From 86754e4750bedcad1e51a607e09804d0183b074f Mon Sep 17 00:00:00 2001
From: Charles Lyding <19598772+clydin@users.noreply.github.com>
Date: Tue, 20 Apr 2021 21:21:29 -0400
Subject: [PATCH] refactor(@ngtools/webpack): use Webpack 5 modified/removed
 file sets for changed list

Webpack 5 directly provides the set of modified and removed files. This feature allows for the removal of the file timestamp logic within the plugin that was previously used to generated the set of changed files on a rebuild.
---
 packages/ngtools/webpack/src/ivy/cache.ts  | 34 ++++------------------
 packages/ngtools/webpack/src/ivy/plugin.ts | 15 +++++-----
 2 files changed, 13 insertions(+), 36 deletions(-)

diff --git a/packages/ngtools/webpack/src/ivy/cache.ts b/packages/ngtools/webpack/src/ivy/cache.ts
index 1b3856b238..b6363a0351 100644
--- a/packages/ngtools/webpack/src/ivy/cache.ts
+++ b/packages/ngtools/webpack/src/ivy/cache.ts
@@ -11,36 +11,12 @@ import { normalizePath } from './paths';
 export class SourceFileCache extends Map<string, ts.SourceFile> {
   private readonly angularDiagnostics = new Map<ts.SourceFile, ts.Diagnostic[]>();
 
-  invalidate(
-    fileTimestamps: Map<string, 'ignore' | number | { safeTime: number } | null>,
-    buildTimestamp: number,
-  ): Set<string> {
-    const changedFiles = new Set<string>();
-    for (const [file, timeOrEntry] of fileTimestamps) {
-      if (timeOrEntry === 'ignore') {
-        continue;
-      }
-
-      let time;
-      if (typeof timeOrEntry === 'number') {
-        time = timeOrEntry;
-      } else if (timeOrEntry) {
-        time = timeOrEntry.safeTime;
-      }
-
-      if (!time || time >= buildTimestamp) {
-        // Cache stores paths using the POSIX directory separator
-        const normalizedFile = normalizePath(file);
-        const sourceFile = this.get(normalizedFile);
-        if (sourceFile) {
-          this.delete(normalizedFile);
-          this.angularDiagnostics.delete(sourceFile);
-        }
-        changedFiles.add(normalizedFile);
-      }
+  invalidate(file: string): void {
+    const sourceFile = this.get(file);
+    if (sourceFile) {
+      this.delete(file);
+      this.angularDiagnostics.delete(sourceFile);
     }
-
-    return changedFiles;
   }
 
   updateAngularDiagnostics(sourceFile: ts.SourceFile, diagnostics: ts.Diagnostic[]): void {
diff --git a/packages/ngtools/webpack/src/ivy/plugin.ts b/packages/ngtools/webpack/src/ivy/plugin.ts
index b35ea5edda..970d826b2e 100644
--- a/packages/ngtools/webpack/src/ivy/plugin.ts
+++ b/packages/ngtools/webpack/src/ivy/plugin.ts
@@ -95,7 +95,6 @@ export class AngularWebpackPlugin {
   private ngtscNextProgram?: NgtscProgram;
   private builder?: ts.EmitAndSemanticDiagnosticsBuilderProgram;
   private sourceFileCache?: SourceFileCache;
-  private buildTimestamp!: number;
   private readonly fileDependencies = new Map<string, Set<string>>();
   private readonly requiredFilesToEmit = new Set<string>();
   private readonly requiredFilesToEmitCache = new Map<string, EmitFileResult | undefined>();
@@ -204,12 +203,15 @@ export class AngularWebpackPlugin {
       let cache = this.sourceFileCache;
       let changedFiles;
       if (cache) {
-        // Invalidate existing cache based on compiler file timestamps
-        changedFiles = cache.invalidate(compiler.fileTimestamps, this.buildTimestamp);
+        changedFiles = new Set<string>();
+        for (const changedFile of [...compiler.modifiedFiles, ...compiler.removedFiles]) {
+          const normalizedChangedFile = normalizePath(changedFile);
+          // Invalidate file dependencies
+          this.fileDependencies.delete(normalizedChangedFile);
+          // Invalidate existing cache
+          cache.invalidate(normalizedChangedFile);
 
-        // Invalidate file dependencies of changed files
-        for (const changedFile of changedFiles) {
-          this.fileDependencies.delete(normalizePath(changedFile));
+          changedFiles.add(normalizedChangedFile);
         }
       } else {
         // Initialize a new cache
@@ -219,7 +221,6 @@ export class AngularWebpackPlugin {
           this.sourceFileCache = cache;
         }
       }
-      this.buildTimestamp = Date.now();
       augmentHostWithCaching(host, cache);
 
       const moduleResolutionCache = ts.createModuleResolutionCache(