Make combine_pdf dependency optional + support Yarn PnP (#266)

Gemfile

@@ -6,6 +6,7 @@ source 'https://rubygems.org'
 gemspec
 
 gem 'childprocess', '~> 5.0'
+gem 'combine_pdf', '~> 1.0'
 gem 'mini_magick', '~> 4.12'
 gem 'pdf-reader', '~> 2.11'
 gem 'puma', '~> 6.4'

README.md

@@ -299,6 +299,16 @@ Grover.configure do |config|
 end
 ```
 
+#### Yarn PnP strategy
+
+If you are using the Yarn PnP strategy, you can override the run JS runtime for grover:
+
+```ruby
+Grover.configure do |config|
+  config.js_runtime_bin = ['yarn', 'node']
+end
+```
+
 ## Middleware
 Grover comes with a middleware that allows users to get a PDF, PNG or JPEG view of
 any page on your site by appending .pdf, .png or .jpeg/.jpg to the URL.
@@ -324,7 +334,7 @@ To enable them, there are configuration options for each image type as well as a
 
 If either of the image handling middleware options are enabled, the [ignore_path](#ignore_path) and/or
 [ignore_request](#ignore_request) should also be configured, otherwise assets are likely to be handled
-which would likely result in 404 responses.  
+which would likely result in 404 responses.
 
 ```ruby
 # config/initializers/grover.rb
@@ -401,7 +411,7 @@ end
 ```
 
 ### allow_file_uris
-The `allow_file_uris` option can be used to render an html document from the file system. 
+The `allow_file_uris` option can be used to render an html document from the file system.
 This should be used with *EXTREME CAUTION*. If used improperly it could potentially be manipulated to reveal
 sensitive files on the system. Do not enable if rendering content from outside entities
 (user uploads, external URLs, etc).
@@ -438,6 +448,8 @@ You can specify relative paths to the cover page contents using the `front_cover
 options either via the global configuration, or via meta tags. These paths (with query parameters) are then
 requested from the downstream app.
 
+Note, to use this functionality you need to add the [combine_pdf](https://rubygems.org/gems/combine_pdf) gem to your app.
+
 The cover pages are converted to PDF in isolation, and then combined together with the original PDF response,
 before being returned back up through the Rack stack.
 
@@ -559,7 +571,7 @@ The middleware and HTML preprocessing components were used heavily in the implem
 
 Thanks are also given to the excellent [Schmooze project](https://github.com/Shopify/schmooze).
 The Ruby to NodeJS interface in Grover is heavily based off that work. Grover previously used that gem,
-however migrated away due to differing requirements over persistence/cleanup of the NodeJS worker process.  
+however migrated away due to differing requirements over persistence/cleanup of the NodeJS worker process.
 
 ## License
 

grover.gemspec

@@ -29,6 +29,5 @@ Gem::Specification.new do |spec|
   spec.executables   = spec.files.grep(%r{^bin/}) { |f| File.basename(f) }
   spec.require_paths = ['lib']
 
-  spec.add_dependency 'combine_pdf', '~> 1.0'
-  spec.add_dependency 'nokogiri', '~> 1.0'
+  spec.add_dependency 'nokogiri', '~> 1'
 end

lib/grover/configuration.rb

@@ -7,9 +7,10 @@ class Grover
   class Configuration
     attr_accessor :options, :meta_tag_prefix, :ignore_path, :ignore_request,
                   :root_url, :use_pdf_middleware, :use_png_middleware,
-                  :use_jpeg_middleware, :node_env_vars, :allow_file_uris
+                  :use_jpeg_middleware, :js_runtime_bin,
+                  :node_env_vars, :allow_file_uris
 
-    def initialize
+    def initialize # rubocop:disable Metrics/MethodLength
       @options = {}
       @meta_tag_prefix = 'grover-'
       @ignore_path = nil
@@ -18,6 +19,7 @@ def initialize
       @use_pdf_middleware = true
       @use_png_middleware = false
       @use_jpeg_middleware = false
+      @js_runtime_bin = ['node']
       @node_env_vars = {}
       @allow_file_uris = false
     end

lib/grover/middleware.rb

@@ -1,7 +1,5 @@
 # frozen_string_literal: true
 
-require 'combine_pdf'
-
 class Grover
   #
   # Rack middleware for catching PDF requests and returning the upstream HTML as a PDF
@@ -132,12 +130,19 @@ def create_grover_for_response(response) # rubocop:disable Metrics/AbcSize
     end
 
     def add_cover_content(grover)
+      load_combine_pdf
       pdf = CombinePDF.parse grover.to_pdf
       pdf >> fetch_cover_pdf(grover.front_cover_path) if grover.show_front_cover?
       pdf << fetch_cover_pdf(grover.back_cover_path) if grover.show_back_cover?
       pdf.to_pdf
     end
 
+    def load_combine_pdf
+      require 'combine_pdf'
+    rescue ::LoadError
+      raise Grover::Error, 'Please add/install the "combine_pdf" gem to use the front/back cover page feature'
+    end
+
     def fetch_cover_pdf(path)
       temp_env = env.deep_dup
       scrub_env! temp_env

lib/grover/processor.rb

@@ -33,7 +33,7 @@ def convert(method, url_or_html, options)
     def spawn_process
       @stdin, @stdout, @stderr, @wait_thr = Open3.popen3(
         Grover.configuration.node_env_vars,
-        'node',
+        *Grover.configuration.js_runtime_bin,
         File.expand_path(File.join(__dir__, 'js/processor.cjs')),
         chdir: app_root
       )