From 0f1ee90bccc60bc8ef7c92966a371a7a9aa5fc45 Mon Sep 17 00:00:00 2001
From: Charles Lyding <19598772+clydin@users.noreply.github.com>
Date: Thu, 5 Feb 2026 11:22:26 -0500
Subject: [PATCH] fix(@angular/build): correctly resolve absolute setup file
 paths in Vitest

The `resolveId` hook in the Vitest runner plugins now correctly handles absolute paths. Previously, the logic would blindly join the base directory with the file ID, which caused issues when the ID was already a fully qualified absolute path within the workspace. The updated logic now checks if the ID is absolute and located within the base directory before deciding whether to join paths, ensuring compatibility with both absolute paths and Vitest's short-form root-relative paths.
---
 .../src/builders/unit-test/runners/vitest/plugins.ts | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

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 22c5993eabe2..9abe0d7be404 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
@@ -229,7 +229,17 @@ export function createVitestPlugins(pluginOptions: PluginOptions): VitestPlugins
         }
 
         // Construct the full, absolute path and normalize it to POSIX format.
-        const fullPath = toPosixPath(path.join(baseDir, id));
+        let fullPath: string;
+        if (path.isAbsolute(id)) {
+          const relativeId = path.relative(baseDir, id);
+          fullPath =
+            !relativeId.startsWith('..') && !path.isAbsolute(relativeId)
+              ? id
+              : path.join(baseDir, id);
+        } else {
+          fullPath = path.join(baseDir, id);
+        }
+        fullPath = toPosixPath(fullPath);
 
         if (testFileToEntryPoint.has(fullPath)) {
           return fullPath;