2 files changed, 38 insertions, 7 deletions

diff --git a/crates/ra_cargo_watch/Cargo.toml b/crates/ra_cargo_watch/Cargo.toml
index 49e06e0d3..dd814fc9d 100644
--- a/crates/ra_cargo_watch/Cargo.toml
+++ b/crates/ra_cargo_watch/Cargo.toml
@@ -11,6 +11,7 @@ log = "0.4.3"
 cargo_metadata = "0.9.1"
 jod-thread = "0.1.0"
 parking_lot = "0.10.0"
+serde_json = "1.0.45"
 
 [dev-dependencies]
 insta = "0.13.0"
diff --git a/crates/ra_cargo_watch/src/lib.rs b/crates/ra_cargo_watch/src/lib.rs
index e7b700c10..ea7ddc86b 100644
--- a/crates/ra_cargo_watch/src/lib.rs
+++ b/crates/ra_cargo_watch/src/lib.rs
@@ -9,7 +9,7 @@ use lsp_types::{
 };
 use std::{
     collections::HashMap,
-    io::BufReader,
+    io::{BufRead, BufReader},
     path::PathBuf,
     process::{Command, Stdio},
     sync::Arc,
@@ -216,8 +216,10 @@ impl CheckWatcherThread {
                 self.last_update_req.take();
                 task_send.send(CheckTask::ClearDiagnostics).unwrap();
 
-                // By replacing the watcher, we drop the previous one which
-                // causes it to shut down automatically.
+                // Replace with a dummy watcher first so we drop the original and wait for completion
+                std::mem::replace(&mut self.watcher, WatchThread::dummy());
+
+                // Then create the actual new watcher
                 self.watcher = WatchThread::new(&self.options, &self.workspace_root);
             }
         }
@@ -348,17 +350,45 @@ impl WatchThread {
             // which will break out of the loop, and continue the shutdown
             let _ = message_send.send(CheckEvent::Begin);
 
-            for message in
-                cargo_metadata::parse_messages(BufReader::new(command.stdout.take().unwrap()))
-            {
+            // We manually read a line at a time, instead of using serde's
+            // stream deserializers, because the deserializer cannot recover
+            // from an error, resulting in it getting stuck, because we try to
+            // be resillient against failures.
+            //
+            // Because cargo only outputs one JSON object per line, we can
+            // simply skip a line if it doesn't parse, which just ignores any
+            // erroneus output.
+            let stdout = BufReader::new(command.stdout.take().unwrap());
+            for line in stdout.lines() {
+                let line = match line {
+                    Ok(line) => line,
+                    Err(err) => {
+                        log::error!("Couldn't read line from cargo: {}", err);
+                        continue;
+                    }
+                };
+
+                let message = serde_json::from_str::<cargo_metadata::Message>(&line);
                 let message = match message {
                     Ok(message) => message,
                     Err(err) => {
-                        log::error!("Invalid json from cargo check, ignoring: {}", err);
+                        log::error!(
+                            "Invalid json from cargo check, ignoring ({}): {:?} ",
+                            err,
+                            line
+                        );
                         continue;
                     }
                 };
 
+                // Skip certain kinds of messages to only spend time on what's useful
+                match &message {
+                    Message::CompilerArtifact(artifact) if artifact.fresh => continue,
+                    Message::BuildScriptExecuted(_) => continue,
+                    Message::Unknown => continue,
+                    _ => {}
+                }
+
                 match message_send.send(CheckEvent::Msg(message)) {
                     Ok(()) => {}
                     Err(_err) => {