let rustdoc print the crate version into docs

src/bootstrap/bin/rustdoc.rs

@@ -48,6 +48,14 @@ fn main() {
         cmd.arg("-Z").arg("force-unstable-if-unmarked");
     }
 
+    // Bootstrap's Cargo-command builder sets this variable to the current Rust version; let's pick
+    // it up so we can make rustdoc print this into the docs
+    if let Some(version) = env::var_os("RUSTDOC_CRATE_VERSION") {
+        // This "unstable-options" can be removed when `--crate-version` is stabilized
+        cmd.arg("-Z").arg("unstable-options")
+           .arg("--crate-version").arg(version);
+    }
+
     std::process::exit(match cmd.status() {
         Ok(s) => s.code().unwrap_or(1),
         Err(e) => panic!("\n\nfailed to run {:?}: {}\n\n", cmd, e),

src/bootstrap/builder.rs

@@ -418,7 +418,8 @@ impl<'a> Builder<'a> {
             .env("RUSTC_SYSROOT", self.sysroot(compiler))
             .env("RUSTC_LIBDIR", self.sysroot_libdir(compiler, self.build.build))
             .env("CFG_RELEASE_CHANNEL", &self.build.config.channel)
-            .env("RUSTDOC_REAL", self.rustdoc(host));
+            .env("RUSTDOC_REAL", self.rustdoc(host))
+            .env("RUSTDOC_CRATE_VERSION", self.build.rust_version());
         cmd
     }
 
@@ -574,6 +575,9 @@ impl<'a> Builder<'a> {
             cargo.env("RUSTC_SAVE_ANALYSIS", "api".to_string());
         }
 
+        // For `cargo doc` invocations, make rustdoc print the Rust version into the docs
+        cargo.env("RUSTDOC_CRATE_VERSION", self.build.rust_version());
+
         // Environment variables *required* throughout the build
         //
         // FIXME: should update code to not require this env var

src/librustdoc/clean/mod.rs

@@ -112,6 +112,7 @@ impl<T: Clean<U>, U> Clean<Vec<U>> for P<[T]> {
 #[derive(Clone, Debug)]
 pub struct Crate {
     pub name: String,
+    pub version: Option<String>,
     pub src: PathBuf,
     pub module: Option<Item>,
     pub externs: Vec<(CrateNum, ExternalCrate)>,
@@ -183,6 +184,7 @@ impl<'a, 'tcx> Clean<Crate> for visit_ast::RustdocVisitor<'a, 'tcx> {
 
         Crate {
             name,
+            version: None,
             src,
             module: Some(module),
             externs,

src/librustdoc/html/render.rs

@@ -256,6 +256,9 @@ pub struct Cache {
     // the access levels from crateanalysis.
     pub access_levels: Arc<AccessLevels<DefId>>,
 
+    /// The version of the crate being documented, if given fron the `--crate-version` flag.
+    pub crate_version: Option<String>,
+
     // Private fields only used when initially crawling a crate to build a cache
 
     stack: Vec<String>,
@@ -534,6 +537,7 @@ pub fn run(mut krate: clean::Crate,
         primitive_locations: FxHashMap(),
         stripped_mod: false,
         access_levels: krate.access_levels.clone(),
+        crate_version: krate.version.take(),
         orphan_impl_items: Vec::new(),
         traits: mem::replace(&mut krate.external_traits, FxHashMap()),
         deref_trait_did,
@@ -3422,6 +3426,16 @@ impl<'a> fmt::Display for Sidebar<'a> {
             write!(fmt, "{}", it.name.as_ref().unwrap())?;
             write!(fmt, "</p>")?;
 
+            if it.is_crate() {
+                if let Some(ref version) = cache().crate_version {
+                    write!(fmt,
+                           "<div class='block version'>\
+                            <p>Version {}</p>\
+                            </div>",
+                           version)?;
+                }
+            }
+
             match it.inner {
                 clean::StructItem(ref s) => sidebar_struct(fmt, it, s)?,
                 clean::TraitItem(ref t) => sidebar_trait(fmt, it, t)?,

src/librustdoc/html/static/rustdoc.css

@@ -203,6 +203,15 @@ nav.sub {
 	word-wrap: break-word;
 }
 
+.sidebar .version {
+	font-size: 15px;
+	text-align: center;
+	border-bottom: #DDDDDD 1px solid;
+	overflow-wrap: break-word;
+	word-wrap: break-word; /* deprecated */
+	word-break: break-word; /* Chrome, non-standard */
+}
+
 .location:empty {
 	border: none;
 }

src/librustdoc/lib.rs

@@ -243,6 +243,9 @@ pub fn opts() -> Vec<RustcOptGroup> {
         unstable("display-warnings", |o| {
             o.optflag("", "display-warnings", "to print code warnings when testing doc")
         }),
+        unstable("crate-version", |o| {
+            o.optopt("", "crate-version", "crate version to print into documentation", "VERSION")
+        }),
     ]
 }
 
@@ -460,6 +463,7 @@ where R: 'static + Send, F: 'static + Send + FnOnce(Output) -> R {
     let triple = matches.opt_str("target");
     let maybe_sysroot = matches.opt_str("sysroot").map(PathBuf::from);
     let crate_name = matches.opt_str("crate-name");
+    let crate_version = matches.opt_str("crate-version");
     let plugin_path = matches.opt_str("plugin-path");
 
     let cr = PathBuf::from(cratefile);
@@ -484,6 +488,8 @@ where R: 'static + Send, F: 'static + Send + FnOnce(Output) -> R {
             krate.name = name
         }
 
+        krate.version = crate_version;
+
         // Process all of the crate attributes, extracting plugin metadata along
         // with the passes which we are supposed to run.
         for attr in krate.module.as_ref().unwrap().attrs.lists("doc") {

src/test/rustdoc/crate-version.rs

@@ -0,0 +1,13 @@
+// Copyright 2016 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.
+
+// compile-flags: --crate-version=1.3.37 -Z unstable-options
+
+// @has 'crate_version/index.html' '//div[@class="block version"]/p' 'Version 1.3.37'