fix cli issue when providing --help=false.

Fixes ponylang#3439

packages/cli/_test.pony

@@ -26,6 +26,7 @@ actor Main is TestList
     test(_TestChat)
     test(_TestMustBeLeaf)
     test(_TestHelp)
+    test(_TestHelpFalse)
     test(_TestHelpMultipleArgs)
 
 class iso _TestMinimal is UnitTest
@@ -514,6 +515,28 @@ class iso _TestHelp is UnitTest
     h.log(help)
     h.assert_true(help.contains("Address of the server"))
 
+class iso _TestHelpFalse is UnitTest
+  fun name(): String => "ponycli/help-false"
+
+  fun apply(h: TestHelper) ? =>
+    let cs =
+      CommandSpec.leaf("bools", "A sample CLI with four bool options", [
+        OptionSpec.string("name" where short' = 'n', default' = "John")
+      ])?.>add_help()?
+    let args = [
+       "ignored"
+       "--help=false"
+    ]
+    let cmd = CommandParser(cs).parse(args)
+    match cmd
+    | let c: Command =>
+      h.assert_false(c.option("help").bool())
+      h.assert_eq[String]("John", c.option("name").string())
+    | let ch: CommandHelp => h.fail("--help=false is interpretet as demanding help output.")
+    | let se: SyntaxError =>
+      h.fail("--help=false is not handled correctly: " + se.string())
+    end
+
 class iso _TestHelpMultipleArgs is UnitTest
   fun name(): String => "ponycli/help-multiple-args"
 

packages/cli/command_parser.pony

@@ -120,13 +120,16 @@ class CommandParser
     end
 
     // If it's a help option, return a general or specific CommandHelp.
-    if options.contains(_help_name()) then
-      return
-        if _spec is _root_spec() then
-          Help.general(_root_spec())
-        else
-          Help.for_command(_root_spec(), [_spec.name()])
-        end
+    try
+      let help_option = options(_help_name())?
+      if help_option.bool() then
+        return
+          if _spec is _root_spec() then
+            Help.general(_root_spec())
+          else
+            Help.for_command(_root_spec(), [_spec.name()])
+          end
+      end
     end
 
     // If it's a help command, return a general or specific CommandHelp.