Port Buildpack author guide to NodeJS

Simplify the buildpack author guide, using NodeJS instead of Ruby.
The switch to NodeJS makes multi-arch demos more striaghtforward

Signed-off-by: Aidan Delaney <[email protected]>

Author: AidanDelaney

content/docs/buildpack-author-guide/create-buildpack/adding-bill-of-materials.md

@@ -17,7 +17,7 @@ You can find some of this information using `pack` via its `inspect-image` comma
 
 <!-- test:exec -->
 ```bash
-pack inspect-image test-ruby-app
+pack inspect-image test-node-js-app
 ```
 <!--+- "{{execute}}"+-->
 You should see the following:
@@ -30,28 +30,27 @@ Run Images:
 
 Buildpacks:
   ID                   VERSION        HOMEPAGE
-  examples/ruby        0.0.1          -
+  examples/node-js        0.0.1          -
 
 Processes:
   TYPE                 SHELL        COMMAND                           ARGS        WORK DIR
-  web (default)        bash         bundle exec ruby app.rb                       /workspace
-  worker               bash         bundle exec ruby worker.rb                    /workspace
+  web (default)        bash         node-js app.js                                   /workspace
 ```
 
-Apart from the above standard metadata, buildpacks can also populate information about the dependencies they have provided in form of a `Bill-of-Materials`. Let's see how we can use this to populate information about the version of `ruby` that was installed in the output app image.
+Apart from the above standard metadata, buildpacks can also populate information about the dependencies they have provided in form of a `Bill-of-Materials`. Let's see how we can use this to populate information about the version of `node-js` that was installed in the output app image.
 
-To add the `ruby` version to the output of `pack download sbom`, we will have to provide a [Software `Bill-of-Materials`](https://en.wikipedia.org/wiki/Software_bill_of_materials) (`SBOM`) containing this information. There are three "standard" ways to report SBOM data.  You'll need to choose to use one of [CycloneDX](https://cyclonedx.org/), [SPDX](https://spdx.dev/) or [Syft](https://github.com/anchore/syft) update the `ruby.sbom.<ext>` (where `<ext>` is the extension appropriate for your SBOM standard, one of `cdx.json`, `spdx.json` or `syft.json`) at the end of your `build` script.  Discussion of which SBOM format to choose is outside the scope of this tutorial, but we will note that the SBOM format you choose to use is likely to be the output format of any SBOM scanner (eg: [`syft cli`](https://github.com/anchore/syft)) you might choose to use.  In this example we will use the CycloneDX json format.
+To add the `node-js` version to the output of `pack download sbom`, we will have to provide a [Software `Bill-of-Materials`](https://en.wikipedia.org/wiki/Software_bill_of_materials) (`SBOM`) containing this information. There are three "standard" ways to report SBOM data.  You'll need to choose to use one of [CycloneDX](https://cyclonedx.org/), [SPDX](https://spdx.dev/) or [Syft](https://github.com/anchore/syft) update the `node-js.sbom.<ext>` (where `<ext>` is the extension appropriate for your SBOM standard, one of `cdx.json`, `spdx.json` or `syft.json`) at the end of your `build` script.  Discussion of which SBOM format to choose is outside the scope of this tutorial, but we will note that the SBOM format you choose to use is likely to be the output format of any SBOM scanner (eg: [`syft cli`](https://github.com/anchore/syft)) you might choose to use.  In this example we will use the CycloneDX json format.
 
 First, annotate the `buildpack.toml` to specify that it emits CycloneDX:
 
-<!-- test:file=ruby-buildpack/buildpack.toml -->
+<!-- test:file=node-js-buildpack/buildpack.toml -->
 ```toml
 # Buildpack API version
 api = "0.8"
 
 # Buildpack ID and metadata
 [buildpack]
-  id = "examples/ruby"
+  id = "examples/node-js"
   version = "0.0.1"
   sbom-formats = [ "application/vnd.cyclonedx+json" ]
 
@@ -69,177 +68,136 @@ Then, in our buildpack implementation we will generate the necessary SBOM metada
 ```bash
 # ...
 
-# Append a Bill-of-Materials containing metadata about the provided ruby version
-cat >> "$layersdir/ruby.sbom.cdx.json" << EOL
+# Append a Bill-of-Materials containing metadata about the provided node-js version
+cat >> "${layersdir}/node-js.sbom.cdx.json" << EOL
 {
   "bomFormat": "CycloneDX",
   "specVersion": "1.4",
   "version": 1,
   "components": [
     {
       "type": "library",
-      "name": "ruby",
-      "version": "$ruby_version"
+      "name": "node-js",
+      "version": "$node-js_version"
     }
   ]
 }
 EOL
 ```
 
-We can also add an SBOM entry for each dependency listed in `Gemfile.lock`.  Here we use `jq` to add a new record to the `components` array in `bundler.sbom.cdx.json`:
+We can also add an SBOM entry for each dependency listed in `package.json`.  Here we use `jq` to add a new record to the `components` array in `bundler.sbom.cdx.json`:
 
 ```bash
-crubybom="${layersdir}/ruby.sbom.cdx.json"
-cat >> ${rubybom} << EOL
+cnode-jsbom="${layersdir}/node-js.sbom.cdx.json"
+cat >> ${node-jsbom} << EOL
 {
   "bomFormat": "CycloneDX",
   "specVersion": "1.4",
   "version": 1,
   "components": [
     {
       "type": "library",
-      "name": "ruby",
-      "version": "$ruby_version"
+      "name": "node-js",
+      "version": "$node-js_version"
     }
   ]
 }
 EOL
-if [[ -f Gemfile.lock ]] ; then
+if [[ -f package.json ]] ; then
   for gem in $(gem dep -q | grep ^Gem | sed 's/^Gem //')
   do
     version=${gem##*-}
     name=${gem%-${version}}
     DEP=$(jq --arg name "${name}" --arg version "${version}" \
       '.components[.components| length] |= . + {"type": "library", "name": $name, "version": $version}' \
-      "${rubybom}")
-    echo ${DEP} > "${rubybom}"
+      "${node-jsbom}")
+    echo ${DEP} > "${node-jsbom}"
   done
 fi
 ```
 
-Your `ruby-buildpack/bin/build`<!--+"{{open}}"+--> script should look like the following:
+Your `node-js-buildpack/bin/build`<!--+"{{open}}"+--> script should look like the following:
 
-<!-- test:file=ruby-buildpack/bin/build -->
+<!-- test:file=node-js-buildpack/bin/build -->
 ```bash
 #!/usr/bin/env bash
 set -eo pipefail
 
-echo "---> Ruby Buildpack"
+echo "---> NodeJS Buildpack"
 
 # 1. GET ARGS
 layersdir=$1
 plan=$3
 
 # 2. CREATE THE LAYER DIRECTORY
-rubylayer="$layersdir"/ruby
-mkdir -p "$rubylayer"
-
-# 3. DOWNLOAD RUBY
-ruby_version=$(cat "$plan" | yj -t | jq -r '.entries[] | select(.name == "ruby") | .metadata.version')
-echo "---> Downloading and extracting Ruby $ruby_version"
-ruby_url=https://s3-external-1.amazonaws.com/heroku-buildpack-ruby/heroku-22/ruby-$ruby_version.tgz
-wget -q -O - "$ruby_url" | tar -xzf - -C "$rubylayer"
-
-# 4. MAKE RUBY AVAILABLE DURING LAUNCH
-echo -e '[types]\nlaunch = true' > "$layersdir/ruby.toml"
-
-# 5. MAKE RUBY AVAILABLE TO THIS SCRIPT
-export PATH="$rubylayer"/bin:$PATH
-export LD_LIBRARY_PATH=${LD_LIBRARY_PATH:+${LD_LIBRARY_PATH}:}"$rubylayer/lib"
-
-# 6. INSTALL GEMS
-# Compares previous Gemfile.lock checksum to the current Gemfile.lock
-bundlerlayer="$layersdir/bundler"
-local_bundler_checksum=$((sha256sum Gemfile.lock || echo 'DOES_NOT_EXIST') | cut -d ' ' -f 1)
-remote_bundler_checksum=$(cat "$layersdir/bundler.toml" | yj -t | jq -r .metadata.checksum 2>/dev/null || echo 'DOES_NOT_EXIST')
-# Always set the types table so that we re-use the appropriate layers
-echo -e '[types]\ncache = true\nlaunch = true' >> "$layersdir/bundler.toml"
-
-if [[ -f Gemfile.lock && $local_bundler_checksum == $remote_bundler_checksum ]] ; then
-    # Determine if no gem dependencies have changed, so it can reuse existing gems without running bundle install
-    echo "---> Reusing gems"
-    bundle config --local path "$bundlerlayer" >/dev/null
-    bundle config --local bin "$bundlerlayer/bin" >/dev/null
-else
-    # Determine if there has been a gem dependency change and install new gems to the bundler layer; re-using existing and un-changed gems
-    echo "---> Installing gems"
-    mkdir -p "$bundlerlayer"
-    cat >> "$layersdir/bundler.toml" << EOL
-[metadata]
-checksum = "$local_bundler_checksum"
-EOL
-    bundle config set --local path "$bundlerlayer" && bundle install && bundle binstubs --all --path "$bundlerlayer/bin"
+node-js_layer="${layersdir}"/node-js
+mkdir -p "${node-js_layer}"
 
-fi
+# 3. DOWNLOAD node-js
+node-js_version=$(cat "$plan" | yj -t | jq -r '.entries[] | select(.name == "node-js") | .metadata.version')
+echo "---> Downloading and extracting NodeJS"
+node-js_url=https://nodejs.org/dist/v18.18.1/node-v18.18.1-linux-x64.tar.xz
+wget -q -O - "$node-js_url" | tar -xxf - -C "${node-js_layer}"
+
+# 4. MAKE node-js AVAILABLE DURING LAUNCH
+echo -e '[types]\nlaunch = true' > "${layersdir}/node-js.toml"
+
+# 5. MAKE node-js AVAILABLE TO THIS SCRIPT
+export PATH="${node-js_layer}"/bin:$PATH
+export LD_LIBRARY_PATH=${LD_LIBRARY_PATH:+${LD_LIBRARY_PATH}:}"${node-js_layer}/lib"
 
-# 7. SET DEFAULT START COMMAND
-cat > "$layersdir/launch.toml" << EOL
+# 6. SET DEFAULT START COMMAND
+cat > "${layersdir}/launch.toml" << EOL
 # our web process
 [[processes]]
 type = "web"
-command = "bundle exec ruby app.rb"
+command = "node app.js"
 default = true
-
-# our worker process
-[[processes]]
-type = "worker"
-command = "bundle exec ruby worker.rb"
 EOL
 
 # ========== ADDED ===========
-# 8. ADD A SBOM
-rubybom="${layersdir}/ruby.sbom.cdx.json"
-cat >> ${rubybom} << EOL
+# 7. ADD A SBOM
+node-jsbom="${layersdir}/node-js.sbom.cdx.json"
+cat >> ${node-jsbom} << EOL
 {
   "bomFormat": "CycloneDX",
   "specVersion": "1.4",
   "version": 1,
   "components": [
     {
       "type": "library",
-      "name": "ruby",
-      "version": "$ruby_version"
+      "name": "node-js",
+      "version": "$node-js_version"
     }
   ]
 }
 EOL
-if [[ -f Gemfile.lock ]] ; then
-  for gem in $(gem dep -q | grep ^Gem | sed 's/^Gem //')
-  do
-    version=${gem##*-}
-    name=${gem%-${version}}
-    DEP=$(jq --arg name "${name}" --arg version "${version}" \
-      '.components[.components| length] |= . + {"type": "library", "name": $name, "version": $version}' \
-      "${rubybom}")
-    echo ${DEP} > "${rubybom}"
-  done
-fi
 ```
 
 Then rebuild your app using the updated buildpack:
 
 <!-- test:exec -->
 ```bash
-pack build test-ruby-app --path ./ruby-sample-app --buildpack ./ruby-buildpack
+pack build test-node-js-app --path ./node-js-sample-app --buildpack ./node-js-buildpack
 ```
 <!--+- "{{execute}}"+-->
 
 Viewing your bill-of-materials requires extracting (or `download`ing) the bill-of-materials from your local image.  This command can take some time to return.
 
 <!-- test:exec -->
 ```bash
-pack sbom download test-ruby-app
+pack sbom download test-node-js-app
 ```
 <!--+- "{{execute}}"+-->
 
 The SBOM information is now downloaded to the local file system:
 
 <!-- test:exec -->
 ```bash
-cat layers/sbom/launch/examples_ruby/ruby/sbom.cdx.json | jq -M
+cat layers/sbom/launch/examples_node-js/node-js/sbom.cdx.json | jq -M
 ```
 
-You should find that the included `ruby` version is `3.1.0` as expected.
+You should find that the included `node-js` version is `3.1.0` as expected.
 
 <!-- test:assert=contains;ignore-lines=... -->
 ```text
@@ -250,7 +208,7 @@ You should find that the included `ruby` version is `3.1.0` as expected.
   "components": [
     {
       "type": "library",
-      "name": "ruby",
+      "name": "node-js",
       "version": "3.1.0"
     },
 ...
@@ -264,7 +222,7 @@ Congratulations! You’ve created your first configurable Cloud Native Buildpack
 
 Now that you've finished your buildpack, how about extending it? Try:
 
-- Caching the downloaded Ruby version
+- Caching the downloaded NodeJS version
 - [Packaging your buildpack for distribution][package-a-buildpack]
 
 [package-a-buildpack]: /docs/buildpack-author-guide/package-a-buildpack/