List classes at compile time

[evilrat]

On Saturday, 19 October 2024 at 08:51:20 UTC, Noé Falzon wrote:
> tl;dr: is it possible to iterate over all classes in a program 
> at compile time (or possibly all derived classes from a given 
> base class) to use in a mixin?
>

No, parent class can not possibly know who extends it, just think 
about dynamic libraries...

And unfortunately there is no single place to know every possible 
module used in a build for various reasons, the closest thing you 
can do is obtain modules present in a separate compilation unit, 
i.e. a module with its imports.

as seen with 'dummy' module parent, you cannot get above it.

in this case dummy module is here, but if for example I also had 
another module I can't access it this way without importing it 
some way or another.

```d
import std.stdio;
import std.algorithm;
import dummy;

enum foo = "we need foo just to get something accessible in this 
module";

pragma(msg, __traits(allMembers, __traits(parent, foo)));  // 
prints AliasSeq!("object", "std", "dummy", "foo")

//pragma(msg, __traits(allMembers, __traits(parent, dummy))); // 
Error: argument `dummy` has no parent
```

>
> The closest I got so far is to generate the list of names with 
> a pre-build command that greps through the sources for relevant 
> class names, and a file import:
>

The only improvement to this I can think of is to use D AST 
parser that reliably understands code structure.

The example of this you can find in godot-d class finder, other 
than that it works exactly same.

https://github.com/godot-dlang/godot-dlang/blob/534024c7e27522d6120a9b64e8ef183b79416539/modules/tools/classfinder/godot/tools/classfinder/package.d


Just in case, there is a possible way to get modules at RUNTIME, 
and from there ModuleInfo has list of classes and other type 
information.

https://dlang.org/phobos/object.html#.ModuleInfo.localClasses

```d
import std.stdio;

void main() {
     // ModuleInfo without parenthesis will call opDelegate to 
acquire list of modules known at runtime
     foreach(m; ModuleInfo) {
         writeln(m.name);
     }
}
```

prints

   rt.lifetime
   rt.dmain2
   core.internal.gc.proxy
   rt.deh_win64_posix
   core.exception
   ...