Do not suggest adding non-existent gems to Gemfile

While these are valid Rack Handler names, their handler name is not the
same as their gem name.

| handler | gem        |
| ------- | ---------- |
| fastcgi | fcgi       |
| lsws    | ruby-lsapi |

railties/lib/rails/commands/server/server_command.rb

@@ -94,9 +94,10 @@ module Command
     class ServerCommand < Base # :nodoc:
       include EnvironmentArgument
 
+      RACK_HANDLER_GEMS = %w(cgi webrick scgi thin puma unicorn falcon)
       # Hard-coding a bunch of handlers here as we don't have a public way of
       # querying them from the Rack::Handler registry.
-      RACK_SERVERS = %w(cgi fastcgi webrick lsws scgi thin puma unicorn falcon)
+      RACK_HANDLERS = RACK_HANDLER_GEMS + %w(fastcgi lsws)
       RECOMMENDED_SERVER = "puma"
 
       DEFAULT_PORT = 3000
@@ -259,7 +260,7 @@ def rack_server_suggestion(server)
 
               Run `#{executable} --help` for more options.
             MSG
-          elsif server.in?(RACK_SERVERS)
+          elsif server.in?(RACK_HANDLER_GEMS)
             <<~MSG
               Could not load server "#{server}". Maybe you need to the add it to the Gemfile?
 
@@ -268,7 +269,7 @@ def rack_server_suggestion(server)
               Run `#{executable} --help` for more options.
             MSG
           else
-            error = CorrectableNameError.new("Could not find server '#{server}'.", server, RACK_SERVERS)
+            error = CorrectableNameError.new("Could not find server '#{server}'.", server, RACK_HANDLERS)
             <<~MSG
               #{error.detailed_message}
               Run `#{executable} --help` for more options.

railties/test/commands/server_test.rb

@@ -50,6 +50,18 @@ def test_using_known_server_that_isnt_in_the_gemfile
     assert_match(/Could not load server "unicorn". Maybe you need to the add it to the Gemfile/, run_command("-u", "unicorn"))
   end
 
+  def test_gem_not_suggested_when_name_not_same_as_handler
+    build_app
+
+    ["fastcgi", "lsws"].each do |server|
+      output = rails "server", "-u", server
+      assert_match(/Could not find server '#{server}'./, output)
+      assert_no_match("Gemfile", output)
+    end
+  ensure
+    teardown_app
+  end
+
   def test_daemon_with_option
     args = ["-d"]
     options = parse_arguments(args)