node:fs.readdir: should not fail even if folder contains self-referen…

…tial symlinks (#10679)

src/bun.js/node/node_fs.zig

@@ -504,6 +504,12 @@ pub const AsyncReaddirRecursiveTask = struct {
                     is_root,
                 )) {
                     .err => |err| {
+                        // readdir() should never fail with 'ELOOP: Too many levels of symbolic links'
+                        if (err.getErrno() == .LOOP) {
+                            this.writeResults(ResultType, &entries);
+                            return;
+                        }
+
                         for (entries.items) |*item| {
                             switch (ResultType) {
                                 bun.String => item.deref(),
@@ -4967,6 +4973,8 @@ pub const NodeFS = struct {
                         // This is different than what Node does, at the time of writing.
                         // Node doesn't gracefully handle errors like these. It fails the entire operation.
                         .NOENT, .NOTDIR, .PERM => continue,
+                        // readdir() should never fail with 'ELOOP: Too many levels of symbolic links'
+                        .LOOP => continue,
                         else => {
                             const path_parts = [_]string{ args.path.slice(), basename };
                             return .{

test/js/node/fs/fixtures/readdir-loop/a/b/c/d/e/f

@@ -0,0 +1 @@
+../../../..

test/js/node/fs/fs.test.ts

@@ -8,6 +8,7 @@ import fs, {
   existsSync,
   mkdirSync,
   openSync,
+  readdir,
   readdirSync,
   readFile,
   readFileSync,
@@ -3030,3 +3031,20 @@ it("promises.fdatasync with a bad fd should include that in the error thrown", a
   }
   expect.unreachable();
 });
+
+it("readdirSync should not crash on symlink loops", () => {
+  // prettier-ignore
+  expect(readdirSync(join(import.meta.dirname, "./fixtures/readdir-loop"), { recursive: true }).length).toBe(symlink_fixture_depth());
+});
+
+it("readdir should not crash on symlink loops", async () => {
+  // prettier-ignore
+  expect((await promisify(readdir)(join(import.meta.dirname, "./fixtures/readdir-loop"), { recursive: true })).length).toBe(symlink_fixture_depth());
+});
+
+function symlink_fixture_depth() {
+  if (process.platform === "darwin") return 166;
+  if (process.platform === "linux") return 206;
+  if (process.platform === "win32") return 6;
+  throw new Error(`test unimplemented for '${process.platform}'`);
+}