From d79f21c29fb2753245ca09d9a5b74332f5dcfe4f Mon Sep 17 00:00:00 2001
From: Benjamin Woodruff <benjamin.woodruff@vercel.com>
Date: Wed, 8 Jan 2025 16:48:40 -0800
Subject: [PATCH] refactor(turbo-tasks): Add common traits (TaskInput,
 NonLocalValue, etc) to `either::Either<L, R>` (#74198)

I ended up abandoning https://github.com/vercel/next.js/pull/74108, but the `Either` trait implementations in there seemed nice-to-have, so I'm publishing them here instead.
---
 Cargo.lock                                    |  1 +
 turbopack/crates/turbo-tasks/Cargo.toml       |  1 +
 .../crates/turbo-tasks/src/marker_trait.rs    |  1 +
 .../crates/turbo-tasks/src/task/task_input.rs | 24 +++++++++++++++++++
 turbopack/crates/turbo-tasks/src/trace.rs     | 10 ++++++++
 5 files changed, 37 insertions(+)

diff --git a/Cargo.lock b/Cargo.lock
index 27c7e2581df6b..fe647084ac96d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -8420,6 +8420,7 @@ dependencies = [
  "auto-hash-map",
  "concurrent-queue",
  "dashmap 6.1.0",
+ "either",
  "erased-serde",
  "event-listener 2.5.3",
  "futures",
diff --git a/turbopack/crates/turbo-tasks/Cargo.toml b/turbopack/crates/turbo-tasks/Cargo.toml
index 2d5ec14702983..fb521d5fb645c 100644
--- a/turbopack/crates/turbo-tasks/Cargo.toml
+++ b/turbopack/crates/turbo-tasks/Cargo.toml
@@ -22,6 +22,7 @@ async-trait = { workspace = true }
 auto-hash-map = { workspace = true }
 concurrent-queue = { workspace = true }
 dashmap = { workspace = true }
+either = { workspace = true }
 erased-serde = "0.3.20"
 event-listener = "2.5.3"
 futures = { workspace = true }
diff --git a/turbopack/crates/turbo-tasks/src/marker_trait.rs b/turbopack/crates/turbo-tasks/src/marker_trait.rs
index eaf5e5d8f293f..96bbe78e618f2 100644
--- a/turbopack/crates/turbo-tasks/src/marker_trait.rs
+++ b/turbopack/crates/turbo-tasks/src/marker_trait.rs
@@ -66,6 +66,7 @@ macro_rules! impl_auto_marker_trait {
         unsafe impl<T: $trait + ?Sized> $trait for ::std::sync::Mutex<T> {}
         unsafe impl<T: $trait + ?Sized> $trait for ::std::cell::RefCell<T> {}
         unsafe impl<T: ?Sized> $trait for ::std::marker::PhantomData<T> {}
+        unsafe impl<L: $trait, R: $trait> $trait for ::either::Either<L, R> {}
 
         unsafe impl<T: $trait + ?Sized> $trait for $crate::TraitRef<T> {}
         unsafe impl<T> $trait for $crate::ReadRef<T>
diff --git a/turbopack/crates/turbo-tasks/src/task/task_input.rs b/turbopack/crates/turbo-tasks/src/task/task_input.rs
index bb30ca6341c0a..82cca75349343 100644
--- a/turbopack/crates/turbo-tasks/src/task/task_input.rs
+++ b/turbopack/crates/turbo-tasks/src/task/task_input.rs
@@ -1,6 +1,7 @@
 use std::{any::Any, fmt::Debug, future::Future, hash::Hash, time::Duration};
 
 use anyhow::Result;
+use either::Either;
 use serde::{Deserialize, Serialize};
 use turbo_rcstr::RcStr;
 
@@ -220,6 +221,29 @@ impl<'de, T> Deserialize<'de> for TransientInstance<T> {
     }
 }
 
+impl<L, R> TaskInput for Either<L, R>
+where
+    L: TaskInput,
+    R: TaskInput,
+{
+    fn resolve(&self) -> impl Future<Output = Result<Self>> + Send + '_ {
+        self.as_ref().map_either(
+            |l| async move { anyhow::Ok(Either::Left(l.resolve().await?)) },
+            |r| async move { anyhow::Ok(Either::Right(r.resolve().await?)) },
+        )
+    }
+
+    fn is_resolved(&self) -> bool {
+        self.as_ref()
+            .either(TaskInput::is_resolved, TaskInput::is_resolved)
+    }
+
+    fn is_transient(&self) -> bool {
+        self.as_ref()
+            .either(TaskInput::is_transient, TaskInput::is_transient)
+    }
+}
+
 macro_rules! tuple_impls {
     ( $( $name:ident )+ ) => {
         impl<$($name: TaskInput),+> TaskInput for ($($name,)+)
diff --git a/turbopack/crates/turbo-tasks/src/trace.rs b/turbopack/crates/turbo-tasks/src/trace.rs
index 01c6704e708df..0621fcf6696cc 100644
--- a/turbopack/crates/turbo-tasks/src/trace.rs
+++ b/turbopack/crates/turbo-tasks/src/trace.rs
@@ -9,6 +9,7 @@ use std::{
 };
 
 use auto_hash_map::{AutoMap, AutoSet};
+use either::Either;
 use indexmap::{IndexMap, IndexSet};
 use turbo_rcstr::RcStr;
 
@@ -253,4 +254,13 @@ impl<T: TraceRawVcs + ?Sized> TraceRawVcs for &mut T {
     }
 }
 
+impl<L: TraceRawVcs, R: TraceRawVcs> TraceRawVcs for Either<L, R> {
+    fn trace_raw_vcs(&self, trace_context: &mut TraceRawVcsContext) {
+        match self {
+            Either::Left(l) => l.trace_raw_vcs(trace_context),
+            Either::Right(r) => r.trace_raw_vcs(trace_context),
+        }
+    }
+}
+
 pub use turbo_tasks_macros::TraceRawVcs;