fix: tighten path guard coverage

src/infra/path-guards.test.ts

@@ -1,4 +1,4 @@
-import { describe, expect, it } from "vitest";
+import { afterEach, describe, expect, it } from "vitest";
 import {
   hasNodeErrorCode,
   isNodeError,
@@ -8,6 +8,21 @@ import {
   normalizeWindowsPathForComparison,
 } from "./path-guards.js";
 
+const originalPlatformDescriptor = Object.getOwnPropertyDescriptor(process, "platform");
+
+function setPlatform(platform: NodeJS.Platform): void {
+  Object.defineProperty(process, "platform", {
+    value: platform,
+    configurable: true,
+  });
+}
+
+afterEach(() => {
+  if (originalPlatformDescriptor) {
+    Object.defineProperty(process, "platform", originalPlatformDescriptor);
+  }
+});
+
 describe("normalizeWindowsPathForComparison", () => {
   it("normalizes extended-length and UNC windows paths", () => {
     expect(normalizeWindowsPathForComparison("\\\\?\\C:\\Users\\Peter/Repo")).toBe(
@@ -47,4 +62,19 @@ describe("isPathInside", () => {
     expect(isPathInside("/workspace/root", "/workspace/root/nested/file.txt")).toBe(true);
     expect(isPathInside("/workspace/root", "/workspace/root/../escape.txt")).toBe(false);
   });
+
+  it("uses win32 path semantics for windows containment checks", () => {
+    setPlatform("win32");
+
+    expect(isPathInside(String.raw`C:\workspace\root`, String.raw`C:\workspace\root`)).toBe(true);
+    expect(
+      isPathInside(String.raw`C:\workspace\root`, String.raw`C:\workspace\root\Nested\File.txt`),
+    ).toBe(true);
+    expect(
+      isPathInside(String.raw`C:\workspace\root`, String.raw`C:\workspace\root\..\escape.txt`),
+    ).toBe(false);
+    expect(
+      isPathInside(String.raw`C:\workspace\root`, String.raw`D:\workspace\root\file.txt`),
+    ).toBe(false);
+  });
 });

src/infra/path-guards.ts

@@ -33,16 +33,15 @@ export function isSymlinkOpenError(value: unknown): boolean {
 }
 
 export function isPathInside(root: string, target: string): boolean {
-  const resolvedRoot = path.resolve(root);
-  const resolvedTarget = path.resolve(target);
-
   if (process.platform === "win32") {
-    const rootForCompare = normalizeWindowsPathForComparison(resolvedRoot);
-    const targetForCompare = normalizeWindowsPathForComparison(resolvedTarget);
+    const rootForCompare = normalizeWindowsPathForComparison(path.win32.resolve(root));
+    const targetForCompare = normalizeWindowsPathForComparison(path.win32.resolve(target));
     const relative = path.win32.relative(rootForCompare, targetForCompare);
     return relative === "" || (!relative.startsWith("..") && !path.win32.isAbsolute(relative));
   }
 
+  const resolvedRoot = path.resolve(root);
+  const resolvedTarget = path.resolve(target);
   const relative = path.relative(resolvedRoot, resolvedTarget);
   return relative === "" || (!relative.startsWith("..") && !path.isAbsolute(relative));
 }