Why are Sinks responsible for maintaining statistics, when isn't part of the Sink trait definition?

[BatmanAoD]

I'm trying to understand how the printers are used, and I'm looking at search_path and search_reader in search.rs. For both search functions and for all three types of printers, sink.stats() and sink.has_match() are called to populate the fields of the SearchResult object,

But stats() and has_match() are not required by the Sink trait. If sinks are intended to be uniformly responsible for maintaining the search statistics, why not add those functions to the definition of Sink? (Of course, JSONSink.stats() would need to be changed to return an option like the other stats implementations do.) Conversely, if there's intended to be some flexibility around whether or not the Sink trait implements these functions, why not add a separate trait (something like StatsSink or StatsRecorder) to codify this?

[BurntSushi]

why not add a separate trait

When it comes to generics, I never ask "why not." I always ask "why do it in the first place."

Stats don't seem like a fundamental part of "sink" to me. It's true that all of the printers provide stats, but note that not all Sink impls provide stats.

Sorry if this isn't a fulfilling answer, but it really is that simple: IMO you have the burden of proof flipped. :-)

[BatmanAoD]

No, that's fair; I'm approaching this in complete ignorance of the design, and not a lot of concrete Rust experience!

The thing in the code that made me think has_match and stats should be codified as part of a trait is the code duplication on the match-arms in search_path and search_reader. I realize that there are only three arms in each one, and only a couple of lines in each arm, but it does seem a little odd to need to continue that duplication if there are ever more printers added.

[BurntSushi]

It would be very helpful if you used github permalinks to the code you're talking about. It makes your questions a lot more accessible. It would potentially let me answer it in mobile for example.

[BatmanAoD]

@BurntSushi Oh, sure, sorry.

Here are search_path and search_reader: https://github.com/BurntSushi/ripgrep/blob/master/crates/core/search.rs#L474

[BurntSushi]

Ah I see. That level of code duplication doesn't even register for me. It's trivial and localized.

Remember, DRY is a means, not an end. :-)