Implemented Empty Option handling

- Added `allow_empty` to Options, enabling any Option to be passed without an associated Value regardless of the Value's Child Type.
- Updated `cova.parse` and `Value` to properly handle the new Empty state.
- Closed #64.

examples/covademo.zig

@@ -403,6 +403,7 @@ pub const setup_cmd: CommandT = .{
             .short_name = 's',
             .long_name = "string",
             .alias_long_names = &.{ "text" },
+            .allow_empty = true,
             .val = ValueT.ofType([]const u8, .{
                 .name = "string_val",
                 .description = "A string value.",
@@ -627,7 +628,11 @@ pub fn main() !void {
         }
     );
     var main_opts = try main_cmd.getOpts(.{});
-    if (main_opts.get("string_opt")) |str_opt| {
+    if (main_opts.get("string_opt")) |str_opt| strOpt: {
+        if (str_opt.val.isEmpty()) {
+            log.debug("This Option was set, but intentionally left empty.", .{});
+            break :strOpt;
+        }
         const opt_strs = try str_opt.val.getAllAs([]const u8);
         log.debug("Option Strings (--string): {d}", .{ opt_strs.len });
         for (opt_strs, 0..) |str, idx| log.debug(" {d}. {s}", .{ idx, str });

src/Option.zig

@@ -227,7 +227,7 @@ pub fn Custom(comptime config: Config) type {
         name: []const u8,
         /// The Description of this Option for Usage/Help messages.
         description: []const u8 = "",
-        /// Hide thie Command from Usage/Help messages.
+        /// Hide this Command from Usage/Help messages.
         hidden: bool = false,
 
         /// During parsing, mandate that THIS Option must be used in a case-sensitive manner when called by its Long Name.
@@ -236,6 +236,8 @@ pub fn Custom(comptime config: Config) type {
         /// During parsing, mandate that this Option is given.
         /// This will do nothing if this Option's Value has a default value.
         mandatory: bool = false,
+        /// Allow this Option's Value to Empty even if it's not a Boolean.
+        allow_empty: bool = false,
 
         // (WIP) TODO: Figure out if this is possible
         ///// A custom Help function to override the default `help()` function for this custom Option INSTANCE.

src/Value.zig

@@ -218,14 +218,14 @@ pub fn Typed(comptime SetT: type, comptime config: Config) type {
         ///
         /// **Internal Use.**
         _entry_idx: u7 = 0,
-        /// The Max number of Raw Argument Entries that can be provided.
+        /// The Max number of Raw Argument Entries that can be provided. 
         /// This must be between 1 to the value of `config.max_children`.
         max_entries: u7 = 1,
         /// Flag to determine if this Value is at max capacity for Raw Arguments.
         ///
         /// *This should be Read-Only for library users.*
         is_maxed: bool = false,
-        /// Delimiter Characters that can be used to split up Multi-Values or Multi-Options.
+        /// Delimiter Characters that can be used to split up Multi-Values or Multi-Options. 
         /// This is only applicable if `set_behavior = .Multi`.
         arg_delims: []const u8 = config.global_arg_delims,
         /// Set Behavior for this Value.
@@ -236,6 +236,11 @@ pub fn Typed(comptime SetT: type, comptime config: Config) type {
         ///
         /// *This should be Read-Only for library users.*
         is_set: bool = false,
+        /// Flag to determine if this Value has been set to Empty. 
+        /// This is intended to be used w/ Options.
+        ///
+        /// *This should be Read-Only for library users.*
+        is_empty: bool = true,
 
         /// A Parsing Function to be used in place of the normal `parse()` for Argument Parsing for this specific Value.
         /// This will be used FIRST, before `type_parse_fn` then the normal `parse()` functions are tried.
@@ -336,10 +341,19 @@ pub fn Typed(comptime SetT: type, comptime config: Config) type {
                     }
                 }
                 @constCast(self).is_maxed = self._entry_idx == self.max_entries;
+                @constCast(self).is_empty = false;
             }
             else return error.InvalidValue;
         }
 
+        /// Set this Value without actual data so that it's "empty". 
+        /// This is intended to be used with Options.
+        pub fn setEmpty(self: *const @This()) !void {
+            if (!self.is_empty) return error.NotEmpty;
+            if (@constCast(self).default_val) |_| @constCast(self).default_val = null;
+            @constCast(self).is_set = true;
+        }
+
         /// Get the first Parsed and Validated value of this Value.
         /// This will pull the first value from `_set_args` and should be used with the `First` or `Last` Set Behaviors.
         pub fn get(self: *const @This()) !ChildT {
@@ -682,6 +696,13 @@ pub fn Custom(comptime config: Config) type {
                 inline else => |tag| try @field(self.*.generic, @tagName(tag)).set(arg),
             }
         }
+        /// Set the inner Typed Value without data so that it is "empty". 
+        /// This is meant to be used with Options
+        pub fn setEmpty(self: *const @This()) !void { 
+            switch (meta.activeTag(self.*.generic)) {
+                inline else => |tag| try @field(self.*.generic, @tagName(tag)).setEmpty(),
+            }
+        }
 
         /// Set a new Argument Index for this Value.
         pub fn setArgIdx(self: *const @This(), arg_idx: u8) !void {
@@ -774,6 +795,12 @@ pub fn Custom(comptime config: Config) type {
                 inline else => |tag| @field(self.*.generic, @tagName(tag)).is_set,
             };
         }
+        /// Check if the inner Typed Value is Empty.
+        pub fn isEmpty(self: *const @This()) bool {
+            return switch (meta.activeTag(self.*.generic)) {
+                inline else => |tag| @field(self.*.generic, @tagName(tag)).is_empty,
+            };
+        }
         /// Check if the inner Typed Value has a default value.
         pub fn hasDefault(self: *const @This()) bool {
             return switch (meta.activeTag(self.*.generic)) {

src/cova.zig

@@ -629,7 +629,16 @@ fn parseOpt(args: *ArgIteratorGeneric, comptime OptionType: type, opt: *const Op
     const peek_arg = args.peek();
     const set_arg = 
         if (peek_arg == null or peek_arg.?[0] == '-') setArg: {
-            if (!(mem.eql(u8, opt.val.childType(), "bool") and !opt.val.hasCustomParseFn())) return error.EmptyArgumentProvidedToOption;
+            if (!(mem.eql(u8, opt.val.childType(), "bool"))) {
+                if (opt.allow_empty) {
+                    opt.val.setEmpty() catch 
+                        log.err("The Option '{s}' has already been set.", .{ opt.name });
+                    _ = args.next();
+                    return;
+                }
+                else if (!opt.val.hasCustomParseFn()) 
+                    return error.EmptyArgumentProvidedToOption;
+            }
             _ = args.next();
             break :setArg "true";
         }