demo: update to use interfaces directly

This adds a group and saves some lines.

demo/demo.zig

@@ -113,17 +113,16 @@ pub fn main() !u8 {
     defer _ = gpa.deinit();
     const allocator = gpa.allocator();
 
-    var parser = try cli.createParser(cliHandler, allocator);
-    defer parser.deinitTree();
+    const base = try noclip.commandGroup(allocator, .{ .description = "base group" });
+    defer base.deinitTree();
 
     var context: u32 = 2;
     const sc: []const u8 = "whassup";
 
-    var subcon = try subcommand.createParser(subHandler, allocator);
-    try parser.addSubcommand("verb", subcon.interface(&sc));
+    try base.addSubcommand("main", try cli.createInterface(allocator, cliHandler, &context));
+    try base.addSubcommand("other", try subcommand.createInterface(allocator, subHandler, &sc));
 
-    const iface = parser.interface(&context);
-    iface.execute() catch return 1;
+    try base.execute();
 
     return 0;
 }

source/command.zig

@@ -72,6 +72,76 @@ fn BuilderGenerics(comptime UserContext: type) type {
     };
 }
 
+pub const GroupOptions = struct {
+    help_flag: ShortLongPair = .{ .short_tag = "-h", .long_tag = "--help" },
+    description: []const u8,
+};
+
+pub fn commandGroup(allocator: std.mem.Allocator, comptime options: GroupOptions) !ParserInterface {
+    const cmd = comptime CommandBuilder(void){
+        .help_flag = options.help_flag,
+        .description = options.description,
+        .subcommand_required = true,
+    };
+
+    return try cmd.createInterface(allocator, cmd.noopCallback());
+}
+
+fn InterfaceCreator(comptime Command: type) type {
+    return if (Command.ICC.InputType()) |Type|
+        struct {
+            pub fn createInterface(
+                comptime self: Command,
+                allocator: std.mem.Allocator,
+                comptime callback: self.CallbackSignature(),
+                context: Type,
+            ) !ParserInterface {
+                return try self._createInterfaceImpl(allocator, callback, context);
+            }
+        }
+    else
+        struct {
+            pub fn createInterface(
+                comptime self: Command,
+                allocator: std.mem.Allocator,
+                comptime callback: self.CallbackSignature(),
+            ) !ParserInterface {
+                return try self._createInterfaceImpl(allocator, callback, void{});
+            }
+        };
+}
+
+pub const InterfaceContextCategory = union(enum) {
+    empty,
+    pointer: type,
+    value: type,
+
+    pub fn fromType(comptime ContextType: type) InterfaceContextCategory {
+        return switch (@typeInfo(ContextType)) {
+            .Void => .empty,
+            .Pointer => |info| if (info.size == .Slice) .{ .value = ContextType } else .{ .pointer = ContextType },
+            // technically, i0, u0, and struct{} should be treated as empty, probably
+            else => .{ .value = ContextType },
+        };
+    }
+
+    pub fn InputType(comptime self: InterfaceContextCategory) ?type {
+        return switch (self) {
+            .empty => null,
+            .pointer => |Type| Type,
+            .value => |Type| *const Type,
+        };
+    }
+
+    pub fn OutputType(comptime self: InterfaceContextCategory) type {
+        return switch (self) {
+            .empty => void,
+            .pointer => |Type| Type,
+            .value => |Type| Type,
+        };
+    }
+};
+
 pub fn CommandBuilder(comptime UserContext: type) type {
     return struct {
         param_spec: ncmeta.TupleBuilder = .{},
@@ -82,6 +152,7 @@ pub fn CommandBuilder(comptime UserContext: type) type {
         description: []const u8,
 
         pub const UserContextType = UserContext;
+        pub const ICC: InterfaceContextCategory = InterfaceContextCategory.fromType(UserContextType);
 
         pub fn createParser(
             comptime self: @This(),
@@ -101,11 +172,13 @@ pub fn CommandBuilder(comptime UserContext: type) type {
             };
         }
 
-        pub fn createInterface(
+        pub usingnamespace InterfaceCreator(@This());
+
+        fn _createInterfaceImpl(
             comptime self: @This(),
-            comptime callback: self.CallbackSignature(),
             allocator: std.mem.Allocator,
-            context: UserContextType,
+            comptime callback: self.CallbackSignature(),
+            context: (ICC.InputType() orelse void),
         ) !ParserInterface {
             var arena = try allocator.create(std.heap.ArenaAllocator);
             arena.* = std.heap.ArenaAllocator.init(allocator);
@@ -119,7 +192,7 @@ pub fn CommandBuilder(comptime UserContext: type) type {
                 .help_builder = help.HelpBuilder(self).init(arena_alloc),
             };
 
-            if (UserContextType == void) {
+            if (comptime ICC == .empty) {
                 return this_parser.interface();
             } else {
                 return this_parser.interface(context);
@@ -271,8 +344,14 @@ pub fn CommandBuilder(comptime UserContext: type) type {
             return self.param_spec.realTuple();
         }
 
+        pub fn noopCallback(comptime self: @This()) self.CallbackSignature() {
+            return struct {
+                fn callback(_: UserContextType, _: self.Output()) !void {}
+            }.callback;
+        }
+
         pub fn CallbackSignature(comptime self: @This()) type {
-            return *const fn (UserContext, self.Output()) anyerror!void;
+            return *const fn (UserContextType, self.Output()) anyerror!void;
         }
 
         pub fn Output(comptime self: @This()) type {

source/help.zig

@@ -53,6 +53,8 @@ pub fn StructuredPrinter(comptime Writer: type) type {
             // TODO: lol return a real error
             if (indent >= self.wrap_width) return NoclipError.UnexpectedFailure;
 
+            if (text.len == 0) return;
+
             // this assumes output stream has already had the first line properly
             // indented.
             var splitter = std.mem.split(u8, text, "\n");
@@ -227,8 +229,6 @@ pub fn HelpBuilder(comptime command: anytype) type {
 
             var just: usize = 0;
             inline for (comptime help_info.arguments) |arg| {
-                if (comptime arg.description.len == 0) continue;
-
                 const pair: AlignablePair = .{
                     .left = arg.name,
                     .right = arg.description,

source/parser.zig

@@ -99,7 +99,7 @@ pub fn Parser(comptime command: anytype, comptime callback: anytype) type {
 
         // This is a slightly annoying hack to work around the fact that there's no way
         // to provide a method signature conditionally.
-        pub usingnamespace InterfaceGen(@This(), UserContext);
+        pub usingnamespace InterfaceGen(@This(), @TypeOf(command).ICC);
         // This is attached to the struct this way because these are all "private"
         // methods that exist exclusively to cast the type-erased interface object back
         // into something usable. Their implementations aren't meaningful and just
@@ -536,32 +536,35 @@ fn InterfaceWrappers(comptime ParserType: type) type {
     };
 }
 
-fn InterfaceGen(comptime ParserType: type, comptime UserContext: type) type {
-    const CtxInfo = @typeInfo(UserContext);
+// TODO: figure out a better way of consolidating this logic with that in command.zig?
+fn InterfaceGen(comptime ParserType: type, comptime ICC: anytype) type {
+    return switch (ICC) {
+        .empty => struct {
+            pub fn interface(self: *ParserType) ParserInterface {
+                return ParserInterface.create(ParserType, self, @constCast(&void{}));
+            }
 
-    return if (CtxInfo == .Void) struct {
-        pub fn interface(self: *ParserType) ParserInterface {
-            return ParserInterface.create(ParserType, self, @constCast(&void{}));
-        }
+            fn castContext(_: ParserType, _: *anyopaque) void {
+                return void{};
+            }
+        },
+        .pointer => struct {
+            pub fn interface(self: *ParserType, context: ICC.InputType().?) ParserInterface {
+                return ParserInterface.create(ParserType, self, @constCast(context));
+            }
 
-        fn castContext(_: ParserType, _: *anyopaque) void {
-            return void{};
-        }
-    } else if (CtxInfo == .Pointer and CtxInfo.Pointer.size != .Slice) struct {
-        pub fn interface(self: *ParserType, context: UserContext) ParserInterface {
-            return ParserInterface.create(ParserType, self, @constCast(context));
-        }
+            fn castContext(_: ParserType, ctx: *anyopaque) ICC.OutputType() {
+                return @ptrCast(@alignCast(ctx));
+            }
+        },
+        .value => struct {
+            pub fn interface(self: *ParserType, context: ICC.InputType().?) ParserInterface {
+                return ParserInterface.create(ParserType, self, @ptrCast(@constCast(context)));
+            }
 
-        fn castContext(_: ParserType, ctx: *anyopaque) UserContext {
-            return @ptrCast(@alignCast(ctx));
-        }
-    } else struct {
-        pub fn interface(self: *ParserType, context: *const UserContext) ParserInterface {
-            return ParserInterface.create(ParserType, self, @ptrCast(@constCast(context)));
-        }
-
-        fn castContext(_: ParserType, ctx: *anyopaque) UserContext {
-            return @as(*const UserContext, @ptrCast(@alignCast(ctx))).*;
-        }
+            fn castContext(_: ParserType, ctx: *anyopaque) ICC.OutputType() {
+                return @as(ICC.InputType().?, @ptrCast(@alignCast(ctx))).*;
+            }
+        },
     };
 }