Validates if rbs is installed when Steepfile is loaded

Author: soutaro

lib/steep/drivers/utils/driver_helper.rb

@@ -10,6 +10,16 @@ def load_config(path: steepfile || Pathname("Steepfile"))
           steep_file_path = path.absolute? ? path : Pathname.pwd + path
           Project.new(steepfile_path: steep_file_path).tap do |project|
             Project::DSL.parse(project, path.read, filename: path.to_s)
+
+            project.targets.each do |target|
+              if collection_lock = target.options.collection_lock
+                begin
+                  collection_lock.check_rbs_availability!
+                rescue RBS::Collection::Config::CollectionNotAvailable
+                  raise "Run `rbs collection install` to install type definitions"
+                end
+              end
+            end
           end
         end
 

sig/steep/project/options.rbs

@@ -19,7 +19,7 @@ module Steep
 
       attr_accessor paths: PathOptions
 
-      attr_accessor collection_lock: RBS::Collection::Config::Lockfile
+      attr_accessor collection_lock: RBS::Collection::Config::Lockfile?
 
       def initialize: () -> void
     end