From c89f9f9ad1e3d940a460092ee7bc44eb046fa1e1 Mon Sep 17 00:00:00 2001
From: David Sherret <dsherret@users.noreply.github.com>
Date: Mon, 20 May 2024 13:49:12 -0400
Subject: [PATCH] perf(cache): compile ts to js in parallel for `deno cache`
 (#23892)

Closes https://github.com/denoland/deno/issues/23860
---
 cli/emit.rs | 38 +++++++++++++++++++++++++-------------
 1 file changed, 25 insertions(+), 13 deletions(-)

diff --git a/cli/emit.rs b/cli/emit.rs
index a3352e01f8..2106442262 100644
--- a/cli/emit.rs
+++ b/cli/emit.rs
@@ -7,6 +7,9 @@ use crate::cache::ParsedSourceCache;
 use deno_ast::SourceMapOption;
 use deno_ast::TranspileResult;
 use deno_core::error::AnyError;
+use deno_core::futures::stream::FuturesUnordered;
+use deno_core::futures::FutureExt;
+use deno_core::futures::StreamExt;
 use deno_core::ModuleCodeString;
 use deno_core::ModuleSpecifier;
 use deno_graph::MediaType;
@@ -48,28 +51,37 @@ impl Emitter {
     &self,
     graph: &ModuleGraph,
   ) -> Result<(), AnyError> {
-    // todo(dsherret): we could do this concurrently
+    let mut futures = FuturesUnordered::new();
     for module in graph.modules() {
-      if let Module::Js(module) = module {
-        let is_emittable = matches!(
-          module.media_type,
-          MediaType::TypeScript
-            | MediaType::Mts
-            | MediaType::Cts
-            | MediaType::Jsx
-            | MediaType::Tsx
-        );
-        if is_emittable {
+      let Module::Js(module) = module else {
+        continue;
+      };
+
+      let is_emittable = matches!(
+        module.media_type,
+        MediaType::TypeScript
+          | MediaType::Mts
+          | MediaType::Cts
+          | MediaType::Jsx
+          | MediaType::Tsx
+      );
+      if is_emittable {
+        futures.push(
           self
             .emit_parsed_source(
               &module.specifier,
               module.media_type,
               &module.source,
             )
-            .await?;
-        }
+            .boxed_local(),
+        );
       }
     }
+
+    while let Some(result) = futures.next().await {
+      result?; // surface errors
+    }
+
     Ok(())
   }