refactor(npm): improve locking around updating npm resolution (#24104)

Introduces a `SyncReadAsyncWriteLock` to make it harder to write to the
npm resolution without first waiting async in a queue. For the npm
resolution, reading synchronously is fine, but when updating, someone
should wait async, clone the data, then write the data at the end back.

6 files changed, 345 insertions, 45 deletions

diff --git a/cli/util/sync/async_flag.rs b/cli/util/sync/async_flag.rs
new file mode 100644
index 000000000..2bdff63c0
--- /dev/null
+++ b/cli/util/sync/async_flag.rs
@@ -0,0 +1,20 @@
+// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
+
+use tokio_util::sync::CancellationToken;
+
+#[derive(Debug, Default, Clone)]
+pub struct AsyncFlag(CancellationToken);
+
+impl AsyncFlag {
+  pub fn raise(&self) {
+    self.0.cancel();
+  }
+
+  pub fn is_raised(&self) -> bool {
+    self.0.is_cancelled()
+  }
+
+  pub fn wait_raised(&self) -> impl std::future::Future<Output = ()> + '_ {
+    self.0.cancelled()
+  }
+}
diff --git a/cli/util/sync/atomic_flag.rs b/cli/util/sync/atomic_flag.rs
new file mode 100644
index 000000000..75396dcf4
--- /dev/null
+++ b/cli/util/sync/atomic_flag.rs
@@ -0,0 +1,35 @@
+// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
+
+use std::sync::atomic::AtomicBool;
+use std::sync::atomic::Ordering;
+
+/// Simplifies the use of an atomic boolean as a flag.
+#[derive(Debug, Default)]
+pub struct AtomicFlag(AtomicBool);
+
+impl AtomicFlag {
+  /// Raises the flag returning if the raise was successful.
+  pub fn raise(&self) -> bool {
+    !self.0.swap(true, Ordering::SeqCst)
+  }
+
+  /// Gets if the flag is raised.
+  pub fn is_raised(&self) -> bool {
+    self.0.load(Ordering::SeqCst)
+  }
+}
+
+#[cfg(test)]
+mod test {
+  use super::*;
+
+  #[test]
+  fn atomic_flag_raises() {
+    let flag = AtomicFlag::default();
+    assert!(!flag.is_raised()); // false by default
+    assert!(flag.raise());
+    assert!(flag.is_raised());
+    assert!(!flag.raise());
+    assert!(flag.is_raised());
+  }
+}
diff --git a/cli/util/sync/mod.rs b/cli/util/sync/mod.rs
new file mode 100644
index 000000000..28aab7f47
--- /dev/null
+++ b/cli/util/sync/mod.rs
@@ -0,0 +1,14 @@
+// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
+
+mod async_flag;
+mod atomic_flag;
+mod sync_read_async_write_lock;
+mod task_queue;
+mod value_creator;
+
+pub use async_flag::AsyncFlag;
+pub use atomic_flag::AtomicFlag;
+pub use sync_read_async_write_lock::SyncReadAsyncWriteLock;
+pub use task_queue::TaskQueue;
+pub use task_queue::TaskQueuePermit;
+pub use value_creator::MultiRuntimeAsyncValueCreator;
diff --git a/cli/util/sync/sync_read_async_write_lock.rs b/cli/util/sync/sync_read_async_write_lock.rs
new file mode 100644
index 000000000..8bd211aa7
--- /dev/null
+++ b/cli/util/sync/sync_read_async_write_lock.rs
@@ -0,0 +1,62 @@
+// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
+
+use deno_core::parking_lot::RwLock;
+use deno_core::parking_lot::RwLockReadGuard;
+use deno_core::parking_lot::RwLockWriteGuard;
+
+use super::TaskQueue;
+use super::TaskQueuePermit;
+
+/// A lock that can be read synchronously at any time (including when
+/// being written to), but must write asynchronously.
+pub struct SyncReadAsyncWriteLockWriteGuard<'a, T: Send + Sync> {
+  _update_permit: TaskQueuePermit<'a>,
+  data: &'a RwLock<T>,
+}
+
+impl<'a, T: Send + Sync> SyncReadAsyncWriteLockWriteGuard<'a, T> {
+  pub fn read(&self) -> RwLockReadGuard<'_, T> {
+    self.data.read()
+  }
+
+  /// Warning: Only `write()` with data you created within this
+  /// write this `SyncReadAsyncWriteLockWriteGuard`.
+  ///
+  /// ```rs
+  /// let mut data = lock.write().await;
+  ///
+  /// let mut data = data.read().clone();
+  /// data.value = 2;
+  /// *data.write() = data;
+  /// ```
+  pub fn write(&self) -> RwLockWriteGuard<'_, T> {
+    self.data.write()
+  }
+}
+
+/// A lock that can only be
+pub struct SyncReadAsyncWriteLock<T: Send + Sync> {
+  data: RwLock<T>,
+  update_queue: TaskQueue,
+}
+
+impl<T: Send + Sync> SyncReadAsyncWriteLock<T> {
+  pub fn new(data: T) -> Self {
+    Self {
+      data: RwLock::new(data),
+      update_queue: TaskQueue::default(),
+    }
+  }
+
+  pub fn read(&self) -> RwLockReadGuard<'_, T> {
+    self.data.read()
+  }
+
+  pub async fn acquire(&self) -> SyncReadAsyncWriteLockWriteGuard<'_, T> {
+    let update_permit = self.update_queue.acquire().await;
+    SyncReadAsyncWriteLockWriteGuard {
+      _update_permit: update_permit,
+      data: &self.data,
+    }
+  }
+}
diff --git a/cli/util/sync.rs b/cli/util/sync/task_queue.rs
index 3986c883e..6ef747e1a 100644
--- a/cli/util/sync.rs
+++ b/cli/util/sync/task_queue.rs
@@ -1,30 +1,13 @@
 // Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
 
 use std::collections::LinkedList;
-use std::sync::atomic::AtomicBool;
-use std::sync::atomic::Ordering;
 use std::sync::Arc;
 
 use deno_core::futures::task::AtomicWaker;
 use deno_core::futures::Future;
 use deno_core::parking_lot::Mutex;
-use tokio_util::sync::CancellationToken;
 
-/// Simplifies the use of an atomic boolean as a flag.
-#[derive(Debug, Default)]
-pub struct AtomicFlag(AtomicBool);
-
-impl AtomicFlag {
-  /// Raises the flag returning if the raise was successful.
-  pub fn raise(&self) -> bool {
-    !self.0.swap(true, Ordering::SeqCst)
-  }
-
-  /// Gets if the flag is raised.
-  pub fn is_raised(&self) -> bool {
-    self.0.load(Ordering::SeqCst)
-  }
-}
+use super::AtomicFlag;
 
 #[derive(Debug, Default)]
 struct TaskQueueTaskItem {
@@ -161,23 +144,6 @@ impl<'a> Future for TaskQueuePermitAcquireFuture<'a> {
   }
 }
 
-#[derive(Debug, Default, Clone)]
-pub struct AsyncFlag(CancellationToken);
-
-impl AsyncFlag {
-  pub fn raise(&self) {
-    self.0.cancel();
-  }
-
-  pub fn is_raised(&self) -> bool {
-    self.0.is_cancelled()
-  }
-
-  pub fn wait_raised(&self) -> impl std::future::Future<Output = ()> + '_ {
-    self.0.cancelled()
-  }
-}
-
 #[cfg(test)]
 mod test {
   use deno_core::futures;
@@ -186,16 +152,6 @@ mod test {
 
   use super::*;
 
-  #[test]
-  fn atomic_flag_raises() {
-    let flag = AtomicFlag::default();
-    assert!(!flag.is_raised()); // false by default
-    assert!(flag.raise());
-    assert!(flag.is_raised());
-    assert!(!flag.raise());
-    assert!(flag.is_raised());
-  }
-
   #[tokio::test]
   async fn task_queue_runs_one_after_other() {
     let task_queue = TaskQueue::default();
diff --git a/cli/util/sync/value_creator.rs b/cli/util/sync/value_creator.rs
new file mode 100644
index 000000000..57aabe801
--- /dev/null
+++ b/cli/util/sync/value_creator.rs
@@ -0,0 +1,213 @@
+// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
+
+use std::sync::Arc;
+
+use deno_core::futures::future::BoxFuture;
+use deno_core::futures::future::LocalBoxFuture;
+use deno_core::futures::future::Shared;
+use deno_core::futures::FutureExt;
+use deno_core::parking_lot::Mutex;
+use tokio::task::JoinError;
+
+type JoinResult<TResult> = Result<TResult, Arc<JoinError>>;
+type CreateFutureFn<TResult> =
+  Box<dyn Fn() -> LocalBoxFuture<'static, TResult> + Send + Sync>;
+
+#[derive(Debug)]
+struct State<TResult> {
+  retry_index: usize,
+  future: Option<Shared<BoxFuture<'static, JoinResult<TResult>>>>,
+}
+
+/// Attempts to create a shared value asynchronously on one tokio runtime while
+/// many runtimes are requesting the value.
+///
+/// This is only useful when the value needs to get created once across
+/// many runtimes.
+///
+/// This handles the case where the tokio runtime creating the value goes down
+/// while another one is waiting on the value.
+pub struct MultiRuntimeAsyncValueCreator<TResult: Send + Clone + 'static> {
+  create_future: CreateFutureFn<TResult>,
+  state: Mutex<State<TResult>>,
+}
+
+impl<TResult: Send + Clone + 'static> std::fmt::Debug
+  for MultiRuntimeAsyncValueCreator<TResult>
+{
+  fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+    f.debug_struct("MultiRuntimeAsyncValueCreator").finish()
+  }
+}
+
+impl<TResult: Send + Clone + 'static> MultiRuntimeAsyncValueCreator<TResult> {
+  pub fn new(create_future: CreateFutureFn<TResult>) -> Self {
+    Self {
+      state: Mutex::new(State {
+        retry_index: 0,
+        future: None,
+      }),
+      create_future,
+    }
+  }
+
+  pub async fn get(&self) -> TResult {
+    let (mut future, mut retry_index) = {
+      let mut state = self.state.lock();
+      let future = match &state.future {
+        Some(future) => future.clone(),
+        None => {
+          let future = self.create_shared_future();
+          state.future = Some(future.clone());
+          future
+        }
+      };
+      (future, state.retry_index)
+    };
+
+    loop {
+      let result = future.await;
+
+      match result {
+        Ok(result) => return result,
+        Err(join_error) => {
+          if join_error.is_cancelled() {
+            let mut state = self.state.lock();
+
+            if state.retry_index == retry_index {
+              // we were the first one to retry, so create a new future
+              // that we'll run from the current runtime
+              state.retry_index += 1;
+              state.future = Some(self.create_shared_future());
+            }
+
+            retry_index = state.retry_index;
+            future = state.future.as_ref().unwrap().clone();
+
+            // just in case we're stuck in a loop
+            if retry_index > 1000 {
+              panic!("Something went wrong.") // should never happen
+            }
+          } else {
+            panic!("{}", join_error);
+          }
+        }
+      }
+    }
+  }
+
+  fn create_shared_future(
+    &self,
+  ) -> Shared<BoxFuture<'static, JoinResult<TResult>>> {
+    let future = (self.create_future)();
+    deno_core::unsync::spawn(future)
+      .map(|result| result.map_err(Arc::new))
+      .boxed()
+      .shared()
+  }
+}
+
+#[cfg(test)]
+mod test {
+  use deno_core::unsync::spawn;
+
+  use super::*;
+
+  #[tokio::test]
+  async fn single_runtime() {
+    let value_creator = MultiRuntimeAsyncValueCreator::new(Box::new(|| {
+      async { 1 }.boxed_local()
+    }));
+    let value = value_creator.get().await;
+    assert_eq!(value, 1);
+  }
+
+  #[test]
+  fn multi_runtimes() {
+    let value_creator =
+      Arc::new(MultiRuntimeAsyncValueCreator::new(Box::new(|| {
+        async {
+          tokio::task::yield_now().await;
+          1
+        }
+        .boxed_local()
+      })));
+    let handles = (0..3)
+      .map(|_| {
+        let value_creator = value_creator.clone();
+        std::thread::spawn(|| {
+          create_runtime().block_on(async move { value_creator.get().await })
+        })
+      })
+      .collect::<Vec<_>>();
+    for handle in handles {
+      assert_eq!(handle.join().unwrap(), 1);
+    }
+  }
+
+  #[test]
+  fn multi_runtimes_first_never_finishes() {
+    let is_first_run = Arc::new(Mutex::new(true));
+    let (tx, rx) = std::sync::mpsc::channel::<()>();
+    let value_creator = Arc::new(MultiRuntimeAsyncValueCreator::new({
+      let is_first_run = is_first_run.clone();
+      Box::new(move || {
+        let is_first_run = is_first_run.clone();
+        let tx = tx.clone();
+        async move {
+          let is_first_run = {
+            let mut is_first_run = is_first_run.lock();
+            let initial_value = *is_first_run;
+            *is_first_run = false;
+            tx.send(()).unwrap();
+            initial_value
+          };
+          if is_first_run {
+            tokio::time::sleep(std::time::Duration::from_millis(30_000)).await;
+            panic!("TIMED OUT"); // should not happen
+          } else {
+            tokio::task::yield_now().await;
+          }
+          1
+        }
+        .boxed_local()
+      })
+    }));
+    std::thread::spawn({
+      let value_creator = value_creator.clone();
+      let is_first_run = is_first_run.clone();
+      move || {
+        create_runtime().block_on(async {
+          let value_creator = value_creator.clone();
+          // spawn a task that will never complete
+          spawn(async move { value_creator.get().await });
+          // wait for the task to set is_first_run to false
+          while *is_first_run.lock() {
+            tokio::time::sleep(std::time::Duration::from_millis(20)).await;
+          }
+          // now exit the runtime while the value_creator is still pending
+        })
+      }
+    });
+    let handle = {
+      let value_creator = value_creator.clone();
+      std::thread::spawn(|| {
+        create_runtime().block_on(async move {
+          let value_creator = value_creator.clone();
+          rx.recv().unwrap();
+          // even though the other runtime shutdown, this get() should
+          // recover and still get the value
+          value_creator.get().await
+        })
+      })
+    };
+    assert_eq!(handle.join().unwrap(), 1);
+  }
+
+  fn create_runtime() -> tokio::runtime::Runtime {
+    tokio::runtime::Builder::new_current_thread()
+      .enable_all()
+      .build()
+      .unwrap()
+  }
+}