Auto merge of #34045 - ollie27:rustdoc_stripped, r=brson

rustdoc: Don't generate empty files for stripped items

We need to traverse stripped modules to generate redirect pages, but we shouldn't generate
anything else for them.

This now renders the file contents to a Vec before writing it to a file in one go. I think
that's probably a better strategy anyway.

Fixes: #34025

src/librustdoc/html/render.rs

@@ -1257,7 +1257,6 @@ impl Context {
 
         info!("Recursing into {}", self.dst.display());
 
-        mkdir(&self.dst).unwrap();
         let ret = f(self);
 
         info!("Recursed; leaving {}", self.dst.display());
@@ -1301,7 +1300,7 @@ impl Context {
     fn item<F>(&mut self, item: clean::Item, mut f: F) -> Result<(), Error> where
         F: FnMut(&mut Context, clean::Item),
     {
-        fn render(w: File, cx: &Context, it: &clean::Item,
+        fn render(writer: &mut io::Write, cx: &Context, it: &clean::Item,
                   pushname: bool) -> io::Result<()> {
             // A little unfortunate that this is done like this, but it sure
             // does make formatting *a lot* nicer.
@@ -1336,12 +1335,8 @@ impl Context {
 
             reset_ids(true);
 
-            // We have a huge number of calls to write, so try to alleviate some
-            // of the pain by using a buffered writer instead of invoking the
-            // write syscall all the time.
-            let mut writer = BufWriter::new(w);
             if !cx.render_redirect_pages {
-                layout::render(&mut writer, &cx.shared.layout, &page,
+                layout::render(writer, &cx.shared.layout, &page,
                                &Sidebar{ cx: cx, item: it },
                                &Item{ cx: cx, item: it },
                                cx.shared.css_file_extension.is_some())?;
@@ -1354,10 +1349,10 @@ impl Context {
                         url.push_str("/");
                     }
                     url.push_str(&item_path(it));
-                    layout::redirect(&mut writer, &url)?;
+                    layout::redirect(writer, &url)?;
                 }
             }
-            writer.flush()
+            Ok(())
         }
 
         // Stripped modules survive the rustdoc passes (i.e. `strip-private`)
@@ -1378,9 +1373,16 @@ impl Context {
             let mut item = Some(item);
             self.recurse(name, |this| {
                 let item = item.take().unwrap();
-                let joint_dst = this.dst.join("index.html");
-                let dst = try_err!(File::create(&joint_dst), &joint_dst);
-                try_err!(render(dst, this, &item, false), &joint_dst);
+
+                let mut buf = Vec::new();
+                render(&mut buf, this, &item, false).unwrap();
+                // buf will be empty if the module is stripped and there is no redirect for it
+                if !buf.is_empty() {
+                    let joint_dst = this.dst.join("index.html");
+                    try_err!(fs::create_dir_all(&this.dst), &this.dst);
+                    let mut dst = try_err!(File::create(&joint_dst), &joint_dst);
+                    try_err!(dst.write_all(&buf), &joint_dst);
+                }
 
                 let m = match item.inner {
                     clean::StrippedItem(box clean::ModuleItem(m)) |
@@ -1389,7 +1391,7 @@ impl Context {
                 };
 
                 // render sidebar-items.js used throughout this module
-                {
+                if !this.render_redirect_pages {
                     let items = this.build_sidebar_items(&m);
                     let js_dst = this.dst.join("sidebar-items.js");
                     let mut js_out = BufWriter::new(try_err!(File::create(&js_dst), &js_dst));
@@ -1403,10 +1405,15 @@ impl Context {
                 Ok(())
             })
         } else if item.name.is_some() {
-            let joint_dst = self.dst.join(&item_path(&item));
-
-            let dst = try_err!(File::create(&joint_dst), &joint_dst);
-            try_err!(render(dst, self, &item, true), &joint_dst);
+            let mut buf = Vec::new();
+            render(&mut buf, self, &item, true).unwrap();
+            // buf will be empty if the item is stripped and there is no redirect for it
+            if !buf.is_empty() {
+                let joint_dst = self.dst.join(&item_path(&item));
+                try_err!(fs::create_dir_all(&self.dst), &self.dst);
+                let mut dst = try_err!(File::create(&joint_dst), &joint_dst);
+                try_err!(dst.write_all(&buf), &joint_dst);
+            }
             Ok(())
         } else {
             Ok(())

src/test/rustdoc/issue-34025.rs

@@ -0,0 +1,22 @@
+// 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.
+
+#![crate_name = "foo"]
+
+// @!has 'foo/sys/index.html'
+// @!has 'foo/sys/sidebar-items.js'
+#[doc(hidden)]
+pub mod sys {
+    extern "C" {
+        // @!has 'foo/sys/fn.foo.html'
+        #[doc(hidden)]
+        pub fn foo();
+    }
+}