rustdoc: link to stable/beta docs consistently in documentation

 ## User-facing changes

- Intra-doc links to primitives that currently go to rust-lang.org/nightly/std/primitive.x.html will start going to channel that rustdoc was built with. Nightly will continue going to /nightly; Beta will link to /beta; stable compilers will link to /1.52.1 (or whatever version they were built as).
- Cross-crate links from std to core currently go to /nightly unconditionally. They will start going to /1.52.0 on stable channels (but remain the same on nightly channels).
- Intra-crate links from std to std (or core to core) currently go to the same URL they are hosted at; they will continue to do so. Notably, this is different from everything else because it can preserve the distinction between /stable and /1.52.0 by using relative links.

Note that "links" includes both intra-doc links and rustdoc's own
automatically generated hyperlinks.

 ## Implementation changes

- Update the testsuite to allow linking to /beta and /1.52.1 in docs
- Use an html_root_url for the standard library that's dependent on the channel

  This avoids linking to nightly docs on stable.

- Update rustdoc to use channel-dependent links for primitives from an
  unknown crate

- Set DOC_RUST_LANG_ORG_CHANNEL from bootstrap to ensure it's in sync
- Include doc.rust-lang.org in the channel

library/alloc/src/lib.rs

@@ -59,7 +59,6 @@
 #![allow(unused_attributes)]
 #![stable(feature = "alloc", since = "1.36.0")]
 #![doc(
-    html_root_url = "https://doc.rust-lang.org/nightly/",
     html_playground_url = "https://play.rust-lang.org/",
     issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/",
     test(no_crate_inject, attr(allow(unused_variables), deny(warnings)))

library/core/src/lib.rs

@@ -51,7 +51,6 @@
 #![cfg(not(test))]
 #![stable(feature = "core", since = "1.6.0")]
 #![doc(
-    html_root_url = "https://doc.rust-lang.org/nightly/",
     html_playground_url = "https://play.rust-lang.org/",
     issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/",
     test(no_crate_inject, attr(deny(warnings))),

library/panic_abort/src/lib.rs

@@ -5,10 +5,7 @@
 
 #![no_std]
 #![unstable(feature = "panic_abort", issue = "32837")]
-#![doc(
-    html_root_url = "https://doc.rust-lang.org/nightly/",
-    issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/"
-)]
+#![doc(issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/")]
 #![panic_runtime]
 #![allow(unused_features)]
 #![feature(core_intrinsics)]

library/panic_unwind/src/lib.rs

@@ -13,10 +13,7 @@
 
 #![no_std]
 #![unstable(feature = "panic_unwind", issue = "32837")]
-#![doc(
-    html_root_url = "https://doc.rust-lang.org/nightly/",
-    issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/"
-)]
+#![doc(issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/")]
 #![feature(core_intrinsics)]
 #![feature(lang_items)]
 #![feature(nll)]

library/proc_macro/src/lib.rs

@@ -12,7 +12,6 @@
 #![stable(feature = "proc_macro_lib", since = "1.15.0")]
 #![deny(missing_docs)]
 #![doc(
-    html_root_url = "https://doc.rust-lang.org/nightly/",
     html_playground_url = "https://play.rust-lang.org/",
     issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/",
     test(no_crate_inject, attr(deny(warnings))),

library/std/src/lib.rs

@@ -190,7 +190,6 @@
 #![cfg_attr(not(feature = "restricted-std"), stable(feature = "rust1", since = "1.0.0"))]
 #![cfg_attr(feature = "restricted-std", unstable(feature = "restricted_std", issue = "none"))]
 #![doc(
-    html_root_url = "https://doc.rust-lang.org/nightly/",
     html_playground_url = "https://play.rust-lang.org/",
     issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/",
     test(no_crate_inject, attr(deny(warnings))),

library/term/src/lib.rs

@@ -30,11 +30,7 @@
 //! [win]: https://docs.microsoft.com/en-us/windows/console/character-mode-applications
 //! [ti]: https://en.wikipedia.org/wiki/Terminfo
 
-#![doc(
-    html_root_url = "https://doc.rust-lang.org/nightly/",
-    html_playground_url = "https://play.rust-lang.org/",
-    test(attr(deny(warnings)))
-)]
+#![doc(html_playground_url = "https://play.rust-lang.org/", test(attr(deny(warnings))))]
 #![deny(missing_docs)]
 #![cfg_attr(windows, feature(libc))]
 

library/test/src/lib.rs

@@ -19,7 +19,7 @@
 
 #![crate_name = "test"]
 #![unstable(feature = "test", issue = "50297")]
-#![doc(html_root_url = "https://doc.rust-lang.org/nightly/", test(attr(deny(warnings))))]
+#![doc(test(attr(deny(warnings))))]
 #![cfg_attr(unix, feature(libc))]
 #![feature(rustc_private)]
 #![feature(nll)]

src/bootstrap/builder.rs

@@ -574,6 +574,18 @@ impl<'a> Builder<'a> {
         self.run_step_descriptions(&Builder::get_step_descriptions(Kind::Doc), paths);
     }
 
+    /// NOTE: keep this in sync with `rustdoc::clean::utils::doc_rust_lang_org_channel`, or tests will fail on beta/stable.
+    pub fn doc_rust_lang_org_channel(&self) -> String {
+        let channel = match &*self.config.channel {
+            "stable" => &self.version,
+            "beta" => "beta",
+            "nightly" | "dev" => "nightly",
+            // custom build of rustdoc maybe? link to the latest stable docs just in case
+            _ => "stable",
+        };
+        "https://doc.rust-lang.org/".to_owned() + channel
+    }
+
     fn run_step_descriptions(&self, v: &[StepDescription], paths: &[PathBuf]) {
         StepDescription::run(v, self, paths);
     }

src/bootstrap/compile.rs

@@ -326,6 +326,11 @@ pub fn std_cargo(builder: &Builder<'_>, target: TargetSelection, stage: u32, car
     if target.contains("riscv") {
         cargo.rustflag("-Cforce-unwind-tables=yes");
     }
+
+    let html_root =
+        format!("-Zcrate-attr=doc(html_root_url=\"{}/\")", builder.doc_rust_lang_org_channel(),);
+    cargo.rustflag(&html_root);
+    cargo.rustdocflag(&html_root);
 }
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]

src/bootstrap/test.rs

@@ -1486,6 +1486,7 @@ note: if you're sure you want to do this, please open an issue as to why. In the
             }
         }
         cmd.env("RUSTC_BOOTSTRAP", "1");
+        cmd.env("DOC_RUST_LANG_ORG_CHANNEL", builder.doc_rust_lang_org_channel());
         builder.add_rust_test_threads(&mut cmd);
 
         if builder.config.sanitizers_enabled(target) {

src/bootstrap/tool.rs

@@ -263,6 +263,7 @@ pub fn prepare_tool_cargo(
     cargo.env("CFG_RELEASE_CHANNEL", &builder.config.channel);
     cargo.env("CFG_VERSION", builder.rust_version());
     cargo.env("CFG_RELEASE_NUM", &builder.version);
+    cargo.env("DOC_RUST_LANG_ORG_CHANNEL", builder.doc_rust_lang_org_channel());
 
     let info = GitInfo::new(builder.config.ignore_git, &dir);
     if let Some(sha) = info.sha() {

src/etc/htmldocck.py

@@ -135,6 +135,8 @@
     unichr = chr
 
 
+channel = os.environ["DOC_RUST_LANG_ORG_CHANNEL"]
+
 class CustomHTMLParser(HTMLParser):
     """simplified HTML parser.
 
@@ -270,6 +272,7 @@ def flatten(node):
 
 
 def normalize_xpath(path):
+    path = path.replace("{{channel}}", channel)
     if path.startswith('//'):
         return '.' + path  # avoid warnings
     elif path.startswith('.//'):
@@ -334,6 +337,7 @@ def get_dir(self, path):
 
 
 def check_string(data, pat, regexp):
+    pat = pat.replace("{{channel}}", channel)
     if not pat:
         return True  # special case a presence testing
     elif regexp:

src/librustdoc/clean/types.rs

@@ -499,7 +499,7 @@ impl Item {
                                     format!("{}/std/", s.trim_end_matches('/'))
                                 }
                                 Some(ExternalLocation::Unknown) | None => {
-                                    "https://doc.rust-lang.org/nightly/std/".to_string()
+                                    format!("{}/std/", crate::DOC_RUST_LANG_ORG_CHANNEL)
                                 }
                             };
                             // This is a primitive so the url is done "by hand".

src/librustdoc/clean/utils.rs

@@ -543,3 +543,8 @@ crate fn has_doc_flag(attrs: ty::Attributes<'_>, flag: Symbol) -> bool {
             && attr.meta_item_list().map_or(false, |l| rustc_attr::list_contains_name(&l, flag))
     })
 }
+
+/// A link to `doc.rust-lang.org` that includes the channel name.
+///
+/// Set by `bootstrap::Builder::doc_rust_lang_org_channel` in order to keep tests passing on beta/stable.
+crate const DOC_RUST_LANG_ORG_CHANNEL: &'static str = env!("DOC_RUST_LANG_ORG_CHANNEL");

src/librustdoc/lib.rs

@@ -81,6 +81,8 @@ use rustc_session::config::{make_crate_type_option, ErrorOutputType, RustcOptGro
 use rustc_session::getopts;
 use rustc_session::{early_error, early_warn};
 
+use crate::clean::utils::DOC_RUST_LANG_ORG_CHANNEL;
+
 /// A macro to create a FxHashMap.
 ///
 /// Example:

src/test/rustdoc-ui/check.rs

@@ -1,5 +1,6 @@
 // check-pass
 // compile-flags: -Z unstable-options --check
+// normalize-stderr-test: "nightly|beta|1\.[0-9][0-9]\.[0-9]" -> "$$CHANNEL"
 
 #![warn(missing_docs)]
 //~^ WARN

src/test/rustdoc-ui/check.stderr

@@ -1,5 +1,5 @@
 warning: missing documentation for the crate
-  --> $DIR/check.rs:4:1
+  --> $DIR/check.rs:5:1
    |
 LL | / #![warn(missing_docs)]
 LL | |
@@ -10,30 +10,30 @@ LL | | pub fn foo() {}
    | |_______________^
    |
 note: the lint level is defined here
-  --> $DIR/check.rs:4:9
+  --> $DIR/check.rs:5:9
    |
 LL | #![warn(missing_docs)]
    |         ^^^^^^^^^^^^
 
 warning: missing documentation for a function
-  --> $DIR/check.rs:9:1
+  --> $DIR/check.rs:10:1
    |
 LL | pub fn foo() {}
    | ^^^^^^^^^^^^
 
 warning: no documentation found for this crate's top-level module
    |
 note: the lint level is defined here
-  --> $DIR/check.rs:7:9
+  --> $DIR/check.rs:8:9
    |
 LL | #![warn(rustdoc::all)]
    |         ^^^^^^^^^^^^
    = note: `#[warn(rustdoc::missing_crate_level_docs)]` implied by `#[warn(rustdoc::all)]`
    = help: The following guide may be of use:
-           https://doc.rust-lang.org/nightly/rustdoc/how-to-write-documentation.html
+           https://doc.rust-lang.org/$CHANNEL/rustdoc/how-to-write-documentation.html
 
 warning: missing code example in this documentation
-  --> $DIR/check.rs:4:1
+  --> $DIR/check.rs:5:1
    |
 LL | / #![warn(missing_docs)]
 LL | |
@@ -44,14 +44,14 @@ LL | | pub fn foo() {}
    | |_______________^
    |
 note: the lint level is defined here
-  --> $DIR/check.rs:7:9
+  --> $DIR/check.rs:8:9
    |
 LL | #![warn(rustdoc::all)]
    |         ^^^^^^^^^^^^
    = note: `#[warn(rustdoc::missing_doc_code_examples)]` implied by `#[warn(rustdoc::all)]`
 
 warning: missing code example in this documentation
-  --> $DIR/check.rs:9:1
+  --> $DIR/check.rs:10:1
    |
 LL | pub fn foo() {}
    | ^^^^^^^^^^^^^^^

src/test/rustdoc-ui/intra-doc/email-address-localhost.rs

@@ -1,3 +1,4 @@
+// normalize-stderr-test: "nightly|beta|1\.[0-9][0-9]\.[0-9]" -> "$$CHANNEL"
 #![deny(warnings)]
 
 //! Email me at <hello@localhost>.

src/test/rustdoc-ui/intra-doc/email-address-localhost.stderr

@@ -1,16 +1,16 @@
 error: unknown disambiguator `hello`
-  --> $DIR/email-address-localhost.rs:3:18
+  --> $DIR/email-address-localhost.rs:4:18
    |
 LL | //! Email me at <hello@localhost>.
    |                  ^^^^^
    |
 note: the lint level is defined here
-  --> $DIR/email-address-localhost.rs:1:9
+  --> $DIR/email-address-localhost.rs:2:9
    |
 LL | #![deny(warnings)]
    |         ^^^^^^^^
    = note: `#[deny(rustdoc::broken_intra_doc_links)]` implied by `#[deny(warnings)]`
-   = note: see https://doc.rust-lang.org/nightly/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
+   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
 
 error: aborting due to previous error
 

src/test/rustdoc-ui/intra-doc/unknown-disambiguator.rs

@@ -1,3 +1,4 @@
+// normalize-stderr-test: "nightly|beta|1\.[0-9][0-9]\.[0-9]" -> "$$CHANNEL"
 #![deny(warnings)]
 
 //! Linking to [foo@banana] and [`bar@banana!()`].

src/test/rustdoc-ui/intra-doc/unknown-disambiguator.stderr

@@ -1,56 +1,56 @@
 error: unknown disambiguator `foo`
-  --> $DIR/unknown-disambiguator.rs:3:17
+  --> $DIR/unknown-disambiguator.rs:4:17
    |
 LL | //! Linking to [foo@banana] and [`bar@banana!()`].
    |                 ^^^
    |
 note: the lint level is defined here
-  --> $DIR/unknown-disambiguator.rs:1:9
+  --> $DIR/unknown-disambiguator.rs:2:9
    |
 LL | #![deny(warnings)]
    |         ^^^^^^^^
    = note: `#[deny(rustdoc::broken_intra_doc_links)]` implied by `#[deny(warnings)]`
-   = note: see https://doc.rust-lang.org/nightly/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
+   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
 
 error: unknown disambiguator `bar`
-  --> $DIR/unknown-disambiguator.rs:3:35
+  --> $DIR/unknown-disambiguator.rs:4:35
    |
 LL | //! Linking to [foo@banana] and [`bar@banana!()`].
    |                                   ^^^
    |
-   = note: see https://doc.rust-lang.org/nightly/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
+   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
 
 error: unknown disambiguator `foo`
-  --> $DIR/unknown-disambiguator.rs:9:34
+  --> $DIR/unknown-disambiguator.rs:10:34
    |
 LL | //! And with weird backticks: [``foo@hello``] [foo`@`hello].
    |                                  ^^^
    |
-   = note: see https://doc.rust-lang.org/nightly/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
+   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
 
 error: unknown disambiguator `foo`
-  --> $DIR/unknown-disambiguator.rs:9:48
+  --> $DIR/unknown-disambiguator.rs:10:48
    |
 LL | //! And with weird backticks: [``foo@hello``] [foo`@`hello].
    |                                                ^^^
    |
-   = note: see https://doc.rust-lang.org/nightly/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
+   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
 
 error: unknown disambiguator ``
-  --> $DIR/unknown-disambiguator.rs:6:31
+  --> $DIR/unknown-disambiguator.rs:7:31
    |
 LL | //! And to [no disambiguator](@nectarine) and [another](@apricot!()).
    |                               ^
    |
-   = note: see https://doc.rust-lang.org/nightly/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
+   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
 
 error: unknown disambiguator ``
-  --> $DIR/unknown-disambiguator.rs:6:57
+  --> $DIR/unknown-disambiguator.rs:7:57
    |
 LL | //! And to [no disambiguator](@nectarine) and [another](@apricot!()).
    |                                                         ^
    |
-   = note: see https://doc.rust-lang.org/nightly/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
+   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
 
 error: aborting due to 6 previous errors
 

src/test/rustdoc-ui/no-crate-level-doc-lint.rs

@@ -1,4 +1,5 @@
 // error-pattern: no documentation found
+// normalize-stderr-test: "nightly|beta|1\.[0-9][0-9]\.[0-9]" -> "$$CHANNEL"
 #![deny(rustdoc::missing_crate_level_docs)]
 //^~ NOTE defined here
 

src/test/rustdoc-ui/no-crate-level-doc-lint.stderr

@@ -1,12 +1,12 @@
 error: no documentation found for this crate's top-level module
    |
 note: the lint level is defined here
-  --> $DIR/no-crate-level-doc-lint.rs:2:9
+  --> $DIR/no-crate-level-doc-lint.rs:3:9
    |
 LL | #![deny(rustdoc::missing_crate_level_docs)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = help: The following guide may be of use:
-           https://doc.rust-lang.org/nightly/rustdoc/how-to-write-documentation.html
+           https://doc.rust-lang.org/$CHANNEL/rustdoc/how-to-write-documentation.html
 
 error: aborting due to previous error
 

src/test/rustdoc/intra-doc/associated-items.rs

@@ -3,9 +3,9 @@
 /// [`std::collections::BTreeMap::into_iter`]
 /// [`String::from`] is ambiguous as to which `From` impl
 /// [Vec::into_iter()] uses a disambiguator
-// @has 'associated_items/fn.foo.html' '//a[@href="https://doc.rust-lang.org/nightly/alloc/collections/btree/map/struct.BTreeMap.html#method.into_iter"]' 'std::collections::BTreeMap::into_iter'
-// @has 'associated_items/fn.foo.html' '//a[@href="https://doc.rust-lang.org/nightly/alloc/string/struct.String.html#method.from"]' 'String::from'
-// @has 'associated_items/fn.foo.html' '//a[@href="https://doc.rust-lang.org/nightly/alloc/vec/struct.Vec.html#method.into_iter"]' 'Vec::into_iter'
+// @has 'associated_items/fn.foo.html' '//a[@href="{{channel}}/alloc/collections/btree/map/struct.BTreeMap.html#method.into_iter"]' 'std::collections::BTreeMap::into_iter'
+// @has 'associated_items/fn.foo.html' '//a[@href="{{channel}}/alloc/string/struct.String.html#method.from"]' 'String::from'
+// @has 'associated_items/fn.foo.html' '//a[@href="{{channel}}/alloc/vec/struct.Vec.html#method.into_iter"]' 'Vec::into_iter'
 pub fn foo() {}
 
 /// Link to [MyStruct], [link from struct][MyStruct::method], [MyStruct::clone], [MyStruct::Input]

src/test/rustdoc/intra-doc/builtin-macros.rs

@@ -1,3 +1,3 @@
 // @has builtin_macros/index.html
-// @has - '//a/@href' 'https://doc.rust-lang.org/nightly/core/macro.cfg.html'
+// @has - '//a/@href' '{{channel}}/core/macro.cfg.html'
 //! [cfg]