feat(vfs): add @scratchyjs/vfs private in-memory filesystem package

packages/vfs/package.json

@@ -0,0 +1,16 @@
+{
+  "name": "@scratchyjs/vfs",
+  "version": "1.0.0",
+  "private": true,
+  "type": "module",
+  "exports": {
+    ".": "./src/index.ts"
+  },
+  "scripts": {
+    "typecheck": "tsc --noEmit"
+  },
+  "devDependencies": {
+    "@types/node": "22.16.0",
+    "typescript": "5.8.3"
+  }
+}

packages/vfs/src/errors.ts

@@ -0,0 +1,92 @@
+/**
+ * POSIX-style filesystem error helpers for the virtual file system.
+ *
+ * Each helper creates a standard {@link NodeJS.ErrnoException} with the
+ * appropriate `code`, `syscall`, and (where applicable) `path` properties.
+ * This mirrors the error shapes produced by the real `node:fs` module so that
+ * callers can use the same `err.code === 'ENOENT'` checks they already rely on.
+ */
+
+function makeError(
+  code: string,
+  message: string,
+  syscall: string,
+  path?: string,
+): NodeJS.ErrnoException {
+  const err: NodeJS.ErrnoException = new Error(
+    `${syscall}: ${message}${path !== undefined ? `, ${syscall} '${path}'` : ""}`,
+  );
+  err.code = code;
+  err.syscall = syscall;
+  if (path !== undefined) {
+    err.path = path;
+  }
+  return err;
+}
+
+export function createENOENT(
+  syscall: string,
+  path: string,
+): NodeJS.ErrnoException {
+  return makeError("ENOENT", "no such file or directory", syscall, path);
+}
+
+export function createENOTDIR(
+  syscall: string,
+  path: string,
+): NodeJS.ErrnoException {
+  return makeError("ENOTDIR", "not a directory", syscall, path);
+}
+
+export function createENOTEMPTY(
+  syscall: string,
+  path: string,
+): NodeJS.ErrnoException {
+  return makeError("ENOTEMPTY", "directory not empty", syscall, path);
+}
+
+export function createEISDIR(
+  syscall: string,
+  path: string,
+): NodeJS.ErrnoException {
+  return makeError("EISDIR", "illegal operation on a directory", syscall, path);
+}
+
+export function createEBADF(syscall: string): NodeJS.ErrnoException {
+  return makeError("EBADF", "bad file descriptor", syscall);
+}
+
+export function createEEXIST(
+  syscall: string,
+  path: string,
+): NodeJS.ErrnoException {
+  return makeError("EEXIST", "file already exists", syscall, path);
+}
+
+export function createEROFS(
+  syscall: string,
+  path: string,
+): NodeJS.ErrnoException {
+  return makeError("EROFS", "read-only file system", syscall, path);
+}
+
+export function createEINVAL(
+  syscall: string,
+  path: string,
+): NodeJS.ErrnoException {
+  return makeError("EINVAL", "invalid argument", syscall, path);
+}
+
+export function createELOOP(
+  syscall: string,
+  path: string,
+): NodeJS.ErrnoException {
+  return makeError("ELOOP", "too many levels of symbolic links", syscall, path);
+}
+
+export function createEACCES(
+  syscall: string,
+  path: string,
+): NodeJS.ErrnoException {
+  return makeError("EACCES", "permission denied", syscall, path);
+}