denoland/deno · error · ERR_INVALID_ARG_VALUE

ERR_INVALID_ARG_VALUE

ERR_INVALID_ARG_VALUE

Error message

The property 'options.version' must be "preview1" or "unstable". Received ${options.version}

What it means

Thrown by the WASI constructor when options.version is present but is neither "preview1" nor "unstable". These two strings select the WASI snapshot (wasi_snapshot_preview1 vs wasi_unstable) that determines which import object the instance exposes. Any other value, including newer names like "preview2", is rejected.

Source

Thrown at ext/node/polyfills/wasi.ts:157

  #ctx;
  #version: string;
  #started = false;
  #returnOnExit: boolean;
  #wasiImport;

  constructor(options?: WasiOptions) {
    emitExperimentalWarning();
    if (options === undefined) {
      throw new ERR_INVALID_ARG_TYPE("options.version", "string", undefined);
    }
    validateObject(options, "options");

    if (options.version === undefined) {
      throw new ERR_INVALID_ARG_TYPE("options.version", "string", undefined);
    }
    validateString(options.version, "options.version");
    if (options.version !== "preview1" && options.version !== "unstable") {
      throw new ERR_INVALID_ARG_VALUE(
        "options.version",
        options.version,
        'must be "preview1" or "unstable"',
      );
    }

    const argsValue = options.args ?? [];
    if (options.args !== undefined) {
      validateArray(options.args, "options.args");
    }
    const args = ArrayPrototypeMap(argsValue, (arg) => String(arg));

    const envObj = options.env ?? {};
    if (options.env !== undefined) {
      validateObject(options.env, "options.env");
    }
    const envPairs: [string, string][] = [];
    for (const entry of new SafeArrayIterator(ObjectEntries(envObj))) {

View on GitHub (pinned to 9ad36f7a2c)

Solutions

1. Set `version: "preview1"` — this is the value virtually all command-line wasm modules built with wasi-sdk/clang --target=wasi32-wasi use.
2. If you need reactorthreaded modules documented as 'unstable', use `version: "unstable"`.
3. Do not feed preview2 component strings into this API; use a preview2-capable runtime or compile the module with the preview1 adapter instead.

Example fix

// before
const wasi = new WASI({ version: "preview2" });

// after
const wasi = new WASI({ version: "preview1" });

const VALID_WASI_VERSIONS = new Set(['preview1', 'unstable']);
if (!VALID_WASI_VERSIONS.has(userVersion)) {
  throw new Error(`Unsupported WASI version ${userVersion}; use "preview1"`);
}

function isWasiVersion(v: unknown): v is 'preview1' | 'unstable' {
  return v === 'preview1' || v === 'unstable';
}

When it happens

Trigger: `new WASI({ version: "preview2" })` (WASI preview2 is a different API and not accepted here), `version: "latest"`, a typo like "preivew1", or a version string read from an env var / package.json that uses different naming.

Common situations: Assuming the Node WASI API supports WASI preview2 (it does not — preview2 is component-model based and served by separate runtimes); upgrading a toolchain that emits a different version string; sharing one config between a Wasmtime embedder and the Node API.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• ERR_INVALID_ARG_TYPE
• ERR_WASI_NOT_STARTED
• ERR_WASI_ALREADY_STARTED
• ERR_TLS_ALPN_CALLBACK_WITH_PROTOCOLS
• UVWASI_ENOENT

AI-assisted analysis of denoland/deno@9ad36f7a2c (2026-08-20). Data as JSON: /api/errors/22ce059072d674ac. Report an issue: GitHub.