From adc8d4e1e70b9e252caa0bc6ba729fa3c0ef4dbd Mon Sep 17 00:00:00 2001
From: Micha Reiser <micha@reiser.io>
Date: Tue, 30 Jul 2024 19:18:43 +0200
Subject: [PATCH] File watch events: Add dynamic wait period before writing new
 changes (#12585)

---
 Cargo.lock                             |  1 +
 crates/red_knot/Cargo.toml             |  1 +
 crates/red_knot/tests/file_watching.rs | 23 ++++++++++++++++++-----
 3 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/Cargo.lock b/Cargo.lock
index dc612cfa77..e4b3156f04 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1944,6 +1944,7 @@ dependencies = [
  "countme",
  "crossbeam",
  "ctrlc",
+ "filetime",
  "notify",
  "rayon",
  "red_knot_module_resolver",
diff --git a/crates/red_knot/Cargo.toml b/crates/red_knot/Cargo.toml
index a4c6166d60..5434852061 100644
--- a/crates/red_knot/Cargo.toml
+++ b/crates/red_knot/Cargo.toml
@@ -27,6 +27,7 @@ notify = { workspace = true }
 rayon = { workspace = true }
 rustc-hash = { workspace = true }
 salsa = { workspace = true }
+filetime = { workspace = true }
 tracing = { workspace = true }
 tracing-subscriber = { workspace = true }
 tracing-tree = { workspace = true }
diff --git a/crates/red_knot/tests/file_watching.rs b/crates/red_knot/tests/file_watching.rs
index 3f3db3b6e5..1396c56c2b 100644
--- a/crates/red_knot/tests/file_watching.rs
+++ b/crates/red_knot/tests/file_watching.rs
@@ -3,6 +3,7 @@
 use std::time::Duration;
 
 use anyhow::{anyhow, Context};
+use filetime::FileTime;
 use salsa::Setter;
 
 use red_knot::db::RootDatabase;
@@ -184,12 +185,24 @@ where
 }
 
 /// The precision of the last modified time is platform dependent and not arbitrarily precise.
-/// This method sets the current thread to sleep for a duration that
-/// is larger than the [last-modified precision on all platforms](https://doc.rust-lang.org/nightly/std/time/struct.SystemTime.html#platform-specific-behavior).
-///
-/// Calling the function is only necessary when making changes to an **existing** file.
+/// This method sleeps until the last modified time of a newly created file changes. This guarantees
+/// that the last modified time of any file written **after** this method completes should be different.
 fn next_io_tick() {
-    std::thread::sleep(Duration::from_nanos(200));
+    let temp = tempfile::tempfile().unwrap();
+
+    let last_modified = FileTime::from_last_modification_time(&temp.metadata().unwrap());
+
+    loop {
+        filetime::set_file_handle_times(&temp, None, Some(FileTime::now())).unwrap();
+
+        let new_last_modified = FileTime::from_last_modification_time(&temp.metadata().unwrap());
+
+        if new_last_modified != last_modified {
+            break;
+        }
+
+        std::thread::sleep(Duration::from_nanos(100));
+    }
 }
 
 #[test]