Quote some values in error messages

This helps to understand the errors about invalid arguments when the
argument's value is the empty string.

Signed-off-by: Stephen Sherratt <stephen@sherra.tt>

Author: gridbugs

CHANGES.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## Unreleased
+
+### Changed
+
+- Quote some values in error messages (#24)
+
 ## 0.8.4
 
 ### Changed

src/climate/error.ml

@@ -93,20 +93,20 @@ module Parse_error = struct
        | None -> sprintf "Failed to parse the argument: %s" message)
     | Too_many_positional_arguments { max = 0; first_excess_argument } ->
       sprintf
-        "This command does not accept any positional arguments. First excess argument: %s"
+        "This command does not accept any positional arguments. First excess argument: %S"
         first_excess_argument
     | Too_many_positional_arguments { max; first_excess_argument } ->
       sprintf
         "Too many positional arguments. At most %d positional arguments may be passed. \
-         First excess argument: %s"
+         First excess argument: %S"
         max
         first_excess_argument
     | Invalid_char_in_argument_name { attempted_argument_name; invalid_char } ->
       sprintf
         "Invalid character %C in argument name %S"
         invalid_char
         attempted_argument_name
-    | No_such_subcommand subcommand -> sprintf "No such subcommand: %s" subcommand
+    | No_such_subcommand subcommand -> sprintf "No such subcommand: %S" subcommand
   ;;
 
   let exit_code = 124

tests/unit_tests/parse_error_tests.ml

@@ -12,6 +12,12 @@ let%expect_test "positional args passed to command with no positional args" =
     {| This command does not accept any positional arguments. First excess argument: foo |}]
 ;;
 
+let%expect_test "empty string passed to command with no positional args" =
+  run (Command.singleton (Arg_parser.const ())) [ "" ];
+  [%expect
+    {| This command does not accept any positional arguments. First excess argument: foo |}]
+;;
+
 let%expect_test "positional args passed to command with no positional args" =
   let term = Arg_parser.(pos_req 0 string) in
   run (Command.singleton term) [ "foo"; "bar"; "baz" ];