Reuse namespaces

[gchenfc]

Currently, I believe the wrapper will break if you open, close, then reopen a namespace. For example:

namespace ns {
  int a = 5;
}

namespace ns {
  int b = 6;
}

Since the wrapper is not smart enough to realize that these are the same and hence it doesn't have to redefine the submodule pybind11::module m_ns = ....

Aside from minor inconveniences of writing a .i file to remember to put all the stuff from a namespace at the same place, this causes issues using combine_interface_headers which just copy-pastes the contents together. Thus if you want to "add" to a namespace from a different interface header, it won't work.

Not sure whether or not the goal of having a nice pybind way to #include other .i files would be able to handle this, or if we just need some intelligent way of keeping track which namespaces have been handled. For example, a 2-pass approach: first go through all the namespaces and just define them and keep a set() of defined namespaces, then second pass do all the "real" wrapping.

[ProfFan]

We are going one step at a time towards a real C++ compiler in Python... 🤣

[gchenfc]

lol ikr 😂

[varunagrawal]

*transpiler

[varunagrawal]

Jokes aside, this is solvable via a 2 pass compiler rather than the current 1 pass compiler scheme. Though this would have come up when fixing #44 which I believe is what we should focus on.

[ProfFan]

It's high time that we have roundtrip tests from header to AST to header 🤣

[varunagrawal]

I potentially came up with a solution to this in #118. Basically, use a dict to keep track of the namespace name and then just add it to the content. I have spent way too much time on multi-file support, so I'll leave this to someone else. 🙂