microsoft/autogen · error · ValueError

Could not compile function: {e}

Error message

Could not compile function: {e}

What it means

FunctionWithRequirementsStr executes your source string as a module (spec.loader.exec_module) at construction time and wraps any exception raised during execution — syntax errors, missing imports, or top-level runtime errors — in ValueError('Could not compile function: <original error>'). The original exception is chained (`from e`), so the full traceback of your actual mistake is preserved one level down.

Source

Thrown at python/packages/autogen-core/src/autogen_core/code_executor/_func_with_reqs.py:117

    def __init__(self, func: str, python_packages: Sequence[str] = [], global_imports: Sequence[Import] = []):
        self.func = func
        self.python_packages = python_packages
        self.global_imports = global_imports

        module_name = "func_module"
        loader = _StringLoader(func)
        spec = spec_from_loader(module_name, loader)
        if spec is None:
            raise ValueError("Could not create spec")
        module = module_from_spec(spec)
        if spec.loader is None:
            raise ValueError("Could not create loader")

        try:
            spec.loader.exec_module(module)
        except Exception as e:
            raise ValueError(f"Could not compile function: {e}") from e

        functions = inspect.getmembers(module, inspect.isfunction)
        if len(functions) != 1:
            raise ValueError("The string must contain exactly one function")

        self._func_name, self.compiled_func = functions[0]

    def __call__(self, *args: Any, **kwargs: Any) -> None:
        raise NotImplementedError("String based function with requirement objects are not directly callable")


@dataclass
class FunctionWithRequirements(Generic[T, P]):
    func: Callable[P, T]
    python_packages: Sequence[str] = field(default_factory=list)
    global_imports: Sequence[Import] = field(default_factory=list)

    @classmethod

View on GitHub (pinned to 027ecf0a37)

Solutions

1. Read the chained exception (`e.__cause__`) — it contains the real SyntaxError/ModuleNotFoundError with line info.
2. Install the imported packages in the local environment or vendor the imports lazily inside the function body.
3. Validate the string first: `compile(func_string, '<func>', 'exec')` catches syntax errors cheaply before constructing.
4. Keep the string to exactly one function with no top-level executable code besides imports/defs.

Example fix

# before
f = FunctionWithRequirementsStr(
    "def transform(x):\n    import numpy as np\n    return np.array(x)",
    python_packages=["numpy"],
)  # ValueError: Could not compile function: ModuleNotFoundError: numpy (if numpy missing locally)

# after (import only what exists locally, or install numpy first)
f = FunctionWithRequirementsStr(
    "def transform(x):\n    return [float(v) for v in x]",
    python_packages=[],
)

def compiles_cleanly(source: str) -> bool:
    try:
        compile(source, "<func>", "exec")
        return True
    except SyntaxError:
        return False

assert compiles_cleanly(func_string)

try:
    f = FunctionWithRequirementsStr(src)
except ValueError as e:
    cause = e.__cause__  # the real SyntaxError / ModuleNotFoundError
    raise RuntimeError(f"function string failed to load: {cause}") from cause

When it happens

Trigger: Passing a string whose code imports a package not installed in the current process (`import numpy` without numpy), has a syntax error, or raises at module level (e.g. a constant computed by calling something undefined). Note: the import runs in YOUR interpreter, not in the later code-execution sandbox.

Common situations: Listing packages in python_packages=['numpy'] for the remote executor while numpy is absent locally; LLM- or template-generated code strings with typos; strings copied from files with smart quotes or indentation damage.

Related errors

• The string must contain exactly one function
• String based function with requirement objects are not direc
• Could not create spec
• Could not create loader
• Message type not found

AI-assisted analysis of microsoft/autogen@027ecf0a37 (2026-08-15). Data as JSON: /api/errors/b1687b48b592797c. Report an issue: GitHub.