Add alternative command to run npm ci with cache

bin/install_npm_packages

@@ -2,13 +2,13 @@
 
 # Ensure package.json is present
 if [ ! -f package.json ]; then
-    echo "No valid package.json file found"
+    echo "No package.json found!"
     exit 1
 fi
 
-# Ensure package-lock.json is present 
+# Ensure package-lock.json is present
 if [ ! -f package-lock.json ]; then
-    echo "No valid package-lock.json file found"
+    echo "No package-lock.json found!"
     exit 1
 fi
 

bin/install_npm_packages_clean

@@ -0,0 +1,70 @@
+#!/bin/bash -eu
+
+# Ensure package.json is present
+if [ ! -f package.json ]; then
+    echo "No package.json found!"
+    exit 1
+fi
+
+# Ensure package-lock.json is present
+if [ ! -f package-lock.json ]; then
+    echo "No package-lock.json found!"
+    exit 1
+fi
+
+PLATFORM=$(uname -s)
+ARCHITECTURE=$(uname -m)
+NODE_VERSION=$(node --version)
+PACKAGE_HASH=$(hash_file package-lock.json)
+
+# See https://www.npmjs.com/package/patch-package#circleci
+if [ -d patches ]; then
+  PATCHES_HASH=$(hash_directory patches/)
+else
+  PATCHES_HASH=nopatch
+fi
+
+CACHEKEY="$BUILDKITE_PIPELINE_SLUG-npm-$PLATFORM-$ARCHITECTURE-node-$NODE_VERSION-$PACKAGE_HASH-$PATCHES_HASH"
+
+LOCAL_NPM_CACHE=./vendor/npm
+mkdir -p $LOCAL_NPM_CACHE
+echo "--- :npm: Set npm to use $LOCAL_NPM_CACHE for cache"
+npm set cache $LOCAL_NPM_CACHE
+echo "npm cache set to $(npm get cache)"
+
+echo "--- :npm: Restore npm cache if present"
+restore_cache "$CACHEKEY"
+
+echo "--- :npm: Install Node dependencies"
+
+# To avoid constant ECONNRESET errors a limit is set for Linux,
+# as this is not happening with the Mac jobs.
+# This issue is being tracked here:
+# https://github.com/npm/cli/issues/4652
+if [ "$PLATFORM" = "Linux" ]; then
+  MAX_SOCKETS=1
+else
+  # Default value from npm.
+  # TODO: Link to source
+  MAX_SOCKETS=15
+fi
+
+npm ci \
+  --unsafe-perm \
+  --prefer-offline \
+  --no-audit \
+  --no-progress \
+  --maxsockets "$MAX_SOCKETS" \
+  "$@" # TODO: Use approach from other commands where only a subset of flags are allowed
+
+echo "--- :npm: Save cache if necessary"
+# Notice that we don't cache the local node_modules.
+# Those get regenerated by npm ci as per Node reccomendations.
+# What we are caching is the root npm folder, which stores pacakge downloads so they are available if the package.json resolution demands them.
+#
+# npm stores temporary files in its cache that we don't want to extract because they might run into naming conflicts.
+# So, before archiving it, we remove those tmp files.
+#
+# Example: https://buildkite.com/automattic/gutenberg-mobile/builds/8857#018e37eb-7afc-4280-b736-cba76f02f1a3/524
+rm -rf "$LOCAL_NPM_CACHE/_cacache/tmp"
+save_cache "$LOCAL_NPM_CACHE" "$CACHEKEY"