Use of mut self in builders

[Restioson]

Hi! It seems like log4rs uses mut self for many of the config builder methods (such as .appender). It seems that it is preffered to use &mut self for builders: https://aturon.github.io/ownership/builders.html#non-consuming-builders-(preferred):

[sfackler]

You can use them in separate statements:

let mut builder = Config::builder()
    .test_on_check_out(false);
builder = builder.helper_threads(10);
let config = builder.build();

The config contains a couple of bits of owned/non-cloneable data so build can't take &self as the bottom of the section you linked discusses: https://aturon.github.io/ownership/builders.html#consuming-builders:

[Restioson]

Yeah, sorry, got muddled on that bit 😅 (really sorry for the mistake!) The article still seems to reccomend the &mut pattern though. I think this is what derive-builder uses too

[Restioson]

This would remove the need to keep setting the builder in statement form

[estk]

Not sure this is still relevant in 2019... the blog post is gone though.