Fix missing optional arguments to win over values

lib/dry/cli/option.rb

@@ -124,6 +124,8 @@ def alias_names
 
       # @api private
       def valid_value?(value)
+        return true if value.nil? && !required?
+
         available_values = values
         return true if available_values.nil?
 

spec/support/fixtures/shared_commands.rb

@@ -88,6 +88,17 @@ def call(steps:, **)
         puts steps
       end
     end
+
+    class Vacuum < Dry::CLI::Command
+      desc "Vacuum the database"
+
+      argument :mode, desc: "Optional mode of vacuum", required: true, values: [:full, :freeze, :verbose]
+      argument :parallel, desc: "Parallel workers", values: [1, 2, 3]
+
+      def call(mode:, parallel: nil, **)
+        puts "mode: #{mode}, parallel: #{parallel}"
+      end
+    end
   end
 
   module Destroy

spec/support/fixtures/with_block.rb

@@ -34,14 +34,15 @@
   cli.register "callbacks",        Webpack::CLI::CallbacksCommand
 
   cli.register "db" do |prefix|
-    prefix.register "apply",   Commands::DB::Apply
-    prefix.register "console", Commands::DB::Console
-    prefix.register "create",  Commands::DB::Create
-    prefix.register "drop",    Commands::DB::Drop
-    prefix.register "migrate", Commands::DB::Migrate
-    prefix.register "prepare", Commands::DB::Prepare
-    prefix.register "version", Commands::DB::Version
+    prefix.register "apply",    Commands::DB::Apply
+    prefix.register "console",  Commands::DB::Console
+    prefix.register "create",   Commands::DB::Create
+    prefix.register "drop",     Commands::DB::Drop
+    prefix.register "migrate",  Commands::DB::Migrate
+    prefix.register "prepare",  Commands::DB::Prepare
+    prefix.register "version",  Commands::DB::Version
     prefix.register "rollback", Commands::DB::Rollback
+    prefix.register "vacuum",   Commands::DB::Vacuum
   end
 
   cli.register "destroy", aliases: ["d"] do |prefix|

spec/support/fixtures/with_registry.rb

@@ -12,14 +12,15 @@ module Commands
       register "assets precompile", ::Commands::Assets::Precompile
       register "console",           ::Commands::Console
       register "db" do |prefix|
-        prefix.register "apply",   ::Commands::DB::Apply
-        prefix.register "console", ::Commands::DB::Console
-        prefix.register "create",  ::Commands::DB::Create
-        prefix.register "drop",    ::Commands::DB::Drop
-        prefix.register "migrate", ::Commands::DB::Migrate
-        prefix.register "prepare", ::Commands::DB::Prepare
-        prefix.register "version", ::Commands::DB::Version
+        prefix.register "apply",    ::Commands::DB::Apply
+        prefix.register "console",  ::Commands::DB::Console
+        prefix.register "create",   ::Commands::DB::Create
+        prefix.register "drop",     ::Commands::DB::Drop
+        prefix.register "migrate",  ::Commands::DB::Migrate
+        prefix.register "prepare",  ::Commands::DB::Prepare
+        prefix.register "version",  ::Commands::DB::Version
         prefix.register "rollback", ::Commands::DB::Rollback
+        prefix.register "vacuum",   ::Commands::DB::Vacuum
       end
 
       register "destroy", aliases: ["d"] do |prefix|

spec/support/fixtures/with_zero_arity_block.rb

@@ -35,14 +35,15 @@
   register "callbacks",        Webpack::CLI::CallbacksCommand
 
   register "db" do
-    register "apply",   Commands::DB::Apply
-    register "console", Commands::DB::Console
-    register "create",  Commands::DB::Create
-    register "drop",    Commands::DB::Drop
-    register "migrate", Commands::DB::Migrate
-    register "prepare", Commands::DB::Prepare
-    register "version", Commands::DB::Version
+    register "apply",    Commands::DB::Apply
+    register "console",  Commands::DB::Console
+    register "create",   Commands::DB::Create
+    register "drop",     Commands::DB::Drop
+    register "migrate",  Commands::DB::Migrate
+    register "prepare",  Commands::DB::Prepare
+    register "version",  Commands::DB::Version
     register "rollback", Commands::DB::Rollback
+    register "vacuum",   Commands::DB::Vacuum
   end
 
   register "destroy", aliases: ["d"] do

spec/support/shared_examples/commands.rb

@@ -156,15 +156,15 @@
         expect(output).to eq("exec - Task: test - Directories: []\n")
       end
 
-      it "capture all the remaining arguments" do
+      it "captures all the remaining arguments" do
         output = capture_output { cli.call(arguments: %w[exec test api admin]) }
         expect(output).to eq("exec - Task: test - Directories: [\"api\", \"admin\"]\n")
       end
     end
 
     context "with supported values" do
       context "and with supported value passed" do
-        it "call the command with the option" do
+        it "calls the command with the option" do
           output = capture_output { cli.call(arguments: %w[console --engine=pry]) }
           expect(output).to eq("console - engine: pry\n")
         end
@@ -183,6 +183,20 @@
           expect(error).to eq("ERROR: \"rspec db rollback\" was called with arguments \"4\"\n")
         end
       end
+
+      context "without a required argument limited by values array" do
+        it "prints error" do
+          error = capture_error { cli.call(arguments: %w[db vacuum]) }
+          expect(error).to eq("ERROR: \"rspec db vacuum\" was called with arguments \"\"\n")
+        end
+      end
+
+      context "without an optional argument limited by values array" do
+        it "can be used" do
+          output = capture_output { cli.call(arguments: %w[db vacuum full]) }
+          expect(output).to eq("mode: full, parallel: \n")
+        end
+      end
     end
 
     it "with help param" do