Cache outout of 'rustdoc --crate-type proc-macro --help'

Author: Aaron1011

src/cargo/core/compiler/build_context/mod.rs

@@ -1,6 +1,7 @@
 use std::collections::HashMap;
 use std::path::{Path, PathBuf};
 use std::str;
+use std::rc::Rc;
 
 use log::debug;
 
@@ -33,7 +34,7 @@ pub struct BuildContext<'a, 'cfg> {
     pub packages: &'a PackageSet<'cfg>,
 
     /// Information about the compiler.
-    pub rustc: Rustc,
+    pub rustc: Rc<Rustc>,
     /// Build information for the host arch.
     pub host_config: TargetConfig,
     /// Build information for the target.
@@ -53,7 +54,7 @@ impl<'a, 'cfg> BuildContext<'a, 'cfg> {
         units: &'a UnitInterner<'a>,
         extra_compiler_args: HashMap<Unit<'a>, Vec<String>>,
     ) -> CargoResult<BuildContext<'a, 'cfg>> {
-        let rustc = config.load_global_rustc(Some(ws))?;
+        let rustc = Rc::new(config.load_global_rustc(Some(ws))?);
 
         let host_config = TargetConfig::new(config, &rustc.host)?;
         let target_config = match build_config.requested_target.as_ref() {

src/cargo/core/compiler/build_context/target_info.rs

@@ -7,9 +7,7 @@ use std::str::{self, FromStr};
 use crate::core::compiler::Kind;
 use crate::core::TargetKind;
 use crate::util::CfgExpr;
-use crate::util::{
-    process as process_, CargoResult, CargoResultExt, Cfg, Config, ProcessBuilder, Rustc,
-};
+use crate::util::{CargoResult, CargoResultExt, Cfg, Config, ProcessBuilder, Rustc};
 
 /// Information about the platform target gleaned from querying rustc.
 ///
@@ -37,7 +35,6 @@ pub struct TargetInfo {
     /// Extra flags to pass to `rustdoc`, see `env_args`.
     pub rustdocflags: Vec<String>,
     pub supports_pipelining: Option<bool>,
-    pub supports_rustdoc_crate_type: bool,
 }
 
 /// Kind of each file generated by a Unit, part of `FileType`.
@@ -117,12 +114,6 @@ impl TargetInfo {
             Kind::Target => None,
         };
 
-        // NOTE: set this unconditionally to 'true' once support for '--crate-type'
-        // on rustdoc rides to stable.
-        let mut crate_type_test = process_(config.rustdoc()?);
-        crate_type_test.args(&["--crate-type", "proc-macro", "--help"]);
-        let supports_rustdoc_crate_type = crate_type_test.exec_with_output().is_ok();
-
         let target_triple = requested_target
             .as_ref()
             .map(|s| s.as_str())
@@ -213,7 +204,6 @@ impl TargetInfo {
             )?,
             cfg,
             supports_pipelining,
-            supports_rustdoc_crate_type,
         })
     }
 

src/cargo/core/compiler/compilation.rs

@@ -2,12 +2,13 @@ use std::collections::{BTreeSet, HashMap, HashSet};
 use std::env;
 use std::ffi::OsStr;
 use std::path::PathBuf;
+use std::rc::Rc;
 
 use semver::Version;
 
 use super::BuildContext;
 use crate::core::{Edition, InternedString, Package, PackageId, Target};
-use crate::util::{self, join_paths, process, CargoResult, CfgExpr, Config, ProcessBuilder};
+use crate::util::{self, join_paths, process, CargoResult, CfgExpr, Config, ProcessBuilder, rustc::Rustc};
 
 pub struct Doctest {
     /// The package being doc-tested.
@@ -73,7 +74,7 @@ pub struct Compilation<'cfg> {
     primary_unit_rustc_process: Option<ProcessBuilder>,
 
     target_runner: Option<(PathBuf, Vec<String>)>,
-    supports_rustdoc_crate_type: bool,
+    rustc: Rc<Rustc>
 }
 
 impl<'cfg> Compilation<'cfg> {
@@ -110,7 +111,7 @@ impl<'cfg> Compilation<'cfg> {
             host: bcx.host_triple().to_string(),
             target: bcx.target_triple().to_string(),
             target_runner: target_runner(bcx)?,
-            supports_rustdoc_crate_type: bcx.target_info.supports_rustdoc_crate_type,
+            rustc: bcx.rustc.clone()
         })
     }
 
@@ -136,14 +137,25 @@ impl<'cfg> Compilation<'cfg> {
         Ok(p)
     }
 
+    fn supports_rustdoc_crate_type(&self) -> CargoResult<bool> {
+        // NOTE: Unconditionally return 'true' once support for
+        // rustdoc '--crate-type' rides to stable
+        let mut crate_type_test = process(self.config.rustdoc()?);
+        // If '--crate-type' is not supported by rustcoc, this command
+        // will exit with an error. Otherwise, it will print a help message,
+        // and exit successfully
+        crate_type_test.args(&["--crate-type", "proc-macro", "--help"]);
+        Ok(self.rustc.cached_output(&crate_type_test).is_ok())
+    }
+
     /// See `process`.
     pub fn rustdoc_process(&self, pkg: &Package, target: &Target) -> CargoResult<ProcessBuilder> {
         let mut p = self.fill_env(process(&*self.config.rustdoc()?), pkg, false)?;
         if target.edition() != Edition::Edition2015 {
             p.arg(format!("--edition={}", target.edition()));
         }
 
-        if self.supports_rustdoc_crate_type {
+        if self.supports_rustdoc_crate_type()? {
             for crate_type in target.rustc_crate_types() {
                 p.arg("--crate-type").arg(crate_type);
             }