Do not add --color to rustdoc if it doesn't support it.

We detect this by executing `rustdoc --color never -V` and see if the
result is successful. To avoid repeatedly creating a new process, we
cache the result into `.rustc_info.json`.

Author: kennytm

src/cargo/core/compiler/mod.rs

@@ -13,7 +13,7 @@ use core::profiles::{Lto, Profile};
 use core::{PackageId, Target};
 use util::errors::{CargoResult, CargoResultExt, Internal};
 use util::paths;
-use util::{self, machine_message, Freshness, ProcessBuilder};
+use util::{self, machine_message, Freshness, ProcessBuilder, process};
 use util::{internal, join_paths, profile};
 
 use self::build_plan::BuildPlan;
@@ -583,7 +583,12 @@ fn rustdoc<'a, 'cfg>(cx: &mut Context<'a, 'cfg>, unit: &Unit<'a>) -> CargoResult
     rustdoc.arg("--crate-name").arg(&unit.target.crate_name());
     add_path_args(bcx, unit, &mut rustdoc);
     add_cap_lints(bcx, unit, &mut rustdoc);
-    add_color(bcx, &mut rustdoc);
+
+    let mut can_add_color_process = process(&*bcx.config.rustdoc()?);
+    can_add_color_process.args(&["--color", "never", "-V"]);
+    if bcx.rustc.cached_success(&can_add_color_process)? {
+        add_color(bcx, &mut rustdoc);
+    }
 
     if unit.kind != Kind::Host {
         if let Some(ref target) = bcx.build_config.requested_target {

src/cargo/util/rustc.rs

@@ -4,6 +4,7 @@ use std::path::{Path, PathBuf};
 use std::hash::{Hash, Hasher, SipHasher};
 use std::collections::hash_map::{Entry, HashMap};
 use std::sync::Mutex;
+use std::process::Stdio;
 use std::env;
 
 use serde_json;
@@ -83,6 +84,10 @@ impl Rustc {
     pub fn cached_output(&self, cmd: &ProcessBuilder) -> CargoResult<(String, String)> {
         self.cache.lock().unwrap().cached_output(cmd)
     }
+
+    pub fn cached_success(&self, cmd: &ProcessBuilder) -> CargoResult<bool> {
+        self.cache.lock().unwrap().cached_success(cmd)
+    }
 }
 
 /// It is a well known that `rustc` is not the fastest compiler in the world.
@@ -104,6 +109,7 @@ struct Cache {
 struct CacheData {
     rustc_fingerprint: u64,
     outputs: HashMap<u64, (String, String)>,
+    successes: HashMap<u64, bool>,
 }
 
 impl Cache {
@@ -113,6 +119,7 @@ impl Cache {
                 let empty = CacheData {
                     rustc_fingerprint,
                     outputs: HashMap::new(),
+                    successes: HashMap::new(),
                 };
                 let mut dirty = true;
                 let data = match read(&cache_location) {
@@ -177,6 +184,28 @@ impl Cache {
             }
         }
     }
+
+    fn cached_success(&mut self, cmd: &ProcessBuilder) -> CargoResult<bool> {
+        let key = process_fingerprint(cmd);
+        match self.data.successes.entry(key) {
+            Entry::Occupied(entry) => {
+                info!("rustc info cache hit");
+                Ok(*entry.get())
+            }
+            Entry::Vacant(entry) => {
+                info!("rustc info cache miss");
+                let success = cmd
+                    .build_command()
+                    .stdout(Stdio::null())
+                    .stderr(Stdio::null())
+                    .status()?
+                    .success();
+                entry.insert(success);
+                self.dirty = true;
+                Ok(success)
+            }
+        }
+    }
 }
 
 impl Drop for Cache {

tests/testsuite/rustdoc.rs

@@ -8,7 +8,7 @@ fn rustdoc_simple() {
         .with_stderr(
             "\
 [DOCUMENTING] foo v0.0.1 ([CWD])
-[RUNNING] `rustdoc --crate-name foo src/lib.rs --color never \
+[RUNNING] `rustdoc --crate-name foo src/lib.rs [..]\
         -o [CWD]/target/doc \
         -L dependency=[CWD]/target/debug/deps`
 [FINISHED] dev [unoptimized + debuginfo] target(s) in [..]
@@ -24,7 +24,7 @@ fn rustdoc_args() {
         .with_stderr(
             "\
 [DOCUMENTING] foo v0.0.1 ([CWD])
-[RUNNING] `rustdoc --crate-name foo src/lib.rs --color never \
+[RUNNING] `rustdoc --crate-name foo src/lib.rs [..]\
         -o [CWD]/target/doc \
         --cfg=foo \
         -L dependency=[CWD]/target/debug/deps`
@@ -61,7 +61,7 @@ fn rustdoc_foo_with_bar_dependency() {
 [CHECKING] bar v0.0.1 ([..])
 [RUNNING] `rustc [..]bar/src/lib.rs [..]`
 [DOCUMENTING] foo v0.0.1 ([CWD])
-[RUNNING] `rustdoc --crate-name foo src/lib.rs --color never \
+[RUNNING] `rustdoc --crate-name foo src/lib.rs [..]\
         -o [CWD]/target/doc \
         --cfg=foo \
         -L dependency=[CWD]/target/debug/deps \
@@ -97,7 +97,7 @@ fn rustdoc_only_bar_dependency() {
         .with_stderr(
             "\
 [DOCUMENTING] bar v0.0.1 ([..])
-[RUNNING] `rustdoc --crate-name bar [..]bar/src/lib.rs --color never \
+[RUNNING] `rustdoc --crate-name bar [..]bar/src/lib.rs [..]\
         -o [CWD]/target/doc \
         --cfg=foo \
         -L dependency=[CWD]/target/debug/deps`
@@ -117,7 +117,7 @@ fn rustdoc_same_name_documents_lib() {
         .with_stderr(
             "\
 [DOCUMENTING] foo v0.0.1 ([..])
-[RUNNING] `rustdoc --crate-name foo src/lib.rs --color never \
+[RUNNING] `rustdoc --crate-name foo src/lib.rs [..]\
         -o [CWD]/target/doc \
         --cfg=foo \
         -L dependency=[CWD]/target/debug/deps`
@@ -161,7 +161,7 @@ fn rustdoc_target() {
         .with_stderr(
             "\
 [DOCUMENTING] foo v0.0.1 ([..])
-[RUNNING] `rustdoc --crate-name foo src/lib.rs --color never \
+[RUNNING] `rustdoc --crate-name foo src/lib.rs [..]\
     --target x86_64-unknown-linux-gnu \
     -o [CWD]/target/x86_64-unknown-linux-gnu/doc \
     -L dependency=[CWD]/target/x86_64-unknown-linux-gnu/debug/deps \