Detailed error message in memory threshold validation

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

@@ -40,7 +40,12 @@ defmodule RabbitMQ.CLI.Ctl.Commands.SetVmMemoryHighWatermarkCommand do
       {_, rest} ->
         case Enum.member?(Helpers.memory_units, rest) do
           true -> :ok
-          false -> {:validation_failure, :bad_argument}
+          false -> case Float.parse(arg) do
+                     {_, orest} when orest == rest ->
+                       {:validation_failure, {:bad_argument, "Invalid units."}}
+                     _ ->
+                       {:validation_failure, {:bad_argument, "The threshold should be an integer."}}
+                   end
         end
     end
   end
@@ -50,12 +55,12 @@ defmodule RabbitMQ.CLI.Ctl.Commands.SetVmMemoryHighWatermarkCommand do
   end
 
   def validate([arg], _) when is_number(arg) and (arg < 0.0 or arg > 1.0) do
-    {:validation_failure, :bad_argument}
+    {:validation_failure, {:bad_argument, "The threshold should be a fraction between 0.0 and 1.0"}}
   end
   def validate([arg], %{}) when is_binary(arg) do
     case Float.parse(arg) do
       {arg, ""} when is_number(arg) and (arg < 0.0 or arg > 1.0) ->
-               {:validation_failure, :bad_argument}
+               {:validation_failure, {:bad_argument, "The threshold should be a fraction between 0.0 and 1.0"}}
       {_, ""}   ->  :ok
       _           ->  {:validation_failure, :bad_argument}
     end

deps/rabbitmq_cli/test/set_vm_memory_high_watermark_command_test.exs

@@ -65,11 +65,15 @@ defmodule SetVmMemoryHighWatermarkCommandTest do
   end
 
   test "validate: a negative number returns a bad argument", context do
-    assert @command.validate(["-0.1"], context[:opts]) == {:validation_failure, :bad_argument}
+    assert @command.validate(["-0.1"], context[:opts]) == {:validation_failure, {:bad_argument, "The threshold should be a fraction between 0.0 and 1.0"}}
+  end
+
+  test "validate: a percentage returns a bad argument", context do
+    assert @command.validate(["40"], context[:opts]) == {:validation_failure, {:bad_argument, "The threshold should be a fraction between 0.0 and 1.0"}}
   end
 
   test "validate: a value greater than 1.0 returns a bad argument", context do
-    assert @command.validate(["1.1"], context[:opts]) == {:validation_failure, :bad_argument}
+    assert @command.validate(["1.1"], context[:opts]) == {:validation_failure, {:bad_argument, "The threshold should be a fraction between 0.0 and 1.0"}}
   end
 
   test "run: on an invalid node, return a bad rpc" do
@@ -100,7 +104,15 @@ defmodule SetVmMemoryHighWatermarkCommandTest do
   end
 
   test "validate: a single absolute integer with an invalid memory unit fails ", context do
-    assert @command.validate(["absolute","10bytes"], context[:opts]) == {:validation_failure, :bad_argument}
+    assert @command.validate(["absolute","10bytes"], context[:opts]) == {:validation_failure, {:bad_argument, "Invalid units."}}
+  end
+
+  test "validate: a single absolute float with a valid memory unit fails ", context do
+    assert @command.validate(["absolute","10.0MB"], context[:opts]) == {:validation_failure, {:bad_argument, "The threshold should be an integer."}}
+  end
+
+  test "validate: a single absolute float with an invalid memory unit fails ", context do
+    assert @command.validate(["absolute","10.0bytes"], context[:opts]) == {:validation_failure, {:bad_argument, "The threshold should be an integer."}}
   end
 
   test "validate: a single absolute string fails ", context do