From cca84621761d28085c720137a7e5c0b72cbb147c Mon Sep 17 00:00:00 2001
From: Charles Lyding <19598772+clydin@users.noreply.github.com>
Date: Fri, 14 Nov 2025 12:19:58 -0500
Subject: [PATCH] fix(@angular/build): enhance Vitest resolution for optimal
 package loading

Align Vitest's module resolution with the development server to ensure consistent behavior.
This change configures Vitest to prioritize ESM-optimized package entry points by
setting 'es2020', 'module', and 'main' as main fields and 'es2015', 'es2020', and 'module'
as conditions during module resolution. This improves compatibility and performance
by utilizing modern JavaScript module formats where available.
---
 .../build/src/builders/unit-test/runners/vitest/plugins.ts    | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/packages/angular/build/src/builders/unit-test/runners/vitest/plugins.ts b/packages/angular/build/src/builders/unit-test/runners/vitest/plugins.ts
index 5255ef519fec..fada9089d84f 100644
--- a/packages/angular/build/src/builders/unit-test/runners/vitest/plugins.ts
+++ b/packages/angular/build/src/builders/unit-test/runners/vitest/plugins.ts
@@ -124,6 +124,10 @@ export async function createVitestConfigPlugin(
           noDiscovery: true,
           include: options.optimizeDepsInclude,
         },
+        resolve: {
+          mainFields: ['es2020', 'module', 'main'],
+          conditions: ['es2015', 'es2020', 'module'],
+        },
       };
 
       const { optimizeDeps, resolve } = config;