From da49ae0c7267739bf10d00793d8ad59fd9a72237 Mon Sep 17 00:00:00 2001
From: Charles Lyding <19598772+clydin@users.noreply.github.com>
Date: Thu, 22 Feb 2024 10:05:38 -0500
Subject: [PATCH] fix(@angular-devkit/build-angular): improve rebuild
 performance with loaders and prebundling

Processing overhead has been reduce during resolution when the fallback path is enabled
for prebundling due to either prebundling exclusions or custom loader options being present.
The resolution logic now follows the same behavior as the underlying bundler's external
package option and avoids the need for an additional bundler resolution roundtrip. While
the overhead of the plugin itself is still present, the execution cost is now greatly reduced.
Further optimizations to conditionally include the plugin based on code analysis heuristics
may be considered in the future.
---
 .../tools/esbuild/external-packages-plugin.ts | 50 ++++++-------------
 1 file changed, 15 insertions(+), 35 deletions(-)

diff --git a/packages/angular_devkit/build_angular/src/tools/esbuild/external-packages-plugin.ts b/packages/angular_devkit/build_angular/src/tools/esbuild/external-packages-plugin.ts
index fda108b9841c..5d1b550df065 100644
--- a/packages/angular_devkit/build_angular/src/tools/esbuild/external-packages-plugin.ts
+++ b/packages/angular_devkit/build_angular/src/tools/esbuild/external-packages-plugin.ts
@@ -7,9 +7,7 @@
  */
 
 import type { Plugin } from 'esbuild';
-import { extname } from 'node:path';
-
-const EXTERNAL_PACKAGE_RESOLUTION = Symbol('EXTERNAL_PACKAGE_RESOLUTION');
+import { extname, isAbsolute } from 'node:path';
 
 /**
  * Creates a plugin that marks any resolved path as external if it is within a node modules directory.
@@ -34,49 +32,31 @@ export function createExternalPackagesPlugin(options?: { exclude?: string[] }):
         return;
       }
 
-      const loaderFileExtensions = new Set(loaderOptionKeys);
+      const loaderFileExtensions = loaderOptionKeys && new Set(loaderOptionKeys);
 
-      // Only attempt resolve of non-relative and non-absolute paths
+      // esbuild's external packages option considers any package-like path as external
+      // which would exclude paths that are absolute or explicitly relative
       build.onResolve({ filter: /^[^./]/ }, async (args) => {
-        if (args.pluginData?.[EXTERNAL_PACKAGE_RESOLUTION]) {
-          return null;
-        }
-
+        // Skip marking excluded packages
         if (exclusions?.has(args.path)) {
           return null;
         }
 
-        const { importer, kind, resolveDir, namespace, pluginData = {} } = args;
-        pluginData[EXTERNAL_PACKAGE_RESOLUTION] = true;
-
-        const result = await build.resolve(args.path, {
-          importer,
-          kind,
-          namespace,
-          pluginData,
-          resolveDir,
-        });
-
-        // Return result if unable to resolve or explicitly marked external (externalDependencies option)
-        if (!result.path || result.external) {
-          return result;
-        }
-
         // Allow customized loaders to run against configured paths regardless of location
-        if (loaderFileExtensions.has(extname(result.path))) {
-          return result;
+        if (loaderFileExtensions?.has(extname(args.path))) {
+          return null;
         }
 
-        // Mark paths from a node modules directory as external
-        if (/[\\/]node_modules[\\/]/.test(result.path)) {
-          return {
-            path: args.path,
-            external: true,
-          };
+        // Avoid considering Windows absolute paths as package paths
+        if (isAbsolute(args.path)) {
+          return null;
         }
 
-        // Otherwise return original result
-        return result;
+        // Consider the path a package and external
+        return {
+          path: args.path,
+          external: true,
+        };
       });
     },
   };