predict create erroneous prediction if you use input created from formula (or edit domain or random data) about orange3 HOT 3 CLOSED

This is actually not a bug, although it can be very confusing. Maybe there is some additional warning that could guide users to a solution.

What happens is that Formula (and some other transformations) create a new variable that can have the same name, but is not the same object. As you noted, they have a different compute_value.
When Orange tries to use a dataset for predictions it checks that the variables are the same as the data the model was trained on. It can't just match the variables by names, because a normalized columns is not the same as the original one for example.

To tell Orange to forget about transformations (the compute_value) and "reset" a variable (=same effect as saving the data to a file and reading it again), you can use Edit Domain: select the variable and check "Unlink variable from its source variable".
The tooltip provides this explanation:

Make Orange forget that the variable is derived from another.
Use this for instance when you want to consider variables with the same name but from different sources as the same variable.

from orange3.

Thank you. Can I submit a pull request to display the warning?

from orange3.

Sure. But before you spend too much time preparing the PR, maybe propose a suggestion where and when you would show the warning so we can discuss the solution.

from orange3.