When do you write project documentation?

Question

Programming

Important: This is not about documentation in the code, but about the entire project as a whole (how to use, how to configure)
There are two options:
In the process of writing:
Write the docks together with the code describing every little thing. If some feature changes, you will rewrite the documentation.
After writing the project:
You carefully follow the finished project, learn Zen and sit down to write docks.
PS It is desirable to argue your opinion ...

Answer 1

The documentation is not only for show, but also to help you, which means the second option is just idiocy. If the project is large, by the time it is completed, you will simply remember what this or that method does. So only the first option. The second is acceptable if this is a very small project and the documentation is stupid for a daw.
I'm already silent that the correct documentation and a modern IDE help in the process with stupid auto-completions and quick navigation.