different-ai/openwork · error · InterpreterRuntimeError

Array.from(...) does not support a map function in…

Error message

Array.from(...) does not support a map function in CodeMode; call .map() on the result instead.

What it means

CodeMode supports Array.from only for converting an array-like/iterable into an array. The two-argument form where the second parameter is a mapping function is deliberately rejected with an UnsupportedSyntax error, directing developers to chain .map() separately. This keeps the interpreter's implementation surface small and error hints actionable.

Solutions

Call Array.from with a single argument, then chain .map() on the result
Build the values with a supported loop or Array constructor pattern
If mapping a range, use a supported helper or a for loop pushing into an array

Example fix

// before
const squares = Array.from({length: 5}, (_, i) => i * i);
// after
const squares = Array.from({length: 5}).map((_, i) => i * i);

Defensive patterns

Strategy: validation

Validate before calling

// Reject two-argument Array.from before running CodeMode
if (/Array\.from\s*\([^)]*,/.test(code)) {
  throw new Error('CodeMode code uses Array.from with a map function; use .map() instead');
}

Type guard

function isSingleArgArrayFrom(call) { return call.arguments.length === 1; }

Prevention

Always call Array.from with exactly one argument in sandbox code
Chain .map() after Array.from for transformations
Add a pre-execution lint rule for the Array.from(x, fn) pattern

When it happens

Trigger: Calling Array.from(iterable, mapFn) with more than one argument inside CodeMode, e.g. Array.from({length: 5}, (_, i) => i * 2) or Array.from(str, ch => ch.toUpperCase()).

Common situations: Idiomatic JS one-liners ported into CodeMode; LLM-generated code that uses the mapFn overload; refactoring existing scripts into sandboxed code without adapting Array.from usage.

Related errors

AI-assisted analysis of different-ai/openwork@2b7df46e8a (2026-09-01). Data as JSON: /api/errors/0a2bfa9065d466cd. Report an issue: GitHub.

Appendix: source

Thrown at packages/codemode/src/interpreter/runtime.ts:520

    case "concat": {
      result = value.concat(...args.map((_, index) => str(index)))
      break
    }
    default:
      throw new InterpreterRuntimeError(`String method '${name}' is not available in CodeMode.`, node)
  }
  return boundedData(result, `String.${name} result`)
}

const invokeArrayStatic = (name: string, args: Array<unknown>, node: AstNode): unknown => {
  switch (name) {
    case "isArray":
      return Array.isArray(args[0])
    case "of":
      return [...args]
    case "from": {
      if (args.length > 1) {
        throw new InterpreterRuntimeError(
          "Array.from(...) does not support a map function in CodeMode; call .map() on the result instead.",
          node,
          "UnsupportedSyntax",
          [supportedSyntaxMessage],
        )
      }
      // Map/Set materialize directly (the data checkpoint would serialize them to {}).
      if (args[0] instanceof SandboxMap)
        return Array.from((args[0] as SandboxMap).map.entries(), ([key, item]) => [key, item])
      if (args[0] instanceof SandboxSet) return Array.from((args[0] as SandboxSet).set.values())
      if (args[0] instanceof SandboxURLSearchParams) {
        return Array.from(args[0].params.entries(), ([key, value]) => [key, value])
      }
      const source = boundedData(args[0], "Array.from input")
      if (typeof source === "string") return Array.from(source)
      if (Array.isArray(source)) return [...source]
      if (
        source !== null &&

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