fix: Adjusted url join to avoid double slashes

src/resolve.ts

@@ -122,7 +122,7 @@ function _resolve(id: string | URL, options: ResolveOptions = {}): string {
     for (const prefix of ["", "/index"]) {
       for (const extension of options.extensions || DEFAULT_EXTENSIONS) {
         resolved = _tryModuleResolve(
-          id + prefix + extension,
+          joinURL(id, prefix) + extension,
           url,
           conditionsSet,
         );

test/resolve.test.ts

@@ -1,6 +1,7 @@
 import { existsSync } from "node:fs";
-import { describe, it, expect } from "vitest";
+import { describe, it, expect, vi, afterEach } from "vitest";
 import { resolveSync, resolvePathSync, fileURLToPath } from "../src";
+import { parseFilename } from "ufo";
 
 const tests = [
   // Resolve to path
@@ -14,6 +15,44 @@ const tests = [
   { input: "/non/existent", action: "throws" },
 ] as const;
 
+afterEach(() => {
+  vi.restoreAllMocks();
+});
+
+const { mockedResolve } = await vi.hoisted(async () => {
+  const importMetaResolve = await vi.importActual<
+    Record<string, (...args: unknown[]) => unknown>
+  >("import-meta-resolve");
+  return {
+    mockedResolve: vi.fn((id, url, conditions) => {
+      return importMetaResolve.moduleResolve(id, url, conditions);
+    }),
+  };
+});
+
+vi.mock("import-meta-resolve", () => {
+  return {
+    moduleResolve: mockedResolve,
+  };
+});
+
+describe("tryModuleResolve", () => {
+  it("should create correct url", () => {
+    expect(() =>
+      resolvePathSync("tslib/", {
+        url: import.meta.url.replace(
+          parseFilename(import.meta.url, { strict: false }) || "",
+          "",
+        ),
+      }),
+    ).toThrow();
+    expect(mockedResolve).toHaveBeenCalled();
+    expect(
+      mockedResolve.mock.calls.some((call) => call[0].includes("//")),
+    ).toBe(false);
+  });
+});
+
 describe("resolveSync", () => {
   for (const test of tests) {
     it(`${test.input} should ${test.action}`, () => {