different-ai/openwork · error · InterpreterRuntimeError

Object.assign expects data objects.

Error message

Object.assign expects data objects.

What it means

The Object.assign branch validates every source argument is a plain data object (not null, undefined — those are skipped — not array, not primitive, not sandbox value) and throws this when a source fails the check, matching the assign-specific requireObject semantics.

Source

Thrown at packages/codemode/src/stdlib/object.ts:45

      if (value === null || typeof value !== "object") {
        throw new InterpreterRuntimeError("Object.keys expects a data object or array.", node)
      }
      return Object.keys(value)
    }
    case "values":
      return Object.values(requireObject())
    case "entries":
      return Object.entries(requireObject()).map(([key, item]) => [key, item])
    case "hasOwn":
      return Object.hasOwn(requireObject(), String(args[1]))
    case "assign": {
      const out: Record<string, unknown> = Object.create(null)
      for (const source of args) {
        if (source === null || source === undefined) continue
        const value = boundedData(source, "Object.assign input")
        if (isSandboxValue(value)) continue
        if (value === null || typeof value !== "object" || Array.isArray(value)) {
          throw new InterpreterRuntimeError("Object.assign expects data objects.", node)
        }
        for (const [key, item] of Object.entries(value)) guardedSet(out, key, item)
      }
      return out
    }
    case "fromEntries": {
      if (args[0] instanceof SandboxMap) {
        const out: Record<string, unknown> = Object.create(null)
        for (const [key, item] of args[0].map.entries()) guardedSet(out, coerceToString(key), item)
        return out
      }
      if (args[0] instanceof SandboxURLSearchParams) {
        const out: Record<string, unknown> = Object.create(null)
        for (const [key, value] of args[0].params.entries()) guardedSet(out, key, value)
        return out
      }
      const pairs = boundedData(args[0], "Object.fromEntries input")
      if (!Array.isArray(pairs)) {

View on GitHub (pinned to 2b7df46e8a)

Solutions

1. Wrap array sources: Object.assign({}, ...arr) → iterate and index-convert first, or Object.fromEntries(arr.map((v,i)=>[String(i),v]))
2. Skip/normalize scalar sources before merging: const src = (v) => (v && typeof v === 'object' && !Array.isArray(v) ? v : {})
3. Check the producing function/endpoint for a shape change and fix at the source
4. Merge only after validating each input with a plain-object check

Example fix

// before
const merged = Object.assign({}, defaults, apiResult)
// after
const src = apiResult && typeof apiResult === 'object' && !Array.isArray(apiResult) ? apiResult : {}
const merged = Object.assign({}, defaults, src)

const asPlainObject = (v: unknown): Record<string, unknown> =>
  v !== null && typeof v === 'object' && !Array.isArray(v) ? v as Record<string, unknown> : {}
const merged = Object.assign({}, asPlainObject(defaults), asPlainObject(apiResult))

const isMergeSource = (v: unknown): v is Record<string, unknown> =>
  v !== null && v !== undefined && typeof v === 'object' && !Array.isArray(v)

try {
  return Object.assign({}, source)
} catch (e) {
  if (e instanceof InterpreterRuntimeError && e.message.includes('Object.assign expects data objects')) {
    return Object.assign({}, normalizeSource(source))
  }
  throw e
}

When it happens

Trigger: Object.assign({}, [1,2]) (array source), Object.assign({}, 42), Object.assign({}, 'str'), Object.assign(target, someArrayResponse) where an upstream call returned an array instead of an object.

Common situations: Merging defaults with an API result that is occasionally an array; spreading array-likes into config; a renamed endpoint changed the response shape from object to list.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

• Object.${name} expects a data object.
• Object.keys expects a data object or array.
• Object.fromEntries expects an array of [key, value] pairs.
• Object.fromEntries expects [key, value] pairs.
• String.${name} expects argument ${index + 1} to be a number.

AI-assisted analysis of different-ai/openwork@2b7df46e8a (2026-09-01). Data as JSON: /api/errors/6f312a7e593b0c67. Report an issue: GitHub.