Rollup merge of #142472 - GuillaumeGomez:doc-attribute-attribute, r=fmease

Add new `doc(attribute = "...")` attribute

Fixes rust-lang/rust#141123.

The implementation and purpose of this new `#[doc(attribute = "...")]` attribute is very close to `#[doc(keyword = "...")]`. Which means that luckily for us, most of the code needed was already in place and `@Noratrieb` nicely wrote a first draft that helped me implement this new attribute very fast.

Now with all this said, there is one thing I didn't do yet: adding a `rustdoc-js-std` test. I added GUI tests with search results for attributes so should be fine but I still plan on adding one for it once documentation for builtin attributes will be written into the core/std libs.

You can test it [here](https://rustdoc.crud.net/imperio/doc-attribute-attribute/foo/index.html).

cc `@Noratrieb` `@Veykril`

1 files changed, 10 insertions, 0 deletions

diff --git a/tests/rustdoc-ui/invalid-attribute.rs b/tests/rustdoc-ui/invalid-attribute.rs
new file mode 100644
index 00000000000..2fc7be2cf34
--- /dev/null
+++ b/tests/rustdoc-ui/invalid-attribute.rs
@@ -0,0 +1,10 @@
+// Testing the output when an invalid builtin attribute is passed as value
+// to `doc(attribute = "...")`.
+
+#![feature(rustdoc_internals)]
+
+#[doc(attribute = "foo df")] //~ ERROR
+mod foo {}
+
+#[doc(attribute = "fooyi")] //~ ERROR
+mod foo2 {}