Engine Discovery

LesliSystem discovers loaded Rails engines from its known engine registry and adds metadata for the host application.

List Engines

engines = LesliSystem.engines

The result is keyed by Ruby namespace:

engines.each do |name, metadata|
  puts "#{name}: #{metadata[:version]} at #{metadata[:path]}"
end

Only known engine constants that are loaded when the registry is built are included. The synthetic Root entry is always present:

LesliSystem.engines.fetch("Root")
# {
#   code: "root",
#   name: "Root",
#   path: "/",
#   version: "1.0.0",
#   summary: "",
#   description: "",
#   metadata: [],
#   build: "0000000",
#   dir: Rails.root.to_s
# }

Find One Engine

Pass a string or symbol to LesliSystem.engine:

LesliSystem.engine("LesliSupport")
LesliSystem.engine(:lesli_support)

Names are converted with Active Support's camelize, so both examples resolve the LesliSupport registry entry.

Pass a second argument to return one property:

LesliSystem.engine("LesliSupport", :path)
LesliSystem.engine("LesliSupport", "version")

The property may be a string or symbol. An unknown property returns nil when the engine exists.

Missing Engines

A name that is not in LesliSystem's known engine list resolves to the synthetic Root entry:

LesliSystem.engine("CustomApplication") == LesliSystem.engine("Root")
# true

A known engine whose constant was not loaded is absent from the registry. Requesting its complete metadata returns nil; requesting a property directly is not safe in that case. Check the complete result first:

engine = LesliSystem.engine("LesliCalendar")
path = engine[:path] if engine

Mounted Paths

For each loaded engine, LesliSystem asks its Rails engine routes for the current script name. The resulting path reflects the mount known when the registry is first built.

Because the registry is memoized, load and mount engines before the first call. Restart the process after changing routes or installed engines.