is there a way to write stub functions in zig?

Question

Just like how Rust offers todo!() or how Ocaml has let func = "Failure "Unimplemented"" is there a way to write a function in zig that doesn't have the body implemented and doesn't raise any warnings and errors after being compiled?

For now I just write it with a print for e.g.

pub fn do_something(self: *MyType) void {
        std.debug.print("TODO %d", self.field);
}

Answer 1

The standard library uses the @compileError builtin to indicate deprecations. You could use this builtin with a "TODO" string:

fn do_something(self: *MyType) void {
    _ = self;
    @compileError("TODO: not yet implemented");
}

Due to Zig's lazy compilation, a compile error will only be thrown if do_something is actually used. You'll still need to discard unused arguments, though. You can avoid this by dropping the function signature and defining do_something as a constant (see std.mem.tokenize).

A slight difference between this and Rust is that this fails to compile, whereas Rust panics. If you prefer panicking over compilation errors, you may use @panic (see std.Target.cTypeBitSize):

fn do_something(self: *MyType) void {
    _ = self;
    @panic("TODO: not yet implemented");
}

A benefit to using @compileError over @panic is that ZLS will catch @compileError at compile time and highlight the symbol as deprecated; see PR #1764 for more info. However, if the code is considered for compilation, it will fail. This makes @panic more flexible and appropriate for the use-case, IMO.