support for optional gems in Gemfile (engines/ and config/customization/gems/)

1 files changed, 83 insertions, 0 deletions

diff --git a/lib/gemfile_tools.rb b/lib/gemfile_tools.rb
new file mode 100644
index 0000000..2cdc42e
--- /dev/null
+++ b/lib/gemfile_tools.rb
@@ -0,0 +1,83 @@
+#
+# Utilities for use in Gemfile, in order to support
+# enabling and disabling gems, and including custom gems
+# in the deployment.
+#
+# Dynamic code in Gemfile is incompatible with
+# `bundle install --deployment` because dynamic code might
+# produce new Gemfile.lock. For this reason, this app must
+# be deployed with `bundle install --path vendor/bundle` instead.
+#
+
+require 'yaml'
+
+#
+# custom gems are gems placed in config/customization/gems.
+# this are added at deploy time by the platform.
+# The Gemfile.lock is then rebuilt to take these into account.
+#
+def custom_gems
+  custom_gem_dir = File.expand_path('../../config/customization/gems', __FILE__)
+  Dir["#{custom_gem_dir}/*"].collect{|gem_dir|
+    resolve_gem_directory(gem_dir)
+  }.compact
+end
+
+#
+# returns an array of [engine_name, engine_path] from Rails.root/engines/* that are
+# enabled. Uses the 'engines' key from config.yml to determine if engine is enabled
+#
+def enabled_engines(environment)
+  if local_config[environment]
+    if local_config[environment][:engines]
+      local_config[environment][:engines].collect {|engine_dir|
+        full_dir_path = File.join(File.expand_path("../../engines", __FILE__), engine_dir)
+        resolve_gem_directory(full_dir_path)
+      }.compact
+    else
+      []
+    end
+  else
+    []
+  end
+end
+
+#
+# local_config can be accessed as an indifferent hash of
+# the merger of config/default.yml and config/config.yml
+#
+def local_config
+  @local_config ||= begin
+    # a quick and dirty indifferent hash (note: does not affect children):
+    empty_hash = {}
+    empty_hash.default_proc = proc{|h, k| h.key?(k.to_s) ? h[k.to_s] : nil}
+    ["defaults.yml", "config.yml"].inject(empty_hash.dup) {|config, file|
+      filepath = File.join(File.expand_path("../../config", __FILE__), file)
+      if File.exists?(filepath)
+        new_config = YAML.load_file(filepath)
+        ['development', 'test','production'].each do |env|
+          config[env] ||= empty_hash.dup
+          config[env].merge!(new_config[env])
+        end
+      end
+      config
+    }
+  end
+end
+
+#
+# return [gem_name, relative_gem_path] for gem at the specific directory
+# or nil if not actually a gem directory
+#
+def resolve_gem_directory(gem_dir)
+  if Dir.exists?(gem_dir)
+    gemspec = Dir["#{gem_dir}/*.gemspec"]
+    if gemspec.any?
+      gem_name = File.basename(gemspec.first).sub(/\.gemspec$/,'')
+      [gem_name, gem_dir]
+    end
+  else
+    puts "Warning: no gem at `#{gem_dir}`"
+    nil
+  end
+end