From e51955f9d4fa4009a611ba7e88bd85d0fd4c53a2 Mon Sep 17 00:00:00 2001
From: Shinobu Hayashi <PhilisPaxil@gmail.com>
Date: Mon, 9 May 2022 11:43:49 +0900
Subject: [PATCH] Feature(transformer): re-implement postProcess API (#8026)

---
 packages/core/core/src/Transformation.js | 67 +++++++++++++++++++++++-
 packages/core/types/index.js             | 21 +++++---
 2 files changed, 79 insertions(+), 9 deletions(-)

diff --git a/packages/core/core/src/Transformation.js b/packages/core/core/src/Transformation.js
index d8e90198d8f..4880b509e65 100644
--- a/packages/core/core/src/Transformation.js
+++ b/packages/core/core/src/Transformation.js
@@ -74,9 +74,14 @@ import {
   toProjectPath,
 } from './projectPath';
 import {invalidateOnFileCreateToInternal} from './utils';
+import invariant from 'assert';
 
 type GenerateFunc = (input: UncommittedAsset) => Promise<GenerateOutput>;
 
+type PostProcessFunc = (
+  Array<UncommittedAsset>,
+) => Promise<Array<UncommittedAsset> | null>;
+
 export type TransformationOpts = {|
   options: ParcelOptions,
   config: ParcelConfig,
@@ -336,7 +341,34 @@ export default class Transformation {
       }
     }
 
-    return finalAssets;
+    if (!pipeline.postProcess) {
+      return finalAssets;
+    }
+
+    let pipelineHash = await this.getPipelineHash(pipeline);
+    let invalidationHash = await getInvalidationHash(
+      finalAssets.flatMap(asset => asset.getInvalidations()),
+      this.options,
+    );
+    let processedCacheEntry = await this.readFromCache(
+      this.getCacheKey(finalAssets, invalidationHash, pipelineHash),
+    );
+
+    invariant(pipeline.postProcess != null);
+    let processedFinalAssets: Array<UncommittedAsset> =
+      processedCacheEntry ?? (await pipeline.postProcess(finalAssets)) ?? [];
+
+    if (!processedCacheEntry) {
+      await this.writeToCache(
+        this.getCacheKey(processedFinalAssets, invalidationHash, pipelineHash),
+        processedFinalAssets,
+
+        invalidationHash,
+        pipelineHash,
+      );
+    }
+
+    return processedFinalAssets;
   }
 
   async getPipelineHash(pipeline: Pipeline): Promise<string> {
@@ -426,6 +458,8 @@ export default class Transformation {
             transformer.plugin,
             transformer.name,
             transformer.config,
+            transformer.configKeyPath,
+            this.parcelConfig,
           );
 
           for (let result of transformerResults) {
@@ -695,6 +729,8 @@ export default class Transformation {
     transformer: Transformer<mixed>,
     transformerName: string,
     preloadedConfig: ?Config,
+    configKeyPath?: string,
+    parcelConfig: ParcelConfig,
   ): Promise<$ReadOnlyArray<TransformerResult | UncommittedAsset>> {
     const logger = new PluginLogger({origin: transformerName});
 
@@ -786,7 +822,7 @@ export default class Transformation {
       });
     let results = await normalizeAssets(this.options, transfomerResult);
 
-    // Create generate function that can be called later
+    // Create generate and postProcess function that can be called later
     asset.generate = (): Promise<GenerateOutput> => {
       let publicAsset = new Asset(asset);
       if (transformer.generate && asset.ast) {
@@ -805,6 +841,32 @@ export default class Transformation {
       );
     };
 
+    let postProcess = transformer.postProcess;
+    if (postProcess) {
+      pipeline.postProcess = async (
+        assets: Array<UncommittedAsset>,
+      ): Promise<Array<UncommittedAsset> | null> => {
+        let results = await postProcess.call(transformer, {
+          assets: assets.map(asset => new MutableAsset(asset)),
+          config,
+          options: pipeline.pluginOptions,
+          resolve,
+          logger,
+        });
+
+        return Promise.all(
+          results.map(result =>
+            asset.createChildAsset(
+              result,
+              transformerName,
+              parcelConfig.filePath,
+              // configKeyPath,
+            ),
+          ),
+        );
+      };
+    }
+
     return results;
   }
 }
@@ -816,6 +878,7 @@ type Pipeline = {|
   pluginOptions: PluginOptions,
   resolverRunner: ResolverRunner,
   workerApi: WorkerApi,
+  postProcess?: PostProcessFunc,
   generate?: GenerateFunc,
 |};
 
diff --git a/packages/core/types/index.js b/packages/core/types/index.js
index d4def0daf83..57c29b0c5ee 100644
--- a/packages/core/types/index.js
+++ b/packages/core/types/index.js
@@ -186,7 +186,7 @@ export type EnvironmentOptions = {|
  */
 export type VersionMap = {
   [string]: string,
-  ...,
+  ...
 };
 
 export type EnvironmentFeature =
@@ -398,9 +398,7 @@ export interface AssetSymbols // eslint-disable-next-line no-undef
    * This is the default state.
    */
   +isCleared: boolean;
-  get(
-    exportSymbol: Symbol,
-  ): ?{|
+  get(exportSymbol: Symbol): ?{|
     local: Symbol,
     loc: ?SourceLocation,
     meta?: ?Meta,
@@ -443,9 +441,7 @@ export interface MutableDependencySymbols // eslint-disable-next-line no-undef
    * This is the default state.
    */
   +isCleared: boolean;
-  get(
-    exportSymbol: Symbol,
-  ): ?{|
+  get(exportSymbol: Symbol): ?{|
     local: Symbol,
     loc: ?SourceLocation,
     isWeak: boolean,
@@ -1045,6 +1041,17 @@ export type Transformer<ConfigType> = {|
     options: PluginOptions,
     logger: PluginLogger,
   |}): Async<Array<TransformerResult | MutableAsset>>,
+  /**
+   * Do some processing after the transformation
+   * @experimental
+   */
+  postProcess?: ({|
+    assets: Array<MutableAsset>,
+    config: ConfigType,
+    resolve: ResolveFn,
+    options: PluginOptions,
+    logger: PluginLogger,
+  |}) => Async<Array<TransformerResult>>,
   /** Stringify the AST */
   generate?: ({|
     asset: Asset,