apt/STACK"
+
+  #Load the Aptfile into the cache, to exclusively test the stack changes
+  mkdir -p "$CACHE_DIR/apt/cache"
+  cp $BUILD_DIR/Aptfile "$CACHE_DIR/apt/cache"
+
+  compile
+
+  assertCapturedSuccess
+
+  assertCaptured "Detected Aptfile or Stack changes, flushing cache"
+}
+
+testStackNoChange() {
+  loadFixture "Aptfile"
+
+  #Load the Aptfile into the cache, to exclusively test the stack changes
+  mkdir -p "$CACHE_DIR/apt/cache"
+  cp $BUILD_DIR/Aptfile "$CACHE_DIR/apt/cache"
+
+  compile
+
+  assertCaptured "Reusing cache"
+}
+
+testStackCached() {
+  loadFixture "Aptfile"
+
+  compile
+  assertCapturedSuccess
+
+  assertTrue 'STACK not cached' "[ -e $CACHE_DIR/.apt/STACK ]"
+}
+
+loadFixture() {
+  cp -a $BUILDPACK_HOME/test/fixtures/$1/. ${BUILD_DIR}
+}

test/fixtures/Aptfile/Aptfile

@@ -0,0 +1,3 @@
+# Test comment
+s3cmd
+wget