Make it possible to get command help by typing 'rabbitmqctl mycommand --help'

Add a new default switch `help`
Add an alias `?`

Make rabbitmqctl display command help if this option is true for known commands.

deps/rabbitmq_cli/lib/rabbitmq/cli/core/parser.ex

@@ -218,7 +218,8 @@ defmodule RabbitMQ.CLI.Core.Parser do
       plugins_dir: :string,
       enabled_plugins_file: :string,
       aliases_file: :string,
-      erlang_cookie: :atom
+      erlang_cookie: :atom,
+      help: :boolean
     ]
   end
 
@@ -231,7 +232,8 @@ defmodule RabbitMQ.CLI.Core.Parser do
       l: :longnames,
       # for backwards compatibility,
       # not all commands support timeouts
-      t: :timeout
+      t: :timeout,
+      "?": :help
     ]
   end
 

deps/rabbitmq_cli/lib/rabbitmq/cli/ctl/commands/help_command.ex

@@ -36,12 +36,7 @@ defmodule RabbitMQ.CLI.Ctl.Commands.HelpCommand do
         all_usage(opts)
 
       command ->
-        Enum.join(
-          [base_usage(command, opts)] ++
-            options_usage() ++
-            additional_usage(command),
-          "\n\n"
-        )
+        all_usage(command, opts)
     end
   end
 
@@ -72,6 +67,13 @@ defmodule RabbitMQ.CLI.Ctl.Commands.HelpCommand do
     )
   end
 
+  def all_usage(command, opts) do
+    Enum.join([base_usage(command, opts)] ++
+              options_usage() ++
+              additional_usage(command),
+              "\n\n")
+  end
+
   def usage(), do: "help (<command> | [--list-commands])"
 
   defp tool_usage(tool_name) do

deps/rabbitmq_cli/lib/rabbitmqctl.ex

@@ -80,38 +80,44 @@ defmodule RabbitMQCtl do
 
       _ ->
         options = parsed_options |> merge_all_defaults |> normalise_options
-        {arguments, options} = command.merge_defaults(arguments, options)
 
-        maybe_with_distribution(command, options, fn ->
-          # rabbitmq/rabbitmq-cli#278
-          options = Helpers.normalise_node_option(options)
+        case options[:help] do
+          true ->
+            {:error, ExitCodes.exit_ok(), HelpCommand.all_usage(command, options)};
+          _ ->
+            {arguments, options} = command.merge_defaults(arguments, options)
 
-          # The code below implements a tiny decision tree that has
-          # to do with CLI argument and environment state validation.
+            maybe_with_distribution(command, options, fn ->
+              # rabbitmq/rabbitmq-cli#278
+              options = Helpers.normalise_node_option(options)
 
-          # validate CLI arguments
-          case command.validate(arguments, options) do
-            :ok ->
-              # then optionally validate execution environment
-              case maybe_validate_execution_environment(command, arguments, options) do
+              # The code below implements a tiny decision tree that has
+              # to do with CLI argument and environment state validation.
+
+              # validate CLI arguments
+              case command.validate(arguments, options) do
                 :ok ->
-                  result = proceed_to_execution(command, arguments, options)
-                  handle_command_output(result, command, options, output_fun)
+                  # then optionally validate execution environment
+                  case maybe_validate_execution_environment(command, arguments, options) do
+                    :ok ->
+                      result = proceed_to_execution(command, arguments, options)
+                      handle_command_output(result, command, options, output_fun)
+
+                    {:validation_failure, err} ->
+                      environment_validation_error_output(err, command, unparsed_command, options)
+
+                    {:error, _} = err ->
+                      format_error(err, options, command)
+                  end
 
                 {:validation_failure, err} ->
-                  environment_validation_error_output(err, command, unparsed_command, options)
+                  argument_validation_error_output(err, command, unparsed_command, options)
 
                 {:error, _} = err ->
                   format_error(err, options, command)
               end
-
-            {:validation_failure, err} ->
-              argument_validation_error_output(err, command, unparsed_command, options)
-
-            {:error, _} = err ->
-              format_error(err, options, command)
-          end
-        end)
+            end)
+        end
     end
   end
 

deps/rabbitmq_cli/test/rabbitmqctl_test.exs

@@ -29,6 +29,15 @@ defmodule RabbitMQCtlTest do
     :ok
   end
 
+## ------------------------ --help option -------------------------------------
+
+  test "--help option prints help for command and exits normally" do
+    command = ["status", "--help"]
+    assert capture_io(fn ->
+      error_check(command, exit_ok())
+    end) =~ ~r/Usage:/
+  end
+
 ## ------------------------ Error Messages ------------------------------------
   test "print error message on a bad connection" do
     command = ["status", "-n", "sandwich@pastrami"]