Auto merge of #5298 - bundler:seg-cli-gem-override, r=indirect

[CLI] Dont override Kernel#gem for bundle gem

Should fix #5296

Since `Kernel#require` calls into `Kernel#gem` as an instance method on `self`, overriding the `gem` method can lead to bad things happening

(cherry picked from commit 5135469)

lib/bundler/cli.rb

@@ -401,6 +401,8 @@ def viz
       Viz.new(options.dup).run
     end
 
+    old_gem = instance_method(:gem)
+
     desc "gem GEM [OPTIONS]", "Creates a skeleton for creating a rubygem"
     method_option :exe, :type => :boolean, :default => false, :aliases => ["--bin", "-b"], :desc => "Generate a binary executable for your library."
     method_option :coc, :type => :boolean, :desc => "Generate a code of conduct file. Set a default with `bundle config gem.coc true`."
@@ -412,10 +414,30 @@ def viz
     method_option :test, :type => :string, :lazy_default => "rspec", :aliases => "-t", :banner => "rspec",
                          :desc => "Generate a test directory for your library, either rspec or minitest. Set a default with `bundle config gem.test rspec`."
     def gem(name)
-      require "bundler/cli/gem"
-      Gem.new(options, name, self).run
     end
 
+    commands["gem"].tap do |gem_command|
+      def gem_command.run(instance, args = [])
+        arity = 1 # name
+
+        require "bundler/cli/gem"
+        cmd_args = args + [instance]
+        cmd_args.unshift(instance.options)
+
+        cmd = begin
+          Gem.new(*cmd_args)
+        rescue ArgumentError => e
+          instance.class.handle_argument_error(self, e, args, arity)
+        end
+
+        cmd.run
+      end
+    end
+
+    undef_method(:gem)
+    define_method(:gem, old_gem)
+    private :gem
+
     def self.source_root
       File.expand_path(File.join(File.dirname(__FILE__), "templates"))
     end

spec/commands/newgem_spec.rb

@@ -748,6 +748,14 @@ def create_temporary_dir(dir)
       bundle "gem 'foo bar'"
       expect(out).to end_with("Invalid gem name foo bar -- `Foo bar` is an invalid constant name")
     end
+
+    it "fails gracefully when multiple names are passed" do
+      bundle "gem foo bar baz"
+      expect(out).to eq(<<-E.strip)
+ERROR: "bundle gem" was called with arguments ["foo", "bar", "baz"]
+Usage: "bundle gem GEM [OPTIONS]"
+      E
+    end
   end
 
   describe "#ensure_safe_gem_name" do