From 1cc60d30cbc5dda59a3e012fcbf0c65c267ab2bd Mon Sep 17 00:00:00 2001
From: thebriando <bdo@atlassian.com>
Date: Fri, 2 Sep 2022 11:35:53 -0700
Subject: [PATCH 01/12] Package on main thread when there's only one bundle in
 request

---
 packages/core/core/src/PackagerRunner.js      |  2 ++
 packages/core/core/src/ReporterRunner.js      | 10 ++++----
 .../core/core/src/requests/PackageRequest.js  |  6 +++--
 .../core/src/requests/WriteBundlesRequest.js  | 24 +++++++++++++++----
 packages/core/core/src/worker.js              |  7 ++++--
 packages/core/types/index.js                  |  2 ++
 6 files changed, 38 insertions(+), 13 deletions(-)

diff --git a/packages/core/core/src/PackagerRunner.js b/packages/core/core/src/PackagerRunner.js
index 3c18a16c10b..a82e023c1e5 100644
--- a/packages/core/core/src/PackagerRunner.js
+++ b/packages/core/core/src/PackagerRunner.js
@@ -325,6 +325,7 @@ export default class PackagerRunner {
       type: 'buildProgress',
       phase: 'packaging',
       bundle,
+      bundleGraph,
     });
 
     let packager = await this.config.getPackager(bundle.name);
@@ -418,6 +419,7 @@ export default class PackagerRunner {
       type: 'buildProgress',
       phase: 'optimizing',
       bundle,
+      bundleGraph: internalBundleGraph,
     });
 
     let optimized = {
diff --git a/packages/core/core/src/ReporterRunner.js b/packages/core/core/src/ReporterRunner.js
index 9b07912bb7e..535dcddc1dd 100644
--- a/packages/core/core/src/ReporterRunner.js
+++ b/packages/core/core/src/ReporterRunner.js
@@ -64,10 +64,12 @@ export default class ReporterRunner {
       let bundle: InternalBundle = event.bundle;
       // Convert any internal bundles back to their public equivalents as reporting
       // is public api
-      let bundleGraph = this.workerFarm.workerApi.getSharedReference(
-        // $FlowFixMe
-        bundleGraphRef,
-      );
+      let bundleGraph =
+        event.bundleGraph ??
+        this.workerFarm.workerApi.getSharedReference(
+          // $FlowFixMe
+          bundleGraphRef,
+        );
       invariant(bundleGraph instanceof BundleGraph);
       // $FlowFixMe[incompatible-call]
       this.report({
diff --git a/packages/core/core/src/requests/PackageRequest.js b/packages/core/core/src/requests/PackageRequest.js
index e02c605fd30..33c4a967071 100644
--- a/packages/core/core/src/requests/PackageRequest.js
+++ b/packages/core/core/src/requests/PackageRequest.js
@@ -18,7 +18,7 @@ import createParcelConfigRequest from './ParcelConfigRequest';
 type PackageRequestInput = {|
   bundleGraph: BundleGraph,
   bundle: Bundle,
-  bundleGraphReference: SharedReference,
+  bundleGraphReference?: SharedReference,
   optionsRef: SharedReference,
 |};
 
@@ -54,10 +54,12 @@ async function run({input, api, farm}: RunInput) {
   let {cachePath} = nullthrows(
     await api.runRequest<null, ConfigAndCachePath>(createParcelConfigRequest()),
   );
+
   let {devDepRequests, configRequests, bundleInfo, invalidations} =
     await runPackage({
       bundle,
-      bundleGraphReference,
+      bundleGraphReference:
+        bundleGraphReference == null ? input.bundleGraph : bundleGraphReference,
       optionsRef,
       configCachePath: cachePath,
       previousDevDeps: devDeps,
diff --git a/packages/core/core/src/requests/WriteBundlesRequest.js b/packages/core/core/src/requests/WriteBundlesRequest.js
index bdfcbcf1360..870fbd3507c 100644
--- a/packages/core/core/src/requests/WriteBundlesRequest.js
+++ b/packages/core/core/src/requests/WriteBundlesRequest.js
@@ -49,10 +49,6 @@ export default function createWriteBundlesRequest(
 
 async function run({input, api, farm, options}: RunInput) {
   let {bundleGraph, optionsRef} = input;
-  let {ref, dispose} = await farm.createSharedReference(
-    bundleGraph,
-    serialize(bundleGraph),
-  );
 
   api.invalidateOnOptionChange('shouldContentHash');
 
@@ -80,9 +76,25 @@ async function run({input, api, farm, options}: RunInput) {
       return false;
     }
 
+    // Filter out skippable requests.
+    // if (api.canSkipSubrequest(bundleGraph.getHash(bundle))) {
+    //   // console.log('skipping', bundle.id);
+    //   return false;
+    // }
+
     return true;
   });
 
+  let ref;
+  let dispose;
+
+  // Create shared reference in WorkerFarm if we need to change multiple bundles.
+  if (bundles.length > 1) {
+    ({ref, dispose} = await farm.createSharedReference(
+      bundleGraph,
+      serialize(bundleGraph),
+    ));
+  }
   try {
     await Promise.all(
       bundles.map(async bundle => {
@@ -133,7 +145,9 @@ async function run({input, api, farm, options}: RunInput) {
     api.storeResult(res);
     return res;
   } finally {
-    await dispose();
+    if (dispose) {
+      await dispose();
+    }
   }
 }
 
diff --git a/packages/core/core/src/worker.js b/packages/core/core/src/worker.js
index bb1467076f5..22da7b05041 100644
--- a/packages/core/core/src/worker.js
+++ b/packages/core/core/src/worker.js
@@ -121,7 +121,7 @@ export async function runPackage(
     previousInvalidations,
   }: {|
     bundle: Bundle,
-    bundleGraphReference: SharedReference,
+    bundleGraphReference: SharedReference | BundleGraph,
     configCachePath: string,
     optionsRef: SharedReference,
     previousDevDeps: Map<string, string>,
@@ -129,7 +129,10 @@ export async function runPackage(
     previousInvalidations: Array<RequestInvalidation>,
   |},
 ): Promise<PackageRequestResult> {
-  let bundleGraph = workerApi.getSharedReference(bundleGraphReference);
+  let bundleGraph =
+    typeof bundleGraphReference === 'number'
+      ? workerApi.getSharedReference(bundleGraphReference)
+      : bundleGraphReference;
   invariant(bundleGraph instanceof BundleGraph);
   let options = loadOptions(optionsRef, workerApi);
   let parcelConfig = await loadConfig(configCachePath, options);
diff --git a/packages/core/types/index.js b/packages/core/types/index.js
index 2c1ca94685e..a57400f8089 100644
--- a/packages/core/types/index.js
+++ b/packages/core/types/index.js
@@ -1750,6 +1750,7 @@ export type PackagingProgressEvent = {|
   +type: 'buildProgress',
   +phase: 'packaging',
   +bundle: NamedBundle,
+  +bundleGraph?: BundleGraph<NamedBundle>,
 |};
 
 /**
@@ -1760,6 +1761,7 @@ export type OptimizingProgressEvent = {|
   +type: 'buildProgress',
   +phase: 'optimizing',
   +bundle: NamedBundle,
+  +bundleGraph?: BundleGraph<NamedBundle>,
 |};
 
 /**

From 43847dda032c280d8795b709d3c4f6be5bc1e917 Mon Sep 17 00:00:00 2001
From: thebriando <bdo@atlassian.com>
Date: Fri, 2 Sep 2022 13:16:55 -0700
Subject: [PATCH 02/12] Fix flow errors

---
 packages/core/types/index.js | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/packages/core/types/index.js b/packages/core/types/index.js
index 076e72b1c48..f1bf04575e8 100644
--- a/packages/core/types/index.js
+++ b/packages/core/types/index.js
@@ -5,6 +5,7 @@ import type SourceMap from '@parcel/source-map';
 import type {FileSystem} from '@parcel/fs';
 import type WorkerFarm from '@parcel/workers';
 import type {PackageManager} from '@parcel/package-manager';
+import type InternalBundleGraph from '../core/src/BundleGraph';
 import type {
   Diagnostic,
   Diagnostifiable,
@@ -1754,7 +1755,7 @@ export type PackagingProgressEvent = {|
   +type: 'buildProgress',
   +phase: 'packaging',
   +bundle: NamedBundle,
-  +bundleGraph?: BundleGraph<NamedBundle>,
+  +bundleGraph?: InternalBundleGraph,
 |};
 
 /**
@@ -1765,7 +1766,7 @@ export type OptimizingProgressEvent = {|
   +type: 'buildProgress',
   +phase: 'optimizing',
   +bundle: NamedBundle,
-  +bundleGraph?: BundleGraph<NamedBundle>,
+  +bundleGraph?: InternalBundleGraph,
 |};
 
 /**

From ad39a493fc99fd68dab059fa115d368edad2d973 Mon Sep 17 00:00:00 2001
From: thebriando <bdo@atlassian.com>
Date: Fri, 9 Sep 2022 12:01:11 -0700
Subject: [PATCH 03/12] Use report instead of reportWorker when not farming out

---
 packages/core/core/src/PackagerRunner.js |  8 ++++++--
 packages/core/core/src/ReporterRunner.js | 14 +++++++++++++-
 packages/core/core/src/worker.js         |  8 ++++++--
 3 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/packages/core/core/src/PackagerRunner.js b/packages/core/core/src/PackagerRunner.js
index a82e023c1e5..2b2bd5b89d7 100644
--- a/packages/core/core/src/PackagerRunner.js
+++ b/packages/core/core/src/PackagerRunner.js
@@ -67,6 +67,7 @@ type Opts = {|
   report: ReportFn,
   previousDevDeps: Map<string, string>,
   previousInvalidations: Array<RequestInvalidation>,
+  useFarm: boolean,
 |};
 
 export type PackageRequestResult = {|
@@ -109,6 +110,7 @@ export default class PackagerRunner {
   devDepRequests: Map<string, DevDepRequest>;
   invalidations: Map<string, RequestInvalidation>;
   previousInvalidations: Array<RequestInvalidation>;
+  useFarm: boolean;
 
   constructor({
     config,
@@ -116,6 +118,7 @@ export default class PackagerRunner {
     report,
     previousDevDeps,
     previousInvalidations,
+    useFarm,
   }: Opts) {
     this.config = config;
     this.options = options;
@@ -123,6 +126,7 @@ export default class PackagerRunner {
     this.previousDevDeps = previousDevDeps;
     this.devDepRequests = new Map();
     this.previousInvalidations = previousInvalidations;
+    this.useFarm = useFarm;
     this.invalidations = new Map();
     this.pluginOptions = new PluginOptions(
       optionsProxy(this.options, option => {
@@ -325,7 +329,7 @@ export default class PackagerRunner {
       type: 'buildProgress',
       phase: 'packaging',
       bundle,
-      bundleGraph,
+      bundleGraph: this.useFarm ? undefined : bundleGraph,
     });
 
     let packager = await this.config.getPackager(bundle.name);
@@ -419,7 +423,7 @@ export default class PackagerRunner {
       type: 'buildProgress',
       phase: 'optimizing',
       bundle,
-      bundleGraph: internalBundleGraph,
+      bundleGraph: this.useFarm ? undefined : internalBundleGraph,
     });
 
     let optimized = {
diff --git a/packages/core/core/src/ReporterRunner.js b/packages/core/core/src/ReporterRunner.js
index 535dcddc1dd..6b358871343 100644
--- a/packages/core/core/src/ReporterRunner.js
+++ b/packages/core/core/src/ReporterRunner.js
@@ -133,5 +133,17 @@ export function reportWorker(workerApi: WorkerApi, event: ReporterEvent) {
 }
 
 export function report(event: ReporterEvent) {
-  bus.emit('reporterEvent', event);
+  if (
+    event.bundleGraph &&
+    event.type === 'buildProgress' &&
+    (event.phase === 'optimizing' || event.phase === 'packaging')
+  ) {
+    bus.emit('reporterEvent', {
+      ...event,
+      bundle: bundleToInternalBundle(event.bundle),
+      bundleGraphRef: event.bundleGraph,
+    });
+  } else {
+    bus.emit('reporterEvent', event);
+  }
 }
diff --git a/packages/core/core/src/worker.js b/packages/core/core/src/worker.js
index 22da7b05041..4664a2e66a9 100644
--- a/packages/core/core/src/worker.js
+++ b/packages/core/core/src/worker.js
@@ -17,7 +17,7 @@ import Transformation, {
   type TransformationOpts,
   type TransformationResult,
 } from './Transformation';
-import {reportWorker} from './ReporterRunner';
+import {reportWorker, report} from './ReporterRunner';
 import PackagerRunner, {type PackageRequestResult} from './PackagerRunner';
 import Validation, {type ValidationOpts} from './Validation';
 import ParcelConfig from './ParcelConfig';
@@ -140,9 +140,13 @@ export async function runPackage(
   let runner = new PackagerRunner({
     config: parcelConfig,
     options,
-    report: reportWorker.bind(null, workerApi),
+    report:
+      typeof bundleGraphReference === 'number'
+        ? reportWorker.bind(null, workerApi)
+        : report,
     previousDevDeps,
     previousInvalidations,
+    useFarm: typeof bundleGraphReference === 'number' ? true : false,
   });
 
   return runner.run(bundleGraph, bundle, invalidDevDeps);

From 350e01e68b01202ff80afbf609b86ed90cec3fd0 Mon Sep 17 00:00:00 2001
From: thebriando <bdo@atlassian.com>
Date: Tue, 20 Sep 2022 10:55:48 +1000
Subject: [PATCH 04/12] Don't serialize if we can skip all bundle subrequests

---
 .../core/core/src/requests/WriteBundlesRequest.js  | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/packages/core/core/src/requests/WriteBundlesRequest.js b/packages/core/core/src/requests/WriteBundlesRequest.js
index 870fbd3507c..891c02f3f13 100644
--- a/packages/core/core/src/requests/WriteBundlesRequest.js
+++ b/packages/core/core/src/requests/WriteBundlesRequest.js
@@ -76,20 +76,18 @@ async function run({input, api, farm, options}: RunInput) {
       return false;
     }
 
-    // Filter out skippable requests.
-    // if (api.canSkipSubrequest(bundleGraph.getHash(bundle))) {
-    //   // console.log('skipping', bundle.id);
-    //   return false;
-    // }
-
     return true;
   });
 
   let ref;
   let dispose;
 
-  // Create shared reference in WorkerFarm if we need to change multiple bundles.
-  if (bundles.length > 1) {
+  // Create shared reference in WorkerFarm if we need to change multiple bundles and if we
+  // can't skip the subrequests for all the bundles
+  if (
+    bundles.length > 1 &&
+    bundles.some(b => !api.canSkipSubrequest(bundleGraph.getHash(b)))
+  ) {
     ({ref, dispose} = await farm.createSharedReference(
       bundleGraph,
       serialize(bundleGraph),

From ddf8a34facecef8788542b9b96cabf4bc1741fd0 Mon Sep 17 00:00:00 2001
From: thebriando <bdo@atlassian.com>
Date: Wed, 5 Oct 2022 13:08:21 -0700
Subject: [PATCH 05/12] Change condition to not serialize with single bundle
 case

---
 packages/core/core/src/requests/WriteBundlesRequest.js | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/packages/core/core/src/requests/WriteBundlesRequest.js b/packages/core/core/src/requests/WriteBundlesRequest.js
index 891c02f3f13..e9089c89973 100644
--- a/packages/core/core/src/requests/WriteBundlesRequest.js
+++ b/packages/core/core/src/requests/WriteBundlesRequest.js
@@ -86,7 +86,8 @@ async function run({input, api, farm, options}: RunInput) {
   // can't skip the subrequests for all the bundles
   if (
     bundles.length > 1 &&
-    bundles.some(b => !api.canSkipSubrequest(bundleGraph.getHash(b)))
+    bundles.filter(b => !api.canSkipSubrequest(bundleGraph.getHash(b))).length >
+      1
   ) {
     ({ref, dispose} = await farm.createSharedReference(
       bundleGraph,

From 32bef5819d3cb29cd286debc6916f536a1dc5281 Mon Sep 17 00:00:00 2001
From: thebriando <bdo@atlassian.com>
Date: Mon, 17 Oct 2022 22:28:39 -0700
Subject: [PATCH 06/12] Prevent serialization in PackageRequest

---
 packages/core/core/src/requests/PackageRequest.js   |  5 +++--
 .../core/core/src/requests/WriteBundlesRequest.js   |  3 +++
 packages/core/workers/src/WorkerFarm.js             | 13 +++++++++----
 3 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/packages/core/core/src/requests/PackageRequest.js b/packages/core/core/src/requests/PackageRequest.js
index 33c4a967071..3740fb217e4 100644
--- a/packages/core/core/src/requests/PackageRequest.js
+++ b/packages/core/core/src/requests/PackageRequest.js
@@ -20,6 +20,7 @@ type PackageRequestInput = {|
   bundle: Bundle,
   bundleGraphReference?: SharedReference,
   optionsRef: SharedReference,
+  shouldSerialize?: boolean,
 |};
 
 type RunInput = {|
@@ -46,8 +47,8 @@ export function createPackageRequest(
 }
 
 async function run({input, api, farm}: RunInput) {
-  let {bundleGraphReference, optionsRef, bundle} = input;
-  let runPackage = farm.createHandle('runPackage');
+  let {bundleGraphReference, optionsRef, bundle, shouldSerialize} = input;
+  let runPackage = farm.createHandle('runPackage', shouldSerialize);
 
   let start = Date.now();
   let {devDeps, invalidDevDeps} = await getDevDepRequests(api);
diff --git a/packages/core/core/src/requests/WriteBundlesRequest.js b/packages/core/core/src/requests/WriteBundlesRequest.js
index e9089c89973..a299156e0f3 100644
--- a/packages/core/core/src/requests/WriteBundlesRequest.js
+++ b/packages/core/core/src/requests/WriteBundlesRequest.js
@@ -84,11 +84,13 @@ async function run({input, api, farm, options}: RunInput) {
 
   // Create shared reference in WorkerFarm if we need to change multiple bundles and if we
   // can't skip the subrequests for all the bundles
+  let shouldSerialize = false;
   if (
     bundles.length > 1 &&
     bundles.filter(b => !api.canSkipSubrequest(bundleGraph.getHash(b))).length >
       1
   ) {
+    shouldSerialize = true;
     ({ref, dispose} = await farm.createSharedReference(
       bundleGraph,
       serialize(bundleGraph),
@@ -102,6 +104,7 @@ async function run({input, api, farm, options}: RunInput) {
           bundleGraph,
           bundleGraphReference: ref,
           optionsRef,
+          shouldSerialize,
         });
         let info = await api.runRequest(request);
 
diff --git a/packages/core/workers/src/WorkerFarm.js b/packages/core/workers/src/WorkerFarm.js
index 03228f4ea88..6cdb42a8df7 100644
--- a/packages/core/workers/src/WorkerFarm.js
+++ b/packages/core/workers/src/WorkerFarm.js
@@ -175,7 +175,7 @@ export default class WorkerFarm extends EventEmitter {
     );
   }
 
-  createHandle(method: string): HandleFunction {
+  createHandle(method: string, shouldSerialize?: boolean): HandleFunction {
     return async (...args) => {
       // Child process workers are slow to start (~600ms).
       // While we're waiting, just run on the main thread.
@@ -187,9 +187,14 @@ export default class WorkerFarm extends EventEmitter {
           this.warmupWorker(method, args);
         }
 
-        let processedArgs = restoreDeserializedObject(
-          prepareForSerialization([...args, false]),
-        );
+        let processedArgs;
+        if (shouldSerialize) {
+          processedArgs = restoreDeserializedObject(
+            prepareForSerialization([...args, false]),
+          );
+        } else {
+          processedArgs = args;
+        }
 
         if (this.localWorkerInit != null) {
           await this.localWorkerInit;

From d3ec1646667b14ce9bf86bfd22f1e6a3d646253b Mon Sep 17 00:00:00 2001
From: thebriando <bdo@atlassian.com>
Date: Mon, 24 Oct 2022 13:09:14 -0700
Subject: [PATCH 07/12] Don't use remote workers when serialization is skipped

---
 packages/core/workers/src/WorkerFarm.js | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/packages/core/workers/src/WorkerFarm.js b/packages/core/workers/src/WorkerFarm.js
index 6cdb42a8df7..057863ae49a 100644
--- a/packages/core/workers/src/WorkerFarm.js
+++ b/packages/core/workers/src/WorkerFarm.js
@@ -175,12 +175,15 @@ export default class WorkerFarm extends EventEmitter {
     );
   }
 
-  createHandle(method: string, shouldSerialize?: boolean): HandleFunction {
+  createHandle(
+    method: string,
+    shouldSerialize: boolean = true,
+  ): HandleFunction {
     return async (...args) => {
       // Child process workers are slow to start (~600ms).
       // While we're waiting, just run on the main thread.
       // This significantly speeds up startup time.
-      if (this.shouldUseRemoteWorkers()) {
+      if (this.shouldUseRemoteWorkers() && shouldSerialize) {
         return this.addCall(method, [...args, false]);
       } else {
         if (this.options.warmWorkers && this.shouldStartRemoteWorkers()) {

From cf5b3ffdaadb3de90104a6d24261e1aad9c496fd Mon Sep 17 00:00:00 2001
From: thebriando <bdo@atlassian.com>
Date: Mon, 24 Oct 2022 14:52:44 -0700
Subject: [PATCH 08/12] Fix import

---
 packages/core/types/index.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/core/types/index.js b/packages/core/types/index.js
index f1bf04575e8..b7de0060f1d 100644
--- a/packages/core/types/index.js
+++ b/packages/core/types/index.js
@@ -5,7 +5,7 @@ import type SourceMap from '@parcel/source-map';
 import type {FileSystem} from '@parcel/fs';
 import type WorkerFarm from '@parcel/workers';
 import type {PackageManager} from '@parcel/package-manager';
-import type InternalBundleGraph from '../core/src/BundleGraph';
+import type InternalBundleGraph from '@parcel/core';
 import type {
   Diagnostic,
   Diagnostifiable,

From 51f357534538fb1451c47365bb48a102d1d8f81f Mon Sep 17 00:00:00 2001
From: thebriando <bdo@atlassian.com>
Date: Mon, 24 Oct 2022 15:56:18 -0700
Subject: [PATCH 09/12] Revert "Fix import"

This reverts commit cf5b3ffdaadb3de90104a6d24261e1aad9c496fd.
---
 packages/core/types/index.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/packages/core/types/index.js b/packages/core/types/index.js
index b7de0060f1d..f1bf04575e8 100644
--- a/packages/core/types/index.js
+++ b/packages/core/types/index.js
@@ -5,7 +5,7 @@ import type SourceMap from '@parcel/source-map';
 import type {FileSystem} from '@parcel/fs';
 import type WorkerFarm from '@parcel/workers';
 import type {PackageManager} from '@parcel/package-manager';
-import type InternalBundleGraph from '@parcel/core';
+import type InternalBundleGraph from '../core/src/BundleGraph';
 import type {
   Diagnostic,
   Diagnostifiable,

From 8bf905ad35f9c6cc594ffdaae13bf1f7f22ae918 Mon Sep 17 00:00:00 2001
From: thebriando <bdo@atlassian.com>
Date: Wed, 26 Oct 2022 14:50:12 -0700
Subject: [PATCH 10/12] Send BundleGraph through separate ReporterEvent

---
 packages/core/core/src/PackagerRunner.js | 28 ++++++++++++++++++------
 packages/core/core/src/ReporterRunner.js |  8 +++++--
 packages/core/types/index.js             | 17 +++++++++-----
 3 files changed, 39 insertions(+), 14 deletions(-)

diff --git a/packages/core/core/src/PackagerRunner.js b/packages/core/core/src/PackagerRunner.js
index dfaa780eec0..05cc443d848 100644
--- a/packages/core/core/src/PackagerRunner.js
+++ b/packages/core/core/src/PackagerRunner.js
@@ -390,11 +390,23 @@ export default class PackagerRunner {
     bundleConfigs: Map<string, Config>,
   ): Promise<BundleResult> {
     let bundle = NamedBundle.get(internalBundle, bundleGraph, this.options);
+    let publicBundleGraph = new BundleGraph<NamedBundleType>(
+      bundleGraph,
+      NamedBundle.get.bind(NamedBundle),
+      this.options,
+    );
+
+    if (this.useFarm) {
+      this.report({
+        type: 'bundleGraph',
+        bundleGraph: publicBundleGraph,
+      });
+    }
+
     this.report({
       type: 'buildProgress',
       phase: 'packaging',
       bundle,
-      bundleGraph: this.useFarm ? undefined : bundleGraph,
     });
 
     let packager = await this.config.getPackager(bundle.name);
@@ -404,11 +416,7 @@ export default class PackagerRunner {
         config: configs.get(name)?.result,
         bundleConfig: bundleConfigs.get(name)?.result,
         bundle,
-        bundleGraph: new BundleGraph<NamedBundleType>(
-          bundleGraph,
-          NamedBundle.get.bind(NamedBundle),
-          this.options,
-        ),
+        bundleGraph: publicBundleGraph,
         getSourceMapReference: map => {
           return this.getSourceMapReference(bundle, map);
         },
@@ -487,11 +495,17 @@ export default class PackagerRunner {
       return {type: bundle.type, contents, map};
     }
 
+    if (this.useFarm) {
+      this.report({
+        type: 'bundleGraph',
+        bundleGraph,
+      });
+    }
+
     this.report({
       type: 'buildProgress',
       phase: 'optimizing',
       bundle,
-      bundleGraph: this.useFarm ? undefined : internalBundleGraph,
     });
 
     let optimized = {
diff --git a/packages/core/core/src/ReporterRunner.js b/packages/core/core/src/ReporterRunner.js
index 6b358871343..a80f7d0da03 100644
--- a/packages/core/core/src/ReporterRunner.js
+++ b/packages/core/core/src/ReporterRunner.js
@@ -21,6 +21,7 @@ import logger, {
 } from '@parcel/logger';
 import PluginOptions from './public/PluginOptions';
 import BundleGraph from './BundleGraph';
+import {bundleGraphToInternalBundleGraph} from './public/BundleGraph';
 
 type Opts = {|
   config: ParcelConfig,
@@ -34,6 +35,7 @@ export default class ReporterRunner {
   options: ParcelOptions;
   pluginOptions: PluginOptions;
   reporters: Array<LoadedPlugin<Reporter>>;
+  bundleGraph: BundleGraph;
 
   constructor(opts: Opts) {
     this.config = opts.config;
@@ -53,7 +55,9 @@ export default class ReporterRunner {
   }
 
   eventHandler: ReporterEvent => void = (event): void => {
-    if (
+    if (event.type === 'bundleGraph') {
+      this.bundleGraph = bundleGraphToInternalBundleGraph(event.bundleGraph);
+    } else if (
       event.type === 'buildProgress' &&
       (event.phase === 'optimizing' || event.phase === 'packaging') &&
       !(event.bundle instanceof NamedBundle)
@@ -65,7 +69,7 @@ export default class ReporterRunner {
       // Convert any internal bundles back to their public equivalents as reporting
       // is public api
       let bundleGraph =
-        event.bundleGraph ??
+        this.bundleGraph ??
         this.workerFarm.workerApi.getSharedReference(
           // $FlowFixMe
           bundleGraphRef,
diff --git a/packages/core/types/index.js b/packages/core/types/index.js
index 4867144a2bd..09792eae736 100644
--- a/packages/core/types/index.js
+++ b/packages/core/types/index.js
@@ -5,7 +5,6 @@ import type SourceMap from '@parcel/source-map';
 import type {FileSystem} from '@parcel/fs';
 import type WorkerFarm from '@parcel/workers';
 import type {PackageManager} from '@parcel/package-manager';
-import type InternalBundleGraph from '../core/src/BundleGraph';
 import type {
   Diagnostic,
   Diagnostifiable,
@@ -1710,7 +1709,11 @@ export type TextLogEvent = {|
 /**
  * @section reporter
  */
-export type LogEvent = ProgressLogEvent | DiagnosticLogEvent | TextLogEvent;
+export type LogEvent =
+  | ProgressLogEvent
+  | DiagnosticLogEvent
+  | TextLogEvent
+  | BundleGraphEvent;
 
 /**
  * The build just started.
@@ -1765,6 +1768,11 @@ export type BundlingProgressEvent = {|
   +phase: 'bundling',
 |};
 
+export type BundleGraphEvent = {|
+  +type: 'bundleGraph',
+  +bundleGraph: BundleGraph<NamedBundle>,
+|};
+
 /**
  * A new Bundle is being packaged.
  * @section reporter
@@ -1773,7 +1781,6 @@ export type PackagingProgressEvent = {|
   +type: 'buildProgress',
   +phase: 'packaging',
   +bundle: NamedBundle,
-  +bundleGraph?: InternalBundleGraph,
 |};
 
 /**
@@ -1784,7 +1791,6 @@ export type OptimizingProgressEvent = {|
   +type: 'buildProgress',
   +phase: 'optimizing',
   +bundle: NamedBundle,
-  +bundleGraph?: InternalBundleGraph,
 |};
 
 /**
@@ -1843,7 +1849,8 @@ export type ReporterEvent =
   | BuildFailureEvent
   | WatchStartEvent
   | WatchEndEvent
-  | ValidationEvent;
+  | ValidationEvent
+  | BundleGraphEvent;
 
 /**
  * @section reporter

From df73a17bd37333cec1421ddfe71a5640a453c00b Mon Sep 17 00:00:00 2001
From: Devon Govett <devongovett@gmail.com>
Date: Sun, 30 Oct 2022 17:59:07 -0700
Subject: [PATCH 11/12] Only serialize and send shared references to workers
 that need them

---
 packages/core/core/src/PackagerRunner.js      | 30 ++------
 packages/core/core/src/Parcel.js              |  2 +-
 packages/core/core/src/ReporterRunner.js      | 30 ++------
 .../core/src/requests/BundleGraphRequest.js   |  7 +-
 .../core/core/src/requests/PackageRequest.js  | 11 ++-
 .../core/src/requests/WriteBundlesRequest.js  | 32 +++------
 packages/core/core/src/types.js               |  1 +
 packages/core/core/src/worker.js              | 14 ++--
 packages/core/types/index.js                  | 14 +---
 packages/core/workers/src/Worker.js           |  3 +-
 packages/core/workers/src/WorkerFarm.js       | 69 +++++++++++++------
 11 files changed, 86 insertions(+), 127 deletions(-)

diff --git a/packages/core/core/src/PackagerRunner.js b/packages/core/core/src/PackagerRunner.js
index 05cc443d848..e31746f51f2 100644
--- a/packages/core/core/src/PackagerRunner.js
+++ b/packages/core/core/src/PackagerRunner.js
@@ -68,7 +68,6 @@ type Opts = {|
   report: ReportFn,
   previousDevDeps: Map<string, string>,
   previousInvalidations: Array<RequestInvalidation>,
-  useFarm: boolean,
 |};
 
 export type PackageRequestResult = {|
@@ -111,7 +110,6 @@ export default class PackagerRunner {
   devDepRequests: Map<string, DevDepRequest>;
   invalidations: Map<string, RequestInvalidation>;
   previousInvalidations: Array<RequestInvalidation>;
-  useFarm: boolean;
 
   constructor({
     config,
@@ -119,7 +117,6 @@ export default class PackagerRunner {
     report,
     previousDevDeps,
     previousInvalidations,
-    useFarm,
   }: Opts) {
     this.config = config;
     this.options = options;
@@ -127,7 +124,6 @@ export default class PackagerRunner {
     this.previousDevDeps = previousDevDeps;
     this.devDepRequests = new Map();
     this.previousInvalidations = previousInvalidations;
-    this.useFarm = useFarm;
     this.invalidations = new Map();
     this.pluginOptions = new PluginOptions(
       optionsProxy(this.options, option => {
@@ -390,19 +386,6 @@ export default class PackagerRunner {
     bundleConfigs: Map<string, Config>,
   ): Promise<BundleResult> {
     let bundle = NamedBundle.get(internalBundle, bundleGraph, this.options);
-    let publicBundleGraph = new BundleGraph<NamedBundleType>(
-      bundleGraph,
-      NamedBundle.get.bind(NamedBundle),
-      this.options,
-    );
-
-    if (this.useFarm) {
-      this.report({
-        type: 'bundleGraph',
-        bundleGraph: publicBundleGraph,
-      });
-    }
-
     this.report({
       type: 'buildProgress',
       phase: 'packaging',
@@ -416,7 +399,11 @@ export default class PackagerRunner {
         config: configs.get(name)?.result,
         bundleConfig: bundleConfigs.get(name)?.result,
         bundle,
-        bundleGraph: publicBundleGraph,
+        bundleGraph: new BundleGraph<NamedBundleType>(
+          bundleGraph,
+          NamedBundle.get.bind(NamedBundle),
+          this.options,
+        ),
         getSourceMapReference: map => {
           return this.getSourceMapReference(bundle, map);
         },
@@ -495,13 +482,6 @@ export default class PackagerRunner {
       return {type: bundle.type, contents, map};
     }
 
-    if (this.useFarm) {
-      this.report({
-        type: 'bundleGraph',
-        bundleGraph,
-      });
-    }
-
     this.report({
       type: 'buildProgress',
       phase: 'optimizing',
diff --git a/packages/core/core/src/Parcel.js b/packages/core/core/src/Parcel.js
index 8688c081716..40e9c448b8b 100644
--- a/packages/core/core/src/Parcel.js
+++ b/packages/core/core/src/Parcel.js
@@ -110,7 +110,7 @@ export default class Parcel {
     await resolvedOptions.cache.ensure();
 
     let {dispose: disposeOptions, ref: optionsRef} =
-      await this.#farm.createSharedReference(resolvedOptions);
+      await this.#farm.createSharedReference(resolvedOptions, false);
     this.#optionsRef = optionsRef;
 
     this.#disposable = new Disposable();
diff --git a/packages/core/core/src/ReporterRunner.js b/packages/core/core/src/ReporterRunner.js
index a80f7d0da03..9b07912bb7e 100644
--- a/packages/core/core/src/ReporterRunner.js
+++ b/packages/core/core/src/ReporterRunner.js
@@ -21,7 +21,6 @@ import logger, {
 } from '@parcel/logger';
 import PluginOptions from './public/PluginOptions';
 import BundleGraph from './BundleGraph';
-import {bundleGraphToInternalBundleGraph} from './public/BundleGraph';
 
 type Opts = {|
   config: ParcelConfig,
@@ -35,7 +34,6 @@ export default class ReporterRunner {
   options: ParcelOptions;
   pluginOptions: PluginOptions;
   reporters: Array<LoadedPlugin<Reporter>>;
-  bundleGraph: BundleGraph;
 
   constructor(opts: Opts) {
     this.config = opts.config;
@@ -55,9 +53,7 @@ export default class ReporterRunner {
   }
 
   eventHandler: ReporterEvent => void = (event): void => {
-    if (event.type === 'bundleGraph') {
-      this.bundleGraph = bundleGraphToInternalBundleGraph(event.bundleGraph);
-    } else if (
+    if (
       event.type === 'buildProgress' &&
       (event.phase === 'optimizing' || event.phase === 'packaging') &&
       !(event.bundle instanceof NamedBundle)
@@ -68,12 +64,10 @@ export default class ReporterRunner {
       let bundle: InternalBundle = event.bundle;
       // Convert any internal bundles back to their public equivalents as reporting
       // is public api
-      let bundleGraph =
-        this.bundleGraph ??
-        this.workerFarm.workerApi.getSharedReference(
-          // $FlowFixMe
-          bundleGraphRef,
-        );
+      let bundleGraph = this.workerFarm.workerApi.getSharedReference(
+        // $FlowFixMe
+        bundleGraphRef,
+      );
       invariant(bundleGraph instanceof BundleGraph);
       // $FlowFixMe[incompatible-call]
       this.report({
@@ -137,17 +131,5 @@ export function reportWorker(workerApi: WorkerApi, event: ReporterEvent) {
 }
 
 export function report(event: ReporterEvent) {
-  if (
-    event.bundleGraph &&
-    event.type === 'buildProgress' &&
-    (event.phase === 'optimizing' || event.phase === 'packaging')
-  ) {
-    bus.emit('reporterEvent', {
-      ...event,
-      bundle: bundleToInternalBundle(event.bundle),
-      bundleGraphRef: event.bundleGraph,
-    });
-  } else {
-    bus.emit('reporterEvent', event);
-  }
+  bus.emit('reporterEvent', event);
 }
diff --git a/packages/core/core/src/requests/BundleGraphRequest.js b/packages/core/core/src/requests/BundleGraphRequest.js
index 248628450f5..44e2ac1e33a 100644
--- a/packages/core/core/src/requests/BundleGraphRequest.js
+++ b/packages/core/core/src/requests/BundleGraphRequest.js
@@ -48,7 +48,7 @@ import {
   getConfigHash,
   type PluginWithLoadConfig,
 } from './ConfigRequest';
-import {cacheSerializedObject, deserializeToCache} from '../serializer';
+import {deserializeToCache} from '../serializer';
 import {
   joinProjectPath,
   fromProjectPathRelative,
@@ -356,11 +356,8 @@ class BundlerRunner {
       bundleGraphEdgeTypes,
     );
 
-    // Store the serialized bundle graph in an in memory cache so that we avoid serializing it
-    // many times to send to each worker, and in build mode, when writing to cache on shutdown.
-    // Also, pre-compute the hashes for each bundle so they are only computed once and shared between workers.
+    // Pre-compute the hashes for each bundle so they are only computed once and shared between workers.
     internalBundleGraph.getBundleGraphHash();
-    cacheSerializedObject(internalBundleGraph);
 
     // Recompute the cache key to account for new dev dependencies and invalidations.
     let {cacheKey: updatedCacheKey} = await this.getHashes(graph);
diff --git a/packages/core/core/src/requests/PackageRequest.js b/packages/core/core/src/requests/PackageRequest.js
index 4d540112c7c..d2d3067d06a 100644
--- a/packages/core/core/src/requests/PackageRequest.js
+++ b/packages/core/core/src/requests/PackageRequest.js
@@ -18,9 +18,9 @@ import createParcelConfigRequest from './ParcelConfigRequest';
 type PackageRequestInput = {|
   bundleGraph: BundleGraph,
   bundle: Bundle,
-  bundleGraphReference?: SharedReference,
+  bundleGraphReference: SharedReference,
   optionsRef: SharedReference,
-  shouldSerialize?: boolean,
+  useMainThread?: boolean,
 |};
 
 type RunInput = {|
@@ -47,8 +47,8 @@ export function createPackageRequest(
 }
 
 async function run({input, api, farm}: RunInput) {
-  let {bundleGraphReference, optionsRef, bundle, shouldSerialize} = input;
-  let runPackage = farm.createHandle('runPackage', shouldSerialize);
+  let {bundleGraphReference, optionsRef, bundle, useMainThread} = input;
+  let runPackage = farm.createHandle('runPackage', useMainThread);
 
   let start = Date.now();
   let {devDeps, invalidDevDeps} = await getDevDepRequests(api);
@@ -59,8 +59,7 @@ async function run({input, api, farm}: RunInput) {
   let {devDepRequests, configRequests, bundleInfo, invalidations} =
     (await runPackage({
       bundle,
-      bundleGraphReference:
-        bundleGraphReference == null ? input.bundleGraph : bundleGraphReference,
+      bundleGraphReference,
       optionsRef,
       configCachePath: cachePath,
       previousDevDeps: devDeps,
diff --git a/packages/core/core/src/requests/WriteBundlesRequest.js b/packages/core/core/src/requests/WriteBundlesRequest.js
index f3f4bca9f46..f527c0cb41e 100644
--- a/packages/core/core/src/requests/WriteBundlesRequest.js
+++ b/packages/core/core/src/requests/WriteBundlesRequest.js
@@ -9,7 +9,6 @@ import type BundleGraph from '../BundleGraph';
 import type {BundleInfo} from '../PackagerRunner';
 
 import {HASH_REF_PREFIX} from '../constants';
-import {serialize} from '../serializer';
 import {joinProjectPath} from '../projectPath';
 import nullthrows from 'nullthrows';
 import {hashString} from '@parcel/hash';
@@ -49,6 +48,7 @@ export default function createWriteBundlesRequest(
 
 async function run({input, api, farm, options}: RunInput) {
   let {bundleGraph, optionsRef} = input;
+  let {ref, dispose} = await farm.createSharedReference(bundleGraph);
 
   api.invalidateOnOptionChange('shouldContentHash');
 
@@ -79,23 +79,13 @@ async function run({input, api, farm, options}: RunInput) {
     return true;
   });
 
-  let ref;
-  let dispose;
-
-  // Create shared reference in WorkerFarm if we need to change multiple bundles and if we
-  // can't skip the subrequests for all the bundles
-  let shouldSerialize = false;
-  if (
-    bundles.length > 1 &&
-    bundles.filter(b => !api.canSkipSubrequest(bundleGraph.getHash(b))).length >
-      1
-  ) {
-    shouldSerialize = true;
-    ({ref, dispose} = await farm.createSharedReference(
-      bundleGraph,
-      serialize(bundleGraph),
-    ));
-  }
+  // Package on the main thread if there is only one bundle to package.
+  // This avoids the cost of serializing the bundle graph for single file change builds.
+  let useMainThread =
+    bundles.length === 1 ||
+    bundles.filter(b => !api.canSkipSubrequest(bundleGraph.getHash(b)))
+      .length === 1;
+
   try {
     await Promise.all(
       bundles.map(async bundle => {
@@ -104,7 +94,7 @@ async function run({input, api, farm, options}: RunInput) {
           bundleGraph,
           bundleGraphReference: ref,
           optionsRef,
-          shouldSerialize,
+          useMainThread,
         });
 
         let info = await api.runRequest(request);
@@ -148,9 +138,7 @@ async function run({input, api, farm, options}: RunInput) {
     api.storeResult(res);
     return res;
   } finally {
-    if (dispose) {
-      await dispose();
-    }
+    await dispose();
   }
 }
 
diff --git a/packages/core/core/src/types.js b/packages/core/core/src/types.js
index f355f636691..474ae5ba9cf 100644
--- a/packages/core/core/src/types.js
+++ b/packages/core/core/src/types.js
@@ -342,6 +342,7 @@ export type AssetRequestInput = {|
   optionsRef: SharedReference,
   isURL?: boolean,
   query?: ?string,
+  isSingleChangeRebuild?: boolean,
 |};
 
 export type AssetRequestResult = Array<Asset>;
diff --git a/packages/core/core/src/worker.js b/packages/core/core/src/worker.js
index 4664a2e66a9..b093ce2e3b5 100644
--- a/packages/core/core/src/worker.js
+++ b/packages/core/core/src/worker.js
@@ -25,6 +25,7 @@ import {registerCoreWithSerializer} from './utils';
 import {clearBuildCaches} from './buildCache';
 import {init as initSourcemaps} from '@parcel/source-map';
 import {init as initHash} from '@parcel/hash';
+import WorkerFarm from '@parcel/workers';
 
 import '@parcel/cache'; // register with serializer
 import '@parcel/package-manager';
@@ -121,7 +122,7 @@ export async function runPackage(
     previousInvalidations,
   }: {|
     bundle: Bundle,
-    bundleGraphReference: SharedReference | BundleGraph,
+    bundleGraphReference: SharedReference,
     configCachePath: string,
     optionsRef: SharedReference,
     previousDevDeps: Map<string, string>,
@@ -129,10 +130,7 @@ export async function runPackage(
     previousInvalidations: Array<RequestInvalidation>,
   |},
 ): Promise<PackageRequestResult> {
-  let bundleGraph =
-    typeof bundleGraphReference === 'number'
-      ? workerApi.getSharedReference(bundleGraphReference)
-      : bundleGraphReference;
+  let bundleGraph = workerApi.getSharedReference(bundleGraphReference);
   invariant(bundleGraph instanceof BundleGraph);
   let options = loadOptions(optionsRef, workerApi);
   let parcelConfig = await loadConfig(configCachePath, options);
@@ -140,13 +138,9 @@ export async function runPackage(
   let runner = new PackagerRunner({
     config: parcelConfig,
     options,
-    report:
-      typeof bundleGraphReference === 'number'
-        ? reportWorker.bind(null, workerApi)
-        : report,
+    report: WorkerFarm.isWorker() ? reportWorker.bind(null, workerApi) : report,
     previousDevDeps,
     previousInvalidations,
-    useFarm: typeof bundleGraphReference === 'number' ? true : false,
   });
 
   return runner.run(bundleGraph, bundle, invalidDevDeps);
diff --git a/packages/core/types/index.js b/packages/core/types/index.js
index 0185efa8149..b33e362d816 100644
--- a/packages/core/types/index.js
+++ b/packages/core/types/index.js
@@ -1710,11 +1710,7 @@ export type TextLogEvent = {|
 /**
  * @section reporter
  */
-export type LogEvent =
-  | ProgressLogEvent
-  | DiagnosticLogEvent
-  | TextLogEvent
-  | BundleGraphEvent;
+export type LogEvent = ProgressLogEvent | DiagnosticLogEvent | TextLogEvent;
 
 /**
  * The build just started.
@@ -1769,11 +1765,6 @@ export type BundlingProgressEvent = {|
   +phase: 'bundling',
 |};
 
-export type BundleGraphEvent = {|
-  +type: 'bundleGraph',
-  +bundleGraph: BundleGraph<NamedBundle>,
-|};
-
 /**
  * A new Bundle is being packaged.
  * @section reporter
@@ -1850,8 +1841,7 @@ export type ReporterEvent =
   | BuildFailureEvent
   | WatchStartEvent
   | WatchEndEvent
-  | ValidationEvent
-  | BundleGraphEvent;
+  | ValidationEvent;
 
 /**
  * @section reporter
diff --git a/packages/core/workers/src/Worker.js b/packages/core/workers/src/Worker.js
index 833251983ad..e3ad9d1c13c 100644
--- a/packages/core/workers/src/Worker.js
+++ b/packages/core/workers/src/Worker.js
@@ -31,7 +31,7 @@ export default class Worker extends EventEmitter {
   +options: WorkerOpts;
   worker: WorkerImpl;
   id: number = WORKER_ID++;
-  sharedReferences: $ReadOnlyMap<SharedReference, mixed> = new Map();
+  sentSharedReferences: Set<SharedReference> = new Set();
 
   calls: Map<number, WorkerCall> = new Map();
   exitCode: ?number = null;
@@ -135,6 +135,7 @@ export default class Worker extends EventEmitter {
   }
 
   sendSharedReference(ref: SharedReference, value: mixed): Promise<any> {
+    this.sentSharedReferences.add(ref);
     return new Promise((resolve, reject) => {
       this.call({
         method: 'createSharedReference',
diff --git a/packages/core/workers/src/WorkerFarm.js b/packages/core/workers/src/WorkerFarm.js
index 057863ae49a..afeb0717e61 100644
--- a/packages/core/workers/src/WorkerFarm.js
+++ b/packages/core/workers/src/WorkerFarm.js
@@ -76,6 +76,7 @@ export default class WorkerFarm extends EventEmitter {
   handles: Map<number, Handle> = new Map();
   sharedReferences: Map<SharedReference, mixed> = new Map();
   sharedReferencesByValue: Map<mixed, SharedReference> = new Map();
+  serializedSharedReferences: Map<SharedReference, ?ArrayBuffer> = new Map();
   profiler: ?Profiler;
 
   constructor(farmOptions: $Shape<FarmOptions> = {}) {
@@ -175,15 +176,12 @@ export default class WorkerFarm extends EventEmitter {
     );
   }
 
-  createHandle(
-    method: string,
-    shouldSerialize: boolean = true,
-  ): HandleFunction {
+  createHandle(method: string, useMainThread: boolean = false): HandleFunction {
     return async (...args) => {
       // Child process workers are slow to start (~600ms).
       // While we're waiting, just run on the main thread.
       // This significantly speeds up startup time.
-      if (this.shouldUseRemoteWorkers() && shouldSerialize) {
+      if (this.shouldUseRemoteWorkers() && !useMainThread) {
         return this.addCall(method, [...args, false]);
       } else {
         if (this.options.warmWorkers && this.shouldStartRemoteWorkers()) {
@@ -191,7 +189,7 @@ export default class WorkerFarm extends EventEmitter {
         }
 
         let processedArgs;
-        if (shouldSerialize) {
+        if (!useMainThread) {
           processedArgs = restoreDeserializedObject(
             prepareForSerialization([...args, false]),
           );
@@ -281,11 +279,24 @@ export default class WorkerFarm extends EventEmitter {
       }
 
       if (worker.calls.size < this.options.maxConcurrentCallsPerWorker) {
-        worker.call(this.callQueue.shift());
+        this.callWorker(worker, this.callQueue.shift());
       }
     }
   }
 
+  async callWorker(worker: Worker, call: WorkerCall): Promise<void> {
+    for (let ref of this.sharedReferences.keys()) {
+      if (!worker.sentSharedReferences.has(ref)) {
+        await worker.sendSharedReference(
+          ref,
+          this.getSerializedSharedReference(ref),
+        );
+      }
+    }
+
+    worker.call(call);
+  }
+
   async processRequest(
     data: {|
       location: FilePath,
@@ -408,33 +419,31 @@ export default class WorkerFarm extends EventEmitter {
     return handle;
   }
 
-  async createSharedReference(
+  createSharedReference(
     value: mixed,
-    // An optional, pre-serialized representation of the value to be used
-    // in its place.
-    buffer?: Buffer,
-  ): Promise<{|ref: SharedReference, dispose(): Promise<mixed>|}> {
+    isCacheable: boolean = true,
+  ): {|ref: SharedReference, dispose(): Promise<mixed>|} {
     let ref = referenceId++;
     this.sharedReferences.set(ref, value);
     this.sharedReferencesByValue.set(value, ref);
-
-    let toSend = buffer ? buffer.buffer : value;
-    let promises = [];
-    for (let worker of this.workers.values()) {
-      if (worker.ready) {
-        promises.push(worker.sendSharedReference(ref, toSend));
-      }
+    if (!isCacheable) {
+      this.serializedSharedReferences.set(ref, null);
     }
 
-    await Promise.all(promises);
-
     return {
       ref,
       dispose: () => {
         this.sharedReferences.delete(ref);
         this.sharedReferencesByValue.delete(value);
+        this.serializedSharedReferences.delete(ref);
+
         let promises = [];
         for (let worker of this.workers.values()) {
+          if (!worker.sentSharedReferences.has(ref)) {
+            continue;
+          }
+
+          worker.sentSharedReferences.delete(ref);
           promises.push(
             new Promise((resolve, reject) => {
               worker.call({
@@ -453,6 +462,24 @@ export default class WorkerFarm extends EventEmitter {
     };
   }
 
+  getSerializedSharedReference(ref: SharedReference): ArrayBuffer {
+    let cached = this.serializedSharedReferences.get(ref);
+    if (cached) {
+      return cached;
+    }
+
+    let value = this.sharedReferences.get(ref);
+    let buf = serialize(value).buffer;
+
+    // If the reference was created with the isCacheable option set to false,
+    // serializedSharedReferences will contain `null` as the value.
+    if (cached !== null) {
+      this.serializedSharedReferences.set(ref, buf);
+    }
+
+    return buf;
+  }
+
   async startProfile() {
     let promises = [];
     for (let worker of this.workers.values()) {

From 48c8e7972bd589a08af1716744780a0cc5b8f3b3 Mon Sep 17 00:00:00 2001
From: Devon Govett <devongovett@gmail.com>
Date: Sun, 30 Oct 2022 18:01:14 -0700
Subject: [PATCH 12/12] Also transform on the main thread if only one file
 changed

---
 packages/core/core/src/RequestTracker.js      | 21 +++++++++++++++++++
 .../core/src/requests/AssetGraphRequest.js    |  7 +++++++
 .../core/core/src/requests/AssetRequest.js    |  5 ++++-
 packages/core/core/test/TargetRequest.test.js |  3 +++
 4 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/packages/core/core/src/RequestTracker.js b/packages/core/core/src/RequestTracker.js
index 08e5c73b453..4be5114b359 100644
--- a/packages/core/core/src/RequestTracker.js
+++ b/packages/core/core/src/RequestTracker.js
@@ -145,6 +145,7 @@ export type RunAPI = {|
   getRequestResult<T>(contentKey: ContentKey): Async<?T>,
   getPreviousResult<T>(ifMatch?: string): Async<?T>,
   getSubRequests(): Array<StoredRequest>,
+  getInvalidSubRequests(): Array<StoredRequest>,
   canSkipSubrequest(ContentKey): boolean,
   runRequest: <TInput, TResult>(
     subRequest: Request<TInput, TResult>,
@@ -635,6 +636,25 @@ export class RequestGraph extends ContentGraph<
     });
   }
 
+  getInvalidSubRequests(requestNodeId: NodeId): Array<StoredRequest> {
+    if (!this.hasNode(requestNodeId)) {
+      return [];
+    }
+
+    let subRequests = this.getNodeIdsConnectedFrom(
+      requestNodeId,
+      requestGraphEdgeTypes.subrequest,
+    );
+
+    return subRequests
+      .filter(id => this.invalidNodeIds.has(id))
+      .map(nodeId => {
+        let node = nullthrows(this.getNode(nodeId));
+        invariant(node.type === 'request');
+        return node.value;
+      });
+  }
+
   invalidateFileNameNode(
     node: FileNameNode,
     filePath: ProjectPath,
@@ -1028,6 +1048,7 @@ export default class RequestTracker {
         this.storeResult(requestId, result, cacheKey);
       },
       getSubRequests: () => this.graph.getSubRequests(requestId),
+      getInvalidSubRequests: () => this.graph.getInvalidSubRequests(requestId),
       getPreviousResult: <T>(ifMatch?: string): Async<?T> => {
         let contentKey = nullthrows(this.graph.getNode(requestId)?.id);
         return this.getRequestResult<T>(contentKey, ifMatch);
diff --git a/packages/core/core/src/requests/AssetGraphRequest.js b/packages/core/core/src/requests/AssetGraphRequest.js
index 2b0d55073d5..7275a016355 100644
--- a/packages/core/core/src/requests/AssetGraphRequest.js
+++ b/packages/core/core/src/requests/AssetGraphRequest.js
@@ -121,6 +121,7 @@ export class AssetGraphBuilder {
   cacheKey: string;
   shouldBuildLazily: boolean;
   requestedAssetIds: Set<string>;
+  isSingleChangeRebuild: boolean;
 
   constructor(
     {input, api, options}: RunInput,
@@ -151,6 +152,9 @@ export class AssetGraphBuilder {
       `${PARCEL_VERSION}${name}${JSON.stringify(entries) ?? ''}${options.mode}`,
     );
 
+    this.isSingleChangeRebuild =
+      api.getInvalidSubRequests().filter(req => req.type === 'asset_request')
+        .length === 1;
     this.queue = new PromiseQueue();
   }
 
@@ -989,6 +993,7 @@ export class AssetGraphBuilder {
       ...input,
       name: this.name,
       optionsRef: this.optionsRef,
+      isSingleChangeRebuild: this.isSingleChangeRebuild,
     });
     let assets = await this.api.runRequest<AssetRequestInput, Array<Asset>>(
       request,
@@ -1015,6 +1020,8 @@ export class AssetGraphBuilder {
     } else {
       this.assetGraph.safeToIncrementallyBundle = false;
     }
+
+    this.isSingleChangeRebuild = false;
   }
 
   /**
diff --git a/packages/core/core/src/requests/AssetRequest.js b/packages/core/core/src/requests/AssetRequest.js
index a02541d092e..520ede77cde 100644
--- a/packages/core/core/src/requests/AssetRequest.js
+++ b/packages/core/core/src/requests/AssetRequest.js
@@ -133,7 +133,10 @@ async function run({input, api, farm, invalidateReason, options}: RunInput) {
     invalidations,
     invalidateOnFileCreate,
     devDepRequests,
-  } = (await farm.createHandle('runTransform')({
+  } = (await farm.createHandle(
+    'runTransform',
+    input.isSingleChangeRebuild,
+  )({
     configCachePath: cachePath,
     optionsRef,
     request,
diff --git a/packages/core/core/test/TargetRequest.test.js b/packages/core/core/test/TargetRequest.test.js
index b8db4e11e69..646574da410 100644
--- a/packages/core/core/test/TargetRequest.test.js
+++ b/packages/core/core/test/TargetRequest.test.js
@@ -93,6 +93,9 @@ describe('TargetResolver', () => {
     getSubRequests() {
       return [];
     },
+    getInvalidSubRequests() {
+      return [];
+    },
   };
 
   it('resolves exactly specified targets', async () => {