different-ai/openwork · error · InterpreterRuntimeError

Generator functions are not supported in CodeMode.

Error message

Generator functions are not supported in CodeMode.

What it means

Generator functions (function* and yield) are not implemented in CodeMode. createFunction checks node.generator and throws an UnsupportedSyntax error before any code runs. The interpreter supports only ordinary function declarations/expressions and arrow functions.

Source

Thrown at packages/codemode/src/interpreter/runtime.ts:855

        const result = yield* self.evaluateStatement(statement)

        if (result.kind === "value") {
          self.lastValue = result.value
          continue
        }

        if (result.kind !== "none") {
          return result
        }
      }

      return { kind: "none" } satisfies StatementResult
    }).pipe(Effect.ensuring(Effect.sync(() => self.popScope())))
  }

  private createFunction(node: AstNode): CodeModeFunction {
    if (node.generator === true) {
      throw new InterpreterRuntimeError(
        "Generator functions are not supported in CodeMode.",
        node,
        "UnsupportedSyntax",
        [supportedSyntaxMessage],
      )
    }
    return new CodeModeFunction(
      getArray(node, "params").map((parameter, index) => asNode(parameter, `params[${index}]`)),
      getNode(node, "body"),
      this.scopes.slice(),
    )
  }

  // Function declarations are hoisted: bound in their scope before the body runs, so a
  // program can call a helper defined further down (matching JavaScript).
  private hoistFunctions(statements: Array<unknown>): void {
    for (const statementValue of statements) {
      if (!isRecord(statementValue) || statementValue.type !== "FunctionDeclaration") continue

View on GitHub (pinned to 2b7df46e8a)

Solutions

1. Rewrite the generator as a function returning a plain array of results
2. Replace lazy iteration with eager computation using loops
3. If the sequence is huge, process it in chunks with supported loop syntax or use a host tool

Example fix

// before
function* range(n) { for (let i = 0; i < n; i++) yield i; }
const vals = [...range(5)];
// after
function range(n) { const out = []; for (let i = 0; i < n; i++) out.push(i); return out; }
const vals = range(5);

if (/function\s*\*/.test(code) || /\byield\b/.test(code)) {
  throw new Error('Generators (function*/yield) are unsupported in CodeMode; return arrays instead');
}

function usesGeneratorSyntax(code) { return /function\s*\*/.test(code) || /\byield\b/.test(code); }

When it happens

Trigger: Declaring function* gen() {...} or an async generator inside CodeMode code; createFunction is reached via hoistFunctions (top-level declarations) or evaluateExpression (function expressions, IIFEs).

Common situations: Porting iterator/generator-based utilities into sandboxed code; LLM-generated code that lazily produces sequences with generators; using yield for cooperative iteration patterns.

Related errors

• Array.from(...) does not support a map function in CodeMode;
• for await...of is not supported.
• Expected '${key}' to be a boolean.
• Failed to parse script as a Program node.
• String.${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/593e8516dbffd539. Report an issue: GitHub.