Auto merge of #43348 - kennytm:fix-24658-doc-every-platform, r=alexcrichton

Expose all OS-specific modules in libstd doc.

1. Uses the special `--cfg dox` configuration passed by rustbuild when running `rustdoc`. Changes the `#[cfg(platform)]` into `#[cfg(any(dox, platform))]` so that platform-specific API are visible to rustdoc.

2. Since platform-specific implementations often won't compile correctly on other platforms, `rustdoc` is changed to apply `everybody_loops` to the functions during documentation and doc-test harness.

3. Since platform-specific code are documented on all platforms now, it could confuse users who found a useful API but is non-portable. Also, their examples will be doc-tested, so must be excluded when not testing on the native platform. An undocumented attribute `#[doc(cfg(...))]` is introduced to serve the above purposed.

Fixes #24658 (Does _not_ fully implement #1998).

1 files changed, 47 insertions, 0 deletions

diff --git a/src/test/rustdoc/doc-cfg.rs b/src/test/rustdoc/doc-cfg.rs
new file mode 100644
index 00000000000..cfb37912fe7
--- /dev/null
+++ b/src/test/rustdoc/doc-cfg.rs
@@ -0,0 +1,47 @@
+// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(doc_cfg)]
+
+// @has doc_cfg/struct.Portable.html
+// @!has - '//*[@id="main"]/*[@class="stability"]/*[@class="stab portability"]' ''
+// @has - '//*[@id="method.unix_and_arm_only_function"]' 'fn unix_and_arm_only_function()'
+// @has - '//*[@class="stab portability"]' 'This is supported on Unix and ARM only.'
+pub struct Portable;
+
+// @has doc_cfg/unix_only/index.html \
+//  '//*[@id="main"]/*[@class="stability"]/*[@class="stab portability"]' \
+//  'This is supported on Unix only.'
+// @matches - '//*[@class=" module-item"]//*[@class="stab portability"]' '\AUnix\Z'
+// @matches - '//*[@class=" module-item"]//*[@class="stab portability"]' '\AUnix and ARM\Z'
+// @count - '//*[@class="stab portability"]' 3
+#[doc(cfg(unix))]
+pub mod unix_only {
+    // @has doc_cfg/unix_only/fn.unix_only_function.html \
+    //  '//*[@id="main"]/*[@class="stability"]/*[@class="stab portability"]' \
+    //  'This is supported on Unix only.'
+    // @count - '//*[@class="stab portability"]' 1
+    pub fn unix_only_function() {
+        content::should::be::irrelevant();
+    }
+
+    // @has doc_cfg/unix_only/trait.ArmOnly.html \
+    //  '//*[@id="main"]/*[@class="stability"]/*[@class="stab portability"]' \
+    //  'This is supported on Unix and ARM only.'
+    // @count - '//*[@class="stab portability"]' 2
+    #[doc(cfg(target_arch = "arm"))]
+    pub trait ArmOnly {
+        fn unix_and_arm_only_function();
+    }
+
+    impl ArmOnly for super::Portable {
+        fn unix_and_arm_only_function() {}
+    }
+}
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