Apply default options for a CLI parent command when a sub command is parsed

.release-notes/4593.md

@@ -0,0 +1,3 @@
+## Apply default options for a CLI parent command when a sub command is parsed
+
+In the CLI package's parser, a default option for a parent command was ignored when a subcommand was present. This fix makes sure that parents' defaults are applied before handling the sub command.

packages/cli/_test.pony

@@ -10,6 +10,7 @@ actor \nodoc\ Main is TestList
     test(_TestBools)
     test(_TestChat)
     test(_TestDefaults)
+    test(_TestDefaultWithSub)
     test(_TestDuplicate)
     test(_TestEnvs)
     test(_TestHelp)
@@ -238,6 +239,17 @@ class \nodoc\ iso _TestDefaults is UnitTest
     h.assert_eq[F64](42.0, cmd.option("floato").f64())
     h.assert_eq[USize](0, cmd.option("stringso").string_seq().size())
 
+class \nodoc\ iso _TestDefaultWithSub is UnitTest
+  fun name(): String => "cli/default_with_sub"
+
+  fun apply(h: TestHelper) ? =>
+    let cs = _Fixtures.default_with_sub_spec()?
+    h.assert_true(cs.is_parent())
+
+    let cmd = CommandParser(cs).parse([ "cmd"; "sub" ]) as Command
+
+    h.assert_eq[String]("foo", cmd.option("arg").string())
+
 class \nodoc\ iso _TestShortsAdj is UnitTest
   fun name(): String => "cli/shorts_adjacent"
 
@@ -668,3 +680,14 @@ primitive _Fixtures
           ArgSpec.string_seq("args", "Arguments to run.")
         ])?
     ])?
+
+  fun default_with_sub_spec(): CommandSpec box ? =>
+    let root = CommandSpec.parent(
+      "cmd",
+      "Main command",
+      [ OptionSpec.string("arg", "an arg" where default' = "foo") ])?
+    let sub = CommandSpec.leaf("sub", "Sub command")?
+
+    root.add_command(sub)?
+    root.add_help()?
+    root

packages/cli/command_parser.pony

@@ -98,6 +98,12 @@ class CommandParser
           try
             match _spec.commands()(token)?
             | let cs: CommandSpec box =>
+              // check args and assign defaults
+              match _check_args(options, args, envsmap, arg_pos)
+              | let se: SyntaxError =>
+                return se
+              end
+
               return CommandParser._sub(cs, this).
                 _parse_command(tokens, options, args, envsmap, opt_stop)
             end
@@ -143,6 +149,29 @@ class CommandParser
       return Help.general(_root_spec())
     end
 
+    // check args and assign defaults
+    match _check_args(options, args, envsmap, arg_pos)
+    | let se: SyntaxError =>
+      return se
+    end
+
+    // Specifying only the parent and not a leaf command is an error.
+    if _spec.is_parent() then
+      return SyntaxError(_spec.name(), "missing subcommand")
+    end
+
+    // A successfully parsed and populated leaf Command.
+    Command._create(_spec, _fullname(), consume options, args)
+
+  fun _check_args(
+    options: Map[String,Option] ref,
+    args: Map[String,Arg] ref,
+    envsmap: Map[String, String] box,
+    arg_pos': USize)
+    : (SyntaxError | USize)
+  =>
+    var arg_pos = arg_pos'
+
     // Fill in option values from env or from coded defaults.
     for os in _spec.options().values() do
       if not options.contains(os.name()) then
@@ -190,14 +219,7 @@ class CommandParser
       end
       arg_pos = arg_pos + 1
     end
-
-    // Specifying only the parent and not a leaf command is an error.
-    if _spec.is_parent() then
-      return SyntaxError(_spec.name(), "missing subcommand")
-    end
-
-    // A successfully parsed and populated leaf Command.
-    Command._create(_spec, _fullname(), consume options, args)
+    arg_pos
 
   fun _parse_long_option(
     token: String,