simpleeval: distinguish a missing module from an invalid expression

The import and the expression are separate

The simpleeval project describes constrained expression evaluation, including exposed names, functions and resource limits.1 A missing module is not the same as a rejected expression.

python -m pip show simpleeval

Our suggested investigation starts by preserving the original node, expression, input values and exception. For a missing package, follow the node's dependency declaration. For an unknown name or function, check what that node actually exposes to its evaluator.

In a copy, reduce the expression to one known input, then restore one operation at a time. This is a diagnostic method, not a claim that every node supports the same expression language.

Do not replace a constrained evaluator with unrestricted Python eval or remove computational limits to make a shared workflow run. Validate the expected output type and result before reconnecting the node to the larger workflow. Replacing the original expression with an unrelated constant is only a smoke test, not a completed repair.

Related checks

• No module named yaml, PIL or pydantic_settings: check the distribution name
• Keep a reproducible ComfyUI repair record without exposing secrets

Research draft. No local/GPU reproduction or independent editorial sign-off. Upstream statements and our recommendations are distinguished.