From 48f425e14a1b76ba773efbd0546a9e8f34198521 Mon Sep 17 00:00:00 2001
From: Alan Agius <17563226+alan-agius4@users.noreply.github.com>
Date: Fri, 5 Sep 2025 09:03:58 +0000
Subject: [PATCH] fix(@angular/build): preserve names in esbuild for improved
 debugging in dev mode

This commit introduces the `keepNames` option in esbuild configurations for both application code bundling and Vite utility functions.

By setting `keepNames` to `true` (or conditionally based on optimization settings), function and variable names are preserved during the build process. This significantly improves the debugging experience in **development mode** by ensuring that original names are retained in compiled output, leading to more readable stack traces and easier identification of code sections during development.
---
 .../src/tools/esbuild/application-code-bundle.ts     | 12 ++++++++----
 packages/angular/build/src/tools/vite/utils.ts       |  1 +
 .../tests/build/prerender/error-with-sourcemaps.ts   |  2 +-
 3 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/packages/angular/build/src/tools/esbuild/application-code-bundle.ts b/packages/angular/build/src/tools/esbuild/application-code-bundle.ts
index b17029f6c5e1..a19c9a496067 100644
--- a/packages/angular/build/src/tools/esbuild/application-code-bundle.ts
+++ b/packages/angular/build/src/tools/esbuild/application-code-bundle.ts
@@ -607,6 +607,9 @@ function getEsBuildCommonOptions(options: NormalizedApplicationBuildOptions): Bu
     }
   }
 
+  const minifySyntax = optimizationOptions.scripts;
+  const minifyIdentifiers = minifySyntax && allowMangle;
+
   return {
     absWorkingDir: workspaceRoot,
     format: 'esm',
@@ -618,9 +621,10 @@ function getEsBuildCommonOptions(options: NormalizedApplicationBuildOptions): Bu
     metafile: true,
     legalComments: options.extractLicenses ? 'none' : 'eof',
     logLevel: options.verbose && !jsonLogs ? 'debug' : 'silent',
-    minifyIdentifiers: optimizationOptions.scripts && allowMangle,
-    minifySyntax: optimizationOptions.scripts,
-    minifyWhitespace: optimizationOptions.scripts,
+    keepNames: !minifyIdentifiers,
+    minifyIdentifiers,
+    minifySyntax,
+    minifyWhitespace: minifySyntax,
     pure: ['forwardRef'],
     outdir: workspaceRoot,
     outExtension: outExtension ? { '.js': `.${outExtension}` } : undefined,
@@ -637,7 +641,7 @@ function getEsBuildCommonOptions(options: NormalizedApplicationBuildOptions): Bu
       // Only set to false when script optimizations are enabled. It should not be set to true because
       // Angular turns `ngDevMode` into an object for development debugging purposes when not defined
       // which a constant true value would break.
-      ...(optimizationOptions.scripts ? { 'ngDevMode': 'false' } : undefined),
+      ...(minifySyntax ? { 'ngDevMode': 'false' } : undefined),
       'ngJitMode': jit ? 'true' : 'false',
       'ngServerMode': 'false',
       'ngHmrMode': options.templateUpdates ? 'true' : 'false',
diff --git a/packages/angular/build/src/tools/vite/utils.ts b/packages/angular/build/src/tools/vite/utils.ts
index 2322eb210bec..048386a4dc4d 100644
--- a/packages/angular/build/src/tools/vite/utils.ts
+++ b/packages/angular/build/src/tools/vite/utils.ts
@@ -98,6 +98,7 @@ export function getDepOptimizationConfig({
     esbuildOptions: {
       // Set esbuild supported targets.
       target,
+      keepNames: true,
       supported: getFeatureSupport(target, zoneless),
       plugins,
       loader,
diff --git a/tests/legacy-cli/e2e/tests/build/prerender/error-with-sourcemaps.ts b/tests/legacy-cli/e2e/tests/build/prerender/error-with-sourcemaps.ts
index 8e45499f0021..6420f7a6e5c4 100644
--- a/tests/legacy-cli/e2e/tests/build/prerender/error-with-sourcemaps.ts
+++ b/tests/legacy-cli/e2e/tests/build/prerender/error-with-sourcemaps.ts
@@ -48,6 +48,6 @@ export default async function () {
     message,
     // When babel is used it will add names to the sourcemap and `constructor` will be used in the stack trace.
     // This will currently only happen if AOT and script optimizations are set which enables advanced optimizations.
-    /window is not defined[.\s\S]*(?:constructor|_App) \(.*app\.ts\:\d+:\d+\)/,
+    /window is not defined[.\s\S]*(?:constructor|App) \(.*app\.ts\:\d+:\d+\)/,
   );
 }