shielding #include within namespace { } block?

Question

Edit: I know that method 1 is essentially invalid and will probably use method 2, but I'm looking for the best hack or a better solution to mitigate rampant, mutable namespace proliferation.

I have multiple class or method definitions in one namespace that have different dependencies, and would like to use the fewest namespace blocks or explicit scopings possible but while grouping #include directives with the definitions that require them as best as possible. I've never seen any indication that any preprocessor could be told to exclude namespace {} scoping from #include contents, but I'm here to ask if something similar to this is possible: (see bottom for explanation of why I want something dead simple)

// NOTE: apple.h, etc., contents are *NOT* intended to be in namespace Foo!

// would prefer something most this:
#pragma magic_namespace_backout(1) // FIXME: use actually existing directive
namespace Foo {

#include "apple.h"
B *A::blah(B const *x) { /* ... */ }

#include "banana.h"
int B::whatever(C const &var) { /* ... */ }

#include "blueberry.h"
void B::something() { /* ... */ }

} // namespace Foo

...

// over this:
#include "apple.h"
#include "banana.h"
#include "blueberry.h"

namespace Foo {
B *A::blah(B const *x) { /* ... */ }
int B::whatever(C const &var) { /* ... */ }
void B::something() { /* ... */ }
} // namespace Foo

...

// or over this:
#include "apple.h"
namespace Foo {
B *A::blah(B const *x) { /* ... */ }
} // namespace Foo

#include "banana.h"
namespace Foo {
int B::whatever(C const &var) { /* ... */ }
} // namespace Foo

#include "blueberry.h"
namespace Foo {
void B::something() { /* ... */ }
} // namespace Foo

My real problem is that I have projects where a module may need to be branched but have coexisting components from the branches in the same program. I have classes like FooA, etc., that I've called Foo::A in the hopes being able to branch less painfully as Foo::v1_2::A, where some program may need both a Foo::A and a Foo::v1_2::A. I'd like "Foo" or "Foo::v1_2" to show up only really once per file, as a single namespace block, if possible. Moreover, I tend to prefer to locate blocks of #include directives immediately above the first definition in the file that requires them. What's my best choice, or alternatively, what should I be doing instead of hijacking the namespaces?

Answer 1

Just think of #including as copying and pasting the contents of the included file to the position of the #include directive.

That means, yes, everything in the included file will be inside the namespace.

Answer 2

Q: Can you:
A: Yes you can. The include statement is done during pre-processing before the compiler even sees it.

Q: Is it a good idea.
A: Probably not.

What happens if you #include Apple.g without the namespace tags.
now you have apples declared in the global namespace as-well as the foo namespace.

You should try and avoid situations where you the user of your code needs to understand how it should be used. If your documentation says always #include the apple header file inside the foo namespace that's the bit the user will not read and cause hours of confusion.