"Auto-hide trait implementation documentation" does nothing

[Nemo157]

beta and nightly ignore the default-on configuration of "Auto-hide trait implementation documentation"

On stable std::future::Pending looks like:

While on beta it looks like:

And on nightly (as of 2021-05-17):

Going to https://doc.rust-lang.org/nightly/settings.html and toggling "Auto-hide trait implementation documentation" off makes stable look the same as beta, so it definitely seems like beta/nightly are just ignoring this toggle.

[jsha]

This is due to the refactoring we've been doing with the expand / collapse toggles, wrapping them in <details> tags. The code that expands and collapses them based on settings is here:

rust/src/librustdoc/html/static/main.js

Lines 909 to 911 in 3e827cc

	var hideMethodDocs = getSettingValue("auto-hide-method-docs") === "true";
	var hideImplementors = getSettingValue("auto-collapse-implementors") !== "false";
	var hideLargeItemContents = getSettingValue("auto-hide-large-items") !== "false";

rust/src/librustdoc/html/static/main.js

Lines 927 to 945 in 3e827cc

	if (hideMethodDocs) {
	onEachLazy(document.getElementsByClassName("method"), function(e) {
	var toggle = e.parentNode;
	if (toggle) {
	toggle = toggle.parentNode;
	}
	if (toggle && toggle.tagName === "DETAILS") {
	toggle.open = false;
	}
	});
	}
	onEachLazy(document.getElementsByTagName("details"), function (e) {
	var showLargeItem = !hideLargeItemContents && hasClass(e, "type-contents-toggle");
	var showImplementor = !hideImplementors && hasClass(e, "implementors-toggle");
	if (showLargeItem || showImplementor) {
	e.open = true;
	}
	});

You can see there's an entry for handling "implementors" but not one for "implementations."

Right now, both implementors and implementations get wrapped in a <details> tag with class=toggle-implementors. We need to update this Rust code:

rust/src/librustdoc/html/render/mod.rs

Lines 1542 to 1549 in 3e827cc

	let open_details = |close_tags: &mut String| {
	if toggled {
	close_tags.insert_str(0, "</details>");
	"<details class=\"rustdoc-toggle implementors-toggle\" open><summary>"
	} else {
	""
	}
	};

So that it generates toggle-implementors for implementors and toggle-implementations for implementations. And then update the JS to add a clause for implementations.

[apiraino]

Assigning priority as discussed in the Zulip thread of the Prioritization Working Group.

@rustbot label -I-prioritize +P-medium

[jsha]

I'm having trouble figuring out what fields to check in render_impl to figure out if we're rendering an implementor or an implementation. If someone's able to point me in the right direction I'd appreciate it!

[GuillaumeGomez]

Well, I think I handled it in #85548 (funny that I was noticed it and fixed it on my side and someone else find it out too).