Explicitly passing an empty string as a []const u8 value causes index out of bounds error during parsing

[tranzystorekk]

Minimal repro example:

const std = @import("std");
const builtin = @import("builtin");

const cova = @import("cova");

const CommandT = cova.Command.Base();
const ValueT = CommandT.ValueT;

const setup_cmd = CommandT{
    .name = "foo",
    .vals = &.{
        ValueT.ofType([]const u8, .{
            .name = "arg",
        }),
    },
};

pub fn main() !void {
    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
    const alloc = gpa.allocator();

    const stdout = std.io.getStdOut().writer();
    const stderr = std.io.getStdErr().writer();

    const cmd = try setup_cmd.init(alloc, .{});
    defer cmd.deinit();

    var args_iter = try cova.ArgIteratorGeneric.init(alloc);
    defer args_iter.deinit();

    cova.parseArgs(&args_iter, CommandT, cmd, stdout, .{}) catch |err| switch (err) {
        error.UsageHelpCalled => return,
        else => return err,
    };

    if (builtin.mode == .Debug) {
        try cova.utils.displayCmdInfo(CommandT, cmd, alloc, &stderr, false);
    }
}

Building this program with cova 0.10.1-beta and running it as prog "" causes the following error:

❯ zig-out/bin/cova-empty-string ""
debug(cova): Parsing Command 'foo'...
debug(cova): Initial Arg: zig-out/bin/cova-empty-string
debug(cova): Current Arg:
debug(cova): Attempting to Parse Commands...
debug(cova): No Commands Matched for Command 'foo'.
debug(cova): Attempting to Parse Options...
thread 20089 panic: index out of bounds: index 2, len 1
/home/devuser/.cache/zig/p/12202782cc66e88f0c15b9acea9d6d1d50dbe941d68b5297927243f6d0377dbb1123/src/cova.zig:419:41: 0x1094329 in parseArgsCtx__anon_5016 (cova-empty-string
)
                    if (!mem.eql(u8, arg[0..long_pf.len], long_pf)) break :checkLongOpt;
                                        ^
/home/devuser/.cache/zig/p/12202782cc66e88f0c15b9acea9d6d1d50dbe941d68b5297927243f6d0377dbb1123/src/cova.zig:229:21: 0x1099fc4 in parseArgs__anon_5014 (cova-empty-string)
    try parseArgsCtx(
                    ^
/tmp/cova-empty-string/src/main.zig:31:19: 0x10b60a1 in main (cova-empty-string)
    cova.parseArgs(&args_iter, CommandT, cmd, stdout, .{}) catch |err| switch (err) {
                  ^
/usr/lib/zig/std/start.zig:524:37: 0x1064eb5 in posixCallMainAndExit (cova-empty-string)
            const result = root.main() catch |err| {
                                    ^
/usr/lib/zig/std/start.zig:266:5: 0x10649d1 in _start (cova-empty-string)
    asm volatile (switch (native_arch) {
    ^
???:?:?: 0x1 in ??? (???)
Unwind information for `???:0x1` was not available, trace may be incomplete

zsh: IOT instruction  zig-out/bin/cova-empty-string ""

[00JCIV00]

Good find! That's a logic error in my Option parsing logic. I'll get it fixed when I have a second.