perf(cache): compile ts to js in parallel for deno cache (#23892)

Closes https://github.com/denoland/deno/issues/23860

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;
@@ -48,9 +51,12 @@ 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 Module::Js(module) = module else {
+        continue;
+      };
+
       let is_emittable = matches!(
         module.media_type,
         MediaType::TypeScript
@@ -60,16 +66,22 @@ impl Emitter {
           | 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(())
   }