Auto merge of #138907 - GuillaumeGomez:rfc-3631, r=fmease,camelid,Manishearth,lolbinarycat

Implement RFC 3631: add rustdoc doc_cfg features

Implementation of https://github.com/rust-lang/rfcs/pull/3631.

This implementation actually resulted in a lot of simplifications:
 * All `cfg` computation is now done in one place: `propagate_doc_cfg.rs`. Because (trait) `impl`s are not retrieved at the same time as the other items, we cannot perform this computation in the clean process, it needs to be after.
 * Because there is `cfg` inheritance, we can keep track of them in one place (in `propagate_doc_cfg.rs`), meaning we don't need to copy an item's attributes to its children anymore. Only exception: impl items. For them we clone only `cfg` attributes.
 * `propagate_doc_cfg.rs` is also now much simpler, much less need to keep track of parents, since everything we need is handled by the new `CfgInfo` type.
 * I also suspect that `Cfg::simplify_with` could either be removed or at least used directly into `propagate_doc_cfg.rs` when we compute `cfg`s. Considering how big the PR already is, I'll do it in a follow-up.

I didn't remove the `doc_cfg*` features in this PR because some dependencies used in `rustc` (like `stdarch`) are using it, so we need to have a nightly released with this PR before I can switch to the new feature.

r? ghost

1 files changed, 77 insertions, 0 deletions

diff --git a/tests/rustdoc/doc_auto_cfg.rs b/tests/rustdoc/doc_auto_cfg.rs
new file mode 100644
index 00000000000..19ef174c177
--- /dev/null
+++ b/tests/rustdoc/doc_auto_cfg.rs
@@ -0,0 +1,77 @@
+// Test covering RFC 3631 features.
+
+#![crate_name = "foo"]
+#![feature(doc_cfg)]
+#![doc(auto_cfg(hide(feature = "hidden")))]
+
+//@ has 'foo/index.html'
+//@ !has - '//*[@class="stab portability"]' 'Non-moustache'
+//@ has - '//*[@class="stab portability"]' 'Non-pistache'
+//@ count - '//*[@class="stab portability"]' 1
+
+//@ has 'foo/m/index.html'
+//@ count - '//*[@title="Available on non-crate feature `hidden` only"]' 2
+#[cfg(not(feature = "hidden"))]
+pub mod m {
+    //@ count 'foo/m/struct.A.html' '//*[@class="stab portability"]' 0
+    pub struct A;
+
+    //@ has 'foo/m/inner/index.html' '//*[@class="stab portability"]' 'Available on non-crate feature hidden only.'
+    #[doc(auto_cfg(show(feature = "hidden")))]
+    pub mod inner {
+        //@ has 'foo/m/inner/struct.B.html' '//*[@class="stab portability"]' 'Available on non-crate feature hidden only.'
+        pub struct B;
+
+        //@ count 'foo/m/inner/struct.A.html' '//*[@class="stab portability"]' 0
+        #[doc(auto_cfg(hide(feature = "hidden")))]
+        pub struct A;
+    }
+
+    //@ has 'foo/m/struct.B.html' '//*[@class="stab portability"]' 'Available on non-crate feature hidden only.'
+    #[doc(auto_cfg(show(feature = "hidden")))]
+    pub struct B;
+}
+
+//@ count 'foo/n/index.html' '//*[@title="Available on non-crate feature `moustache` only"]' 3
+//@ count - '//dl/dt' 4
+#[cfg(not(feature = "moustache"))]
+#[doc(auto_cfg = false)]
+pub mod n {
+    // Should not have `moustache` listed.
+    //@ count 'foo/n/struct.X.html' '//*[@class="stab portability"]' 0
+    pub struct X;
+
+    // Should re-enable `auto_cfg` and make `moustache` listed.
+    //@ has 'foo/n/struct.Y.html' '//*[@class="stab portability"]' \
+    //  'Available on non-crate feature moustache only.'
+    #[doc(auto_cfg)]
+    pub struct Y;
+
+    // Should re-enable `auto_cfg` and make `moustache` listed for itself
+    // and for `Y`.
+    //@ has 'foo/n/inner/index.html' '//*[@class="stab portability"]' \
+    //  'Available on non-crate feature moustache only.'
+    #[doc(auto_cfg = true)]
+    pub mod inner {
+        //@ has 'foo/n/inner/struct.Y.html' '//*[@class="stab portability"]' \
+        //  'Available on non-crate feature moustache only.'
+        pub struct Y;
+    }
+
+    // Should re-enable `auto_cfg` and make `moustache` listed.
+    //@ has 'foo/n/struct.Z.html' '//*[@class="stab portability"]' \
+    //  'Available on non-crate feature moustache only.'
+    #[doc(auto_cfg(hide(feature = "hidden")))]
+    pub struct Z;
+}
+
+// Checking inheritance.
+//@ has 'foo/o/index.html' '//*[@class="stab portability"]' \
+//  'Available on non-crate feature pistache only.'
+#[doc(cfg(not(feature = "pistache")))]
+pub mod o {
+    //@ has 'foo/o/struct.A.html' '//*[@class="stab portability"]' \
+    //  'Available on non-crate feature pistache and non-crate feature tarte only.'
+    #[doc(cfg(not(feature = "tarte")))]
+    pub struct A;
+}