main.zig

// SPDX-FileCopyrightText: 2021 Yoran Heling <projects@yorhel.nl>
// SPDX-License-Identifier: MIT

pub const program_version = "2.0-beta2";

const std = @import("std");
const model = @import("model.zig");
const scan = @import("scan.zig");
const ui = @import("ui.zig");
const browser = @import("browser.zig");
const delete = @import("delete.zig");
const util = @import("util.zig");
const c = @cImport(@cInclude("locale.h"));

// "Custom" allocator that wraps the libc allocator and calls ui.oom() on error.
// This allocator never returns an error, it either succeeds or causes ncdu to quit.
// (Which means you'll find a lot of "catch unreachable" sprinkled through the code,
// they look scarier than they are)
fn wrapAlloc(alloc: *std.mem.Allocator, len: usize, alignment: u29, len_align: u29, return_address: usize) error{OutOfMemory}![]u8 {
    while (true) {
        if (std.heap.c_allocator.allocFn(alloc, len, alignment, len_align, return_address)) |r|
            return r
        else |_| {}
        ui.oom();
    }
}

fn wrapResize(alloc: *std.mem.Allocator, buf: []u8, buf_align: u29, new_len: usize, len_align: u29, return_address: usize) std.mem.Allocator.Error!usize {
    // AFAIK, all uses of resizeFn to grow an allocation will fall back to allocFn on failure.
    return std.heap.c_allocator.resizeFn(alloc, buf, buf_align, new_len, len_align, return_address);
}

var allocator_state = std.mem.Allocator{
    .allocFn = wrapAlloc,
    .resizeFn = wrapResize,
};
pub const allocator = &allocator_state;
//var general_purpose_allocator = std.heap.GeneralPurposeAllocator(.{}){};
//pub const allocator = &general_purpose_allocator.allocator;

pub const config = struct {
    pub const SortCol = enum { name, blocks, size, items, mtime };
    pub const SortOrder = enum { asc, desc };

    pub var same_fs: bool = false;
    pub var extended: bool = false;
    pub var follow_symlinks: bool = false;
    pub var exclude_caches: bool = false;
    pub var exclude_kernfs: bool = false;
    pub var exclude_patterns: std.ArrayList([:0]const u8) = std.ArrayList([:0]const u8).init(allocator);

    pub var update_delay: u64 = 100*std.time.ns_per_ms;
    pub var scan_ui: ?enum { none, line, full } = .full;
    pub var si: bool = false;
    pub var nc_tty: bool = false;
    pub var ui_color: enum { off, dark, darkbg } = .off;
    pub var thousands_sep: []const u8 = ",";

    pub var show_hidden: bool = true;
    pub var show_blocks: bool = true;
    pub var show_shared: enum { off, shared, unique } = .shared;
    pub var show_items: bool = false;
    pub var show_mtime: bool = false;
    pub var show_graph: bool = true;
    pub var show_percent: bool = false;
    pub var sort_col: SortCol = .blocks;
    pub var sort_order: SortOrder = .desc;
    pub var sort_dirsfirst: bool = false;

    pub var imported: bool = false;
    pub var can_delete: ?bool = true;
    pub var can_shell: ?bool = true;
    pub var can_refresh: ?bool = true;
    pub var confirm_quit: bool = false;
    pub var confirm_delete: bool = true;
    pub var ignore_delete_errors: bool = false;
};

pub var state: enum { scan, browse, refresh, shell, delete } = .scan;

// Simple generic argument parser, supports getopt_long() style arguments.
// T can be any type that has a 'fn next(T) ?[:0]const u8' method, e.g.:
//   var args = Args(std.process.ArgIteratorPosix).init(std.process.ArgIteratorPosix.init());
fn Args(T: anytype) type {
    return struct {
        it: T,
        short: ?[:0]const u8 = null, // Remainder after a short option, e.g. -x<stuff> (which may be either more short options or an argument)
        last: ?[]const u8 = null,
        last_arg: ?[:0]const u8 = null, // In the case of --option=<arg>
        shortbuf: [2]u8 = undefined,
        argsep: bool = false,

        const Self = @This();
        const Option = struct {
            opt: bool,
            val: []const u8,

            fn is(self: @This(), cmp: []const u8) bool {
                return self.opt and std.mem.eql(u8, self.val, cmp);
            }
        };

        fn init(it: T) Self {
            return Self{ .it = it };
        }

        fn shortopt(self: *Self, s: [:0]const u8) Option {
            self.shortbuf[0] = '-';
            self.shortbuf[1] = s[0];
            self.short = if (s.len > 1) s[1.. :0] else null;
            self.last = &self.shortbuf;
            return .{ .opt = true, .val = &self.shortbuf };
        }

        /// Return the next option or positional argument.
        /// 'opt' indicates whether it's an option or positional argument,
        /// 'val' will be either -x, --something or the argument.
        pub fn next(self: *Self) ?Option {
            if (self.last_arg != null) ui.die("Option '{s}' does not expect an argument.\n", .{ self.last.? });
            if (self.short) |s| return self.shortopt(s);
            const val = self.it.next() orelse return null;
            if (self.argsep or val.len == 0 or val[0] != '-') return Option{ .opt = false, .val = val };
            if (val.len == 1) ui.die("Invalid option '-'.\n", .{});
            if (val.len == 2 and val[1] == '-') {
                self.argsep = true;
                return self.next();
            }
            if (val[1] == '-') {
                if (std.mem.indexOfScalar(u8, val, '=')) |sep| {
                    if (sep == 2) ui.die("Invalid option '{s}'.\n", .{val});
                    self.last_arg = val[sep+1.. :0];
                    self.last = val[0..sep];
                    return Option{ .opt = true, .val = self.last.? };
                }
                self.last = val;
                return Option{ .opt = true, .val = val };
            }
            return self.shortopt(val[1..:0]);
        }

        /// Returns the argument given to the last returned option. Dies with an error if no argument is provided.
        pub fn arg(self: *Self) [:0]const u8 {
            if (self.short) |a| {
                defer self.short = null;
                return a;
            }
            if (self.last_arg) |a| {
                defer self.last_arg = null;
                return a;
            }
            if (self.it.next()) |o| return o;
            ui.die("Option '{s}' requires an argument.\n", .{ self.last.? });
        }
    };
}

const ArgsFile = struct {
    f: std.fs.File,
    path: []const u8,
    buf: std.io.BufferedReader(4096, std.fs.File.Reader),
    hasarg: bool = false,
    ch: u8 = 0,

    fn open(path: [:0]const u8) ?ArgsFile {
        const f = std.fs.cwd().openFileZ(path, .{}) catch |e| switch (e) {
            error.FileNotFound => return null,
            else => ui.die("Error opening {s}: {s}\n", .{ path, ui.errorString(e) }),
        };
        var self = ArgsFile{
            .f = f,
            .path = path,
            .buf = std.io.bufferedReader(f.reader()),
        };
        self.con();
        return self;
    }

    fn con(self: *ArgsFile) void {
        self.ch = self.buf.reader().readByte() catch |e| switch (e) {
            error.EndOfStream => 0,
            else => ui.die("Error reading from {s}: {s}\n", .{ self.path, ui.errorString(e) }),
        };
    }

    // Return value /should/ be freed, but the rest of the argument parsing
    // code won't bother with that. Leaking arguments isn't a big deal.
    fn next(self: *ArgsFile) ?[:0]const u8 {
        while (true) {
            while (true) {
                switch (self.ch) {
                    0 => return null,
                    '\n', ' ', '\t', '\r' => {},
                    else => break,
                }
                self.con();
            }
            if (self.ch == '#') {
                while (true) {
                    self.con();
                    if (self.ch == 0) return null;
                    if (self.ch == '\n') break;
                }
            } else break;
        }
        var val = std.ArrayList(u8).init(allocator);
        if (self.hasarg) {
            while (self.ch != '\n' and self.ch != 0) {
                val.append(self.ch) catch unreachable;
                self.con();
            }
            self.hasarg = false;
        } else {
            while (true) {
                switch (self.ch) {
                    '=', ' ', '\t', '\r' => { self.hasarg = true; break; },
                    '\n' => break,
                    0 => return null,
                    else => val.append(self.ch) catch unreachable,
                }
                self.con();
            }
        }
        return util.arrayListBufZ(&val);
    }
};

// TODO: Rewrite this (and Args(), I guess) to be non-generic, it rather bloats
// the binary this way.
fn argConfig(args: anytype, opt: anytype) bool {
    if (opt.is("-q") or opt.is("--slow-ui-updates")) config.update_delay = 2*std.time.ns_per_s
    else if (opt.is("--fast-ui-updates")) config.update_delay = 100*std.time.ns_per_ms
    else if (opt.is("-x") or opt.is("--one-file-system")) config.same_fs = true
    else if (opt.is("--cross-file-system")) config.same_fs = false
    else if (opt.is("-e") or opt.is("--extended")) config.extended = true
    else if (opt.is("--no-extended")) config.extended = false
    else if (opt.is("-r") and !(config.can_delete orelse true)) config.can_shell = false
    else if (opt.is("-r")) config.can_delete = false
    else if (opt.is("--enable-shell")) config.can_shell = true
    else if (opt.is("--disable-shell")) config.can_shell = false
    else if (opt.is("--enable-delete")) config.can_delete = true
    else if (opt.is("--disable-delete")) config.can_delete = false
    else if (opt.is("--enable-refresh")) config.can_refresh = true
    else if (opt.is("--disable-refresh")) config.can_refresh = false
    else if (opt.is("--show-hidden")) config.show_hidden = true
    else if (opt.is("--hide-hidden")) config.show_hidden = false
    else if (opt.is("--show-itemcount")) config.show_items = true
    else if (opt.is("--hide-itemcount")) config.show_items = false
    else if (opt.is("--show-mtime")) config.show_mtime = true
    else if (opt.is("--hide-mtime")) config.show_mtime = false
    else if (opt.is("--show-graph")) config.show_graph = true
    else if (opt.is("--hide-graph")) config.show_graph = false
    else if (opt.is("--show-percent")) config.show_percent = true
    else if (opt.is("--hide-percent")) config.show_percent = false
    else if (opt.is("--group-directories-first")) config.sort_dirsfirst = true
    else if (opt.is("--no-group-directories-first")) config.sort_dirsfirst = false
    else if (opt.is("--sort")) {
        var val: []const u8 = args.arg();
        var ord: ?config.SortOrder = null;
        if (std.mem.endsWith(u8, val, "-asc")) {
            val = val[0..val.len-4];
            ord = .asc;
        } else if (std.mem.endsWith(u8, val, "-desc")) {
            val = val[0..val.len-5];
            ord = .desc;
        }
        if (std.mem.eql(u8, val, "name")) {
            config.sort_col = .name;
            config.sort_order = ord orelse .asc;
        } else if (std.mem.eql(u8, val, "disk-usage")) {
            config.sort_col = .blocks;
            config.sort_order = ord orelse .desc;
        } else if (std.mem.eql(u8, val, "apparent-size")) {
            config.sort_col = .size;
            config.sort_order = ord orelse .desc;
        } else if (std.mem.eql(u8, val, "itemcount")) {
            config.sort_col = .items;
            config.sort_order = ord orelse .desc;
        } else if (std.mem.eql(u8, val, "mtime")) {
            config.sort_col = .mtime;
            config.sort_order = ord orelse .asc;
        } else ui.die("Unknown --sort option: {s}.\n", .{val});
    } else if (opt.is("--shared-column")) {
        const val = args.arg();
        if (std.mem.eql(u8, val, "off")) config.show_shared = .off
        else if (std.mem.eql(u8, val, "shared")) config.show_shared = .shared
        else if (std.mem.eql(u8, val, "unique")) config.show_shared = .unique
        else ui.die("Unknown --shared-column option: {s}.\n", .{val});
    } else if (opt.is("--apparent-size")) config.show_blocks = false
    else if (opt.is("--disk-usage")) config.show_blocks = true
    else if (opt.is("-0")) config.scan_ui = .none
    else if (opt.is("-1")) config.scan_ui = .line
    else if (opt.is("-2")) config.scan_ui = .full
    else if (opt.is("--si")) config.si = true
    else if (opt.is("--no-si")) config.si = false
    else if (opt.is("-L") or opt.is("--follow-symlinks")) config.follow_symlinks = true
    else if (opt.is("--no-follow-symlinks")) config.follow_symlinks = false
    else if (opt.is("--exclude")) config.exclude_patterns.append(args.arg()) catch unreachable
    else if (opt.is("-X") or opt.is("--exclude-from")) {
        const arg = args.arg();
        readExcludeFile(arg) catch |e| ui.die("Error reading excludes from {s}: {s}.\n", .{ arg, ui.errorString(e) });
    } else if (opt.is("--exclude-caches")) config.exclude_caches = true
    else if (opt.is("--include-caches")) config.exclude_caches = false
    else if (opt.is("--exclude-kernfs")) config.exclude_kernfs = true
    else if (opt.is("--include-kernfs")) config.exclude_kernfs = false
    else if (opt.is("--confirm-quit")) config.confirm_quit = true
    else if (opt.is("--no-confirm-quit")) config.confirm_quit = false
    else if (opt.is("--confirm-delete")) config.confirm_delete = true
    else if (opt.is("--no-confirm-delete")) config.confirm_delete = false
    else if (opt.is("--color")) {
        const val = args.arg();
        if (std.mem.eql(u8, val, "off")) config.ui_color = .off
        else if (std.mem.eql(u8, val, "dark")) config.ui_color = .dark
        else if (std.mem.eql(u8, val, "dark-bg")) config.ui_color = .darkbg
        else ui.die("Unknown --color option: {s}.\n", .{val});
    } else return false;
    return true;
}

fn tryReadArgsFile(path: [:0]const u8) void {
    var args = Args(ArgsFile).init(ArgsFile.open(path) orelse return);
    while (args.next()) |opt| {
        if (!argConfig(&args, opt))
            ui.die("Uncrecognized option in config file '{s}': {s}.\n", .{path, opt.val});
    }
}

fn version() noreturn {
    std.io.getStdOut().writer().writeAll("ncdu " ++ program_version ++ "\n") catch {};
    std.process.exit(0);
}

fn help() noreturn {
    std.io.getStdOut().writer().writeAll(
        "ncdu <options> <directory>\n\n"
     ++ "  -h,--help                  This help message\n"
     ++ "  -q                         Quiet mode, refresh interval 2 seconds\n"
     ++ "  -v,-V,--version            Print version\n"
     ++ "  -x                         Same filesystem\n"
     ++ "  -e                         Enable extended information\n"
     ++ "  -r                         Read only\n"
     ++ "  -o FILE                    Export scanned directory to FILE\n"
     ++ "  -f FILE                    Import scanned directory from FILE\n"
     ++ "  -0,-1,-2                   UI to use when scanning (0=none,2=full ncurses)\n"
     ++ "  --si                       Use base 10 (SI) prefixes instead of base 2\n"
     ++ "  --exclude PATTERN          Exclude files that match PATTERN\n"
     ++ "  -X, --exclude-from FILE    Exclude files that match any pattern in FILE\n"
     ++ "  -L, --follow-symlinks      Follow symbolic links (excluding directories)\n"
     ++ "  --exclude-caches           Exclude directories containing CACHEDIR.TAG\n"
     ++ "  --exclude-kernfs           Exclude Linux pseudo filesystems (procfs,sysfs,cgroup,...)\n"
     ++ "  --confirm-quit             Confirm quitting ncdu\n"
     ++ "  --color SCHEME             Set color scheme (off/dark/dark-bg)\n"
    ) catch {};
    std.process.exit(0);
}


fn spawnShell() void {
    ui.deinit();
    defer ui.init();

    var path = std.ArrayList(u8).init(allocator);
    defer path.deinit();
    browser.dir_parent.fmtPath(true, &path);

    var env = std.process.getEnvMap(allocator) catch unreachable;
    defer env.deinit();
    // NCDU_LEVEL can only count to 9, keeps the implementation simple.
    if (env.get("NCDU_LEVEL")) |l|
        env.put("NCDU_LEVEL", if (l.len == 0) "1" else switch (l[0]) {
            '0'...'8' => @as([]const u8, &.{l[0]+1}),
            '9' => "9",
            else => "1"
        }) catch unreachable
    else
        env.put("NCDU_LEVEL", "1") catch unreachable;

    const shell = std.os.getenvZ("NCDU_SHELL") orelse std.os.getenvZ("SHELL") orelse "/bin/sh";
    var child = std.ChildProcess.init(&.{shell}, allocator) catch unreachable;
    defer child.deinit();
    child.cwd = path.items;
    child.env_map = &env;

    const term = child.spawnAndWait() catch |e| blk: {
        _ = std.io.getStdErr().writer().print(
            "Error spawning shell: {s}\n\nPress enter to continue.\n",
            .{ ui.errorString(e) }
        ) catch {};
        _ = std.io.getStdIn().reader().skipUntilDelimiterOrEof('\n') catch unreachable;
        break :blk std.ChildProcess.Term{ .Exited = 0 };
    };
    if (term != .Exited) {
        const n = switch (term) {
            .Exited  => "status",
            .Signal  => "signal",
            .Stopped => "stopped",
            .Unknown => "unknown",
        };
        const v = switch (term) {
            .Exited  => |v| v,
            .Signal  => |v| v,
            .Stopped => |v| v,
            .Unknown => |v| v,
        };
        _ = std.io.getStdErr().writer().print(
            "Shell returned with {s} code {}.\n\nPress enter to continue.\n", .{ n, v }
        ) catch {};
        _ = std.io.getStdIn().reader().skipUntilDelimiterOrEof('\n') catch unreachable;
    }
}


fn readExcludeFile(path: [:0]const u8) !void {
    const f = try std.fs.cwd().openFileZ(path, .{});
    defer f.close();
    var rd = std.io.bufferedReader(f.reader()).reader();
    var buf = std.ArrayList(u8).init(allocator);
    while (true) {
        rd.readUntilDelimiterArrayList(&buf, '\n', 4096)
            catch |e| if (e != error.EndOfStream) return e else if (buf.items.len == 0) break;
        if (buf.items.len > 0)
            config.exclude_patterns.append(buf.toOwnedSliceSentinel(0) catch unreachable) catch unreachable;
    }
}

pub fn main() void {
    // Grab thousands_sep from the current C locale.
    _ = c.setlocale(c.LC_ALL, "");
    if (c.localeconv()) |locale| {
        if (locale.*.thousands_sep) |sep| {
            const span = std.mem.spanZ(sep);
            if (span.len > 0)
                config.thousands_sep = span;
        }
    }
    if (std.os.getenvZ("NO_COLOR") == null) config.ui_color = .darkbg;

    tryReadArgsFile("/etc/ncdu.conf");

    if (std.os.getenvZ("XDG_CONFIG_HOME")) |p| {
        var path = std.fs.path.joinZ(allocator, &.{p, "ncdu", "config"}) catch unreachable;
        defer allocator.free(path);
        tryReadArgsFile(path);
    } else if (std.os.getenvZ("HOME")) |p| {
        var path = std.fs.path.joinZ(allocator, &.{p, ".config", "ncdu", "config"}) catch unreachable;
        defer allocator.free(path);
        tryReadArgsFile(path);
    }

    var args = Args(std.process.ArgIteratorPosix).init(std.process.ArgIteratorPosix.init());
    var scan_dir: ?[]const u8 = null;
    var import_file: ?[:0]const u8 = null;
    var export_file: ?[:0]const u8 = null;
    _ = args.next(); // program name
    while (args.next()) |opt| {
        if (!opt.opt) {
            // XXX: ncdu 1.x doesn't error, it just silently ignores all but the last argument.
            if (scan_dir != null) ui.die("Multiple directories given, see ncdu -h for help.\n", .{});
            scan_dir = opt.val;
            continue;
        }
        if (opt.is("-h") or opt.is("-?") or opt.is("--help")) help()
        else if (opt.is("-v") or opt.is("-V") or opt.is("--version")) version()
        else if (opt.is("-o") and export_file != null) ui.die("The -o flag can only be given once.\n", .{})
        else if (opt.is("-o")) export_file = args.arg()
        else if (opt.is("-f") and import_file != null) ui.die("The -f flag can only be given once.\n", .{})
        else if (opt.is("-f")) import_file = args.arg()
        else if (argConfig(&args, opt)) {}
        else ui.die("Unrecognized option '{s}'.\n", .{opt.val});
    }

    if (std.builtin.os.tag != .linux and config.exclude_kernfs)
        ui.die("The --exclude-kernfs tag is currently only supported on Linux.\n", .{});

    const out_tty = std.io.getStdOut().isTty();
    const in_tty = std.io.getStdIn().isTty();
    if (config.scan_ui == null) {
        if (export_file) |f| {
            if (!out_tty or std.mem.eql(u8, f, "-")) config.scan_ui = .none
            else config.scan_ui = .line;
        } else config.scan_ui = .full;
    }
    if (!in_tty and import_file == null and export_file == null)
        ui.die("Standard input is not a TTY. Did you mean to import a file using '-f -'?\n", .{});
    config.nc_tty = !in_tty or (if (export_file) |f| std.mem.eql(u8, f, "-") else false);

    event_delay_timer = std.time.Timer.start() catch unreachable;
    defer ui.deinit();

    var out_file = if (export_file) |f| (
        if (std.mem.eql(u8, f, "-")) std.io.getStdOut()
        else std.fs.cwd().createFileZ(f, .{})
             catch |e| ui.die("Error opening export file: {s}.\n", .{ui.errorString(e)})
    ) else null;

    if (import_file) |f| {
        scan.importRoot(f, out_file);
        config.imported = true;
    } else scan.scanRoot(scan_dir orelse ".", out_file)
           catch |e| ui.die("Error opening directory: {s}.\n", .{ui.errorString(e)});
    if (out_file != null) return;

    config.can_shell = config.can_shell orelse !config.imported;
    config.can_delete = config.can_delete orelse !config.imported;
    config.can_refresh = config.can_refresh orelse !config.imported;

    config.scan_ui = .full; // in case we're refreshing from the UI, always in full mode.
    ui.init();
    state = .browse;
    browser.dir_parent = model.root;
    browser.loadDir(null);

    while (true) {
        switch (state) {
            .refresh => {
                scan.scan();
                state = .browse;
                browser.loadDir(null);
            },
            .shell => {
                spawnShell();
                state = .browse;
            },
            .delete => {
                const next = delete.delete();
                state = .browse;
                browser.loadDir(next);
            },
            else => handleEvent(true, false)
        }
    }
}

var event_delay_timer: std.time.Timer = undefined;

// Draw the screen and handle the next input event.
// In non-blocking mode, screen drawing is rate-limited to keep this function fast.
pub fn handleEvent(block: bool, force_draw: bool) void {
    if (block or force_draw or event_delay_timer.read() > config.update_delay) {
        if (ui.inited) _ = ui.c.erase();
        switch (state) {
            .scan, .refresh => scan.draw(),
            .browse => browser.draw(),
            .delete => delete.draw(),
            .shell => unreachable,
        }
        if (ui.inited) _ = ui.c.refresh();
        event_delay_timer.reset();
    }
    if (!ui.inited) {
        std.debug.assert(!block);
        return;
    }

    var firstblock = block;
    while (true) {
        var ch = ui.getch(firstblock);
        if (ch == 0) return;
        if (ch == -1) return handleEvent(firstblock, true);
        switch (state) {
            .scan, .refresh => scan.keyInput(ch),
            .browse => browser.keyInput(ch),
            .delete => delete.keyInput(ch),
            .shell => unreachable,
        }
        firstblock = false;
    }
}


test "argument parser" {
    const L = struct {
        lst: []const [:0]const u8,
        idx: usize = 0,
        fn next(s: *@This()) ?[:0]const u8 {
            if (s.idx == s.lst.len) return null;
            defer s.idx += 1;
            return s.lst[s.idx];
        }
    };
    const lst = [_][:0]const u8{ "a", "-abcd=e", "--opt1=arg1", "--opt2", "arg2", "-x", "foo", "", "--", "--arg", "", "-", };
    const l = L{ .lst = &lst };
    const T = struct {
        a: Args(L),
        fn opt(self: *@This(), isopt: bool, val: []const u8) !void {
            const o = self.a.next().?;
            try std.testing.expectEqual(isopt, o.opt);
            try std.testing.expectEqualStrings(val, o.val);
            try std.testing.expectEqual(o.is(val), isopt);
        }
        fn arg(self: *@This(), val: []const u8) !void {
            try std.testing.expectEqualStrings(val, self.a.arg());
        }
    };
    var t = T{ .a = Args(L).init(l) };
    try t.opt(false, "a");
    try t.opt(true, "-a");
    try t.opt(true, "-b");
    try t.arg("cd=e");
    try t.opt(true, "--opt1");
    try t.arg("arg1");
    try t.opt(true, "--opt2");
    try t.arg("arg2");
    try t.opt(true, "-x");
    try t.arg("foo");
    try t.opt(false, "");
    try t.opt(false, "--arg");
    try t.opt(false, "");
    try t.opt(false, "-");
    try std.testing.expectEqual(t.a.next(), null);
}