1 files changed, 27 insertions, 12 deletions

diff --git a/crates/rust-analyzer/src/bin/logger.rs b/crates/rust-analyzer/src/bin/logger.rs
index 3bcb1ae37..14887c5cc 100644
--- a/crates/rust-analyzer/src/bin/logger.rs
+++ b/crates/rust-analyzer/src/bin/logger.rs
@@ -4,7 +4,7 @@
 
 use std::{
     fs::File,
-    io::{BufWriter, Write},
+    io::{self, BufWriter, Write},
 };
 
 use env_logger::filter::{Builder, Filter};
@@ -14,10 +14,11 @@ use parking_lot::Mutex;
 pub(crate) struct Logger {
     filter: Filter,
     file: Option<Mutex<BufWriter<File>>>,
+    no_buffering: bool,
 }
 
 impl Logger {
-    pub(crate) fn new(log_file: Option<File>, filter: Option<&str>) -> Logger {
+    pub(crate) fn new(log_file: Option<File>, no_buffering: bool, filter: Option<&str>) -> Logger {
         let filter = {
             let mut builder = Builder::new();
             if let Some(filter) = filter {
@@ -28,7 +29,7 @@ impl Logger {
 
         let file = log_file.map(|it| Mutex::new(BufWriter::new(it)));
 
-        Logger { filter, file }
+        Logger { filter, file, no_buffering }
     }
 
     pub(crate) fn install(self) {
@@ -46,7 +47,8 @@ impl Log for Logger {
         if !self.filter.matches(record) {
             return;
         }
-        match &self.file {
+
+        let should_flush = match &self.file {
             Some(w) => {
                 let _ = writeln!(
                     w.lock(),
@@ -55,19 +57,32 @@ impl Log for Logger {
                     record.module_path().unwrap_or_default(),
                     record.args(),
                 );
+                self.no_buffering
+            }
+            None => {
+                eprintln!(
+                    "[{} {}] {}",
+                    record.level(),
+                    record.module_path().unwrap_or_default(),
+                    record.args(),
+                );
+                true // flush stderr unconditionally
             }
-            None => eprintln!(
-                "[{} {}] {}",
-                record.level(),
-                record.module_path().unwrap_or_default(),
-                record.args(),
-            ),
+        };
+
+        if should_flush {
+            self.flush();
         }
     }
 
     fn flush(&self) {
-        if let Some(w) = &self.file {
-            let _ = w.lock().flush();
+        match &self.file {
+            Some(w) => {
+                let _ = w.lock().flush();
+            }
+            None => {
+                let _ = io::stderr().flush();
+            }
         }
     }
 }