Unify rake task dependency checking

This prepares for task generalisation.

This also solves the semantic difference between the need for the
minitest rake task backport and the absence of minitest, which would
otherwise fail if minitest were missing.

tasks/bundler.rake

@@ -1 +1,10 @@
-require "bundler/gem_tasks"
+# frozen_string_literal: true
+
+# @type self: Rake::DSL
+
+if Gem.loaded_specs["bundler"]
+  require "bundler/gem_tasks"
+else
+  warn "'bundler' gem not loaded: skipping tasks..." if Rake.verbose == true
+  return
+end

tasks/rbs.rake

@@ -2,6 +2,13 @@
 
 # @type self: Rake::DSL
 
+if Gem.loaded_specs["rbs"]
+  # noop
+else
+  warn "'rbs' gem not loaded: skipping tasks..." if Rake.verbose == true
+  return
+end
+
 namespace :rbs do
   namespace :collection do
     desc "Install RBS signatures"

tasks/rspec.rake

@@ -2,9 +2,9 @@
 
 # @type self: Rake::DSL
 
-begin
+if Gem.loaded_specs["rspec"]
   require "rspec/core/rake_task"
-rescue LoadError
+else
   warn "'rspec' gem not loaded: skipping tasks..." if Rake.verbose == true
   return
 end

tasks/rubocop.rake

@@ -2,10 +2,10 @@
 
 # @type self: Rake::DSL
 
-begin
+if Gem.loaded_specs["rubocop"]
   require "rubocop/rake_task"
-rescue LoadError
-  warn "'rubocop' gem not loaded: skipping tasks..."
+else
+  warn "'rubocop' gem not loaded: skipping tasks..." if Rake.verbose == true
   return
 end
 

tasks/standard.rake

@@ -2,10 +2,10 @@
 
 # @type self: Rake::DSL
 
-begin
+if Gem.loaded_specs["standard"]
   require "standard/rake"
-rescue LoadError
-  warn "'standard' gem not loaded: skipping tasks..."
+else
+  warn "'standard' gem not loaded: skipping tasks..." if Rake.verbose == true
   return
 end
 

tasks/steep.rake

@@ -2,10 +2,10 @@
 
 # @type self: Rake::TaskLib
 
-begin
+if Gem.loaded_specs["steep"]
   require "steep"
-rescue LoadError
-  warn "'steep' gem not loaded: skipping tasks..."
+else
+  warn "'steep' gem not loaded: skipping tasks..." if Rake.verbose == true
   return
 end
 

tasks/test.rake

@@ -2,11 +2,16 @@
 
 # @type self: Rake::DSL
 
-begin
-  require "minitest/test_task"
-rescue LoadError
-  # Backport "minitest/test_task" for minitest 5.15.0
-  require_relative "../vendor/minitest/test_task"
+if Gem.loaded_specs["minitest"]
+  begin
+    require "minitest/test_task"
+  rescue LoadError
+    # Backport "minitest/test_task" for minitest 5.15.0
+    require_relative "../vendor/minitest/test_task"
+  end
+else
+  warn "'minitest' gem not loaded: skipping tasks..." if Rake.verbose == true
+  return
 end
 
 Minitest::TestTask.create(:test) do |t|