Fix the path separators returned by resolveImport

src/resolve-import.ts

@@ -1,9 +1,12 @@
+import { sep } from "node:path";
 import ts from "typescript";
 import type { CompilerOptions } from "typescript";
 
 /**
  * Given a file name, an imported path, and a TSConfig object, produce a path to the imported file, relative to TypeScript's `baseUrl`.
  *
+ * The resulting path uses OS-appropriate path separators.
+ *
  * @example
  * ```tsx
  * // ./src/pages/home/ui/HomePage.tsx
@@ -41,16 +44,18 @@ export function resolveImport(
   directoryExists?: (path: string) => boolean,
 ): string | null {
   return (
-    ts.resolveModuleName(
-      importedPath,
-      importerPath,
-      normalizeCompilerOptions(tsCompilerOptions),
-      {
-        ...ts.sys,
-        fileExists,
-        directoryExists,
-      },
-    ).resolvedModule?.resolvedFileName ?? null
+    ts
+      .resolveModuleName(
+        importedPath,
+        importerPath,
+        normalizeCompilerOptions(tsCompilerOptions),
+        {
+          ...ts.sys,
+          fileExists,
+          directoryExists,
+        },
+      )
+      .resolvedModule?.resolvedFileName?.replaceAll("/", sep) ?? null
   );
 }
 

src/specs/resolve-import.spec.ts

@@ -1,5 +1,6 @@
 import { expect, test } from "vitest";
 import { resolveImport } from "../index.js";
+import { join } from "node:path";
 
 test("Basic", () => {
   const tsCompilerOptions = {
@@ -21,7 +22,7 @@ test("Basic", () => {
       tsCompilerOptions,
       fileExists,
     ),
-  ).toBe("src/shared/ui/index.ts");
+  ).toBe(join("src", "shared", "ui", "index.ts"));
 });
 
 test("With deprecated moduleResolution: node", () => {
@@ -44,7 +45,7 @@ test("With deprecated moduleResolution: node", () => {
       tsCompilerOptions,
       fileExists,
     ),
-  ).toBe("src/shared/ui/index.ts");
+  ).toBe(join("src", "shared", "ui", "index.ts"));
 });
 
 test("Alias to absolute paths (for whatever reason)", () => {
@@ -65,5 +66,5 @@ test("Alias to absolute paths (for whatever reason)", () => {
       tsCompilerOptions,
       fileExists,
     ),
-  ).toBe("/src/shared/ui/Button.ts");
+  ).toBe(join("/", "src", "shared", "ui", "Button.ts"));
 });