ra_cargo_watch: return Result<> from run_cargo(), and don't read stderr for now

As stated by matklad, reading the stderr
should be done alngside with
stdout via select() (or I guess poll()),
there is no such implementation in stdlib,
since it is quite low level and platform-dependent and it
also requires quite a bit of unrelated code we don't use it for now.

As referenced by bjorn3, there is an implementation of the needed read2() function
in rustc compiletest. The better solution will be to extract this function
to a separate crate in future:
https://github.com/rust-analyzer/rust-analyzer/pull/3632#discussion_r395605298

1 files changed, 13 insertions, 14 deletions

diff --git a/crates/ra_project_model/src/cargo_workspace.rs b/crates/ra_project_model/src/cargo_workspace.rs
index c2857dbfc..c7f9bd873 100644
--- a/crates/ra_project_model/src/cargo_workspace.rs
+++ b/crates/ra_project_model/src/cargo_workspace.rs
@@ -6,7 +6,7 @@ use std::{
 };
 
 use anyhow::{Context, Result};
-use cargo_metadata::{CargoOpt, Message, MetadataCommand, PackageId};
+use cargo_metadata::{BuildScript, CargoOpt, Message, MetadataCommand, PackageId};
 use ra_arena::{Arena, Idx};
 use ra_cargo_watch::run_cargo;
 use ra_db::Edition;
@@ -254,7 +254,7 @@ pub fn load_out_dirs(
         "check".to_string(),
         "--message-format=json".to_string(),
         "--manifest-path".to_string(),
-        format!("{}", cargo_toml.display()),
+        cargo_toml.display().to_string(),
     ];
 
     if cargo_features.all_features {
@@ -263,19 +263,15 @@ pub fn load_out_dirs(
         // FIXME: `NoDefaultFeatures` is mutual exclusive with `SomeFeatures`
         // https://github.com/oli-obk/cargo_metadata/issues/79
         args.push("--no-default-features".to_string());
-    } else if !cargo_features.features.is_empty() {
-        for feature in &cargo_features.features {
-            args.push(feature.clone());
-        }
+    } else {
+        args.extend(cargo_features.features.iter().cloned());
     }
 
-    let mut res = FxHashMap::default();
-    let mut child = run_cargo(&args, cargo_toml.parent(), &mut |message| {
+    let mut acc = FxHashMap::default();
+    let res = run_cargo(&args, cargo_toml.parent(), &mut |message| {
         match message {
-            Message::BuildScriptExecuted(message) => {
-                let package_id = message.package_id;
-                let out_dir = message.out_dir;
-                res.insert(package_id, out_dir);
+            Message::BuildScriptExecuted(BuildScript { package_id, out_dir, .. }) => {
+                acc.insert(package_id, out_dir);
             }
 
             Message::CompilerArtifact(_) => (),
@@ -285,6 +281,9 @@ pub fn load_out_dirs(
         true
     });
 
-    let _ = child.wait();
-    res
+    if let Err(err) = res {
+        log::error!("Failed to load outdirs: {:?}", err);
+    }
+
+    acc
 }