refactor(filesystem): add unit tests and change of joinPath implementation

Author: cyfung1031

packages/filesystem/utils.test.ts

@@ -0,0 +1,43 @@
+import { describe, expect, it } from "vitest";
+import { joinPath } from "./utils";
+
+describe("joinPath", () => {
+  it("joins relative path segments as an absolute normalized path", () => {
+    expect(joinPath("path1", "path2")).toBe("/path1/path2");
+  });
+
+  it("does not create duplicate slashes when segments already contain slashes", () => {
+    expect(joinPath("/path1", "/path2")).toBe("/path1/path2");
+    expect(joinPath("/path1/", "/path2/")).toBe("/path1/path2");
+    expect(joinPath("path1/", "path2/")).toBe("/path1/path2");
+    expect(joinPath("/path1/", "path2")).toBe("/path1/path2");
+  });
+
+  it("keeps root-relative behavior when the first segment is empty", () => {
+    expect(joinPath("", "file.txt")).toBe("/file.txt");
+    expect(joinPath("", "dir", "file.txt")).toBe("/dir/file.txt");
+  });
+
+  it("handles root path segments", () => {
+    expect(joinPath("/", "file.txt")).toBe("/file.txt");
+    expect(joinPath("/", "dir", "file.txt")).toBe("/dir/file.txt");
+  });
+
+  it("skips empty path segments", () => {
+    expect(joinPath("dir", "", "file.txt")).toBe("/dir/file.txt");
+    expect(joinPath("", "dir", "", "file.txt", "")).toBe("/dir/file.txt");
+  });
+
+  it("returns empty string when no meaningful path is provided", () => {
+    expect(joinPath()).toBe("");
+    expect(joinPath("")).toBe("");
+    expect(joinPath("", "")).toBe("");
+    expect(joinPath("/")).toBe("");
+    expect(joinPath("/", "")).toBe("");
+  });
+
+  it("normalizes multiple adjacent slashes inside segments", () => {
+    expect(joinPath("//path1//", "//path2//")).toBe("/path1/path2");
+    expect(joinPath("path1//nested", "path2")).toBe("/path1/nested/path2");
+  });
+});

packages/filesystem/utils.ts

@@ -1,18 +1,25 @@
 export function joinPath(...paths: string[]): string {
-  let path = "";
-  for (let value of paths) {
-    if (!value) {
+  let result = "";
+
+  for (const path of paths) {
+    if (!path) {
       continue;
     }
-    if (!value.startsWith("/")) {
-      if (path) {
-        value = `/${value}`;
+
+    let start = 0;
+
+    for (let i = 0; i <= path.length; i++) {
+      if (i !== path.length && path[i] !== "/") {
+        continue;
       }
+
+      if (i > start) {
+        result += `/${path.slice(start, i)}`;
+      }
+
+      start = i + 1;
     }
-    if (value.endsWith("/")) {
-      value = value.substring(0, value.length - 1);
-    }
-    path += value;
   }
-  return path;
+
+  return result;
 }