Re: Can I create a package with friendly modules

[Tejas via Digitalmars-d-learn]

On Sunday, 12 June 2022 at 05:05:46 UTC, forkit wrote:
Is it possible to create a package.d, consisting of (for 
example), two modules, where each module can access private 
declarations within each other.

In essence, declaring 'a module level friendship', or a kind of 
'extended module' if you want.

I might still want to add another module to the package, that 
is NOT part of that friendship between those other two modules, 
but is otherwise related to the solution.

You can use `package(qualifiedIdentifier)` to satisfy this to a 
greater extent

Directory structure:
```sh

src
|
|--- main_file.d
|
|---parent
      |
      |--- driver.d
      |
      |--- package.d
      |
      |--- thing
             |
             |--- package.d
             |
             |--- first.d
             |
             |--- second.d
             |
             |--- third.d
```

Code :
`src/main_file.d`:
```d
import parent;

void main()
{
        func();
}
```

`src/parent/package.d`:
```d
module parent;

public import
        driver;
```

`src/parent/driver.d`:
```d
module parent.driver;

import thing;

void func()
{
        S s;                    // from third.d
        auto t = first.a;       // from second.d
        auto l = second.dbl;    // from first.d
}
```

`src/parent/thing/package.d`:
```d
module parent.thing;

public import
        first,
        second,
        third;
```

`src/parent/thing/first.d`:
```d
module thing.first;

import second;

static this()
{
	a = second.g; // can also access symbols within neighbouring 
modules
}
package(parent):
int a;
int b;
string c;
```

`src/parent/thing/second.d`:
```d
module thing.second;

package(parent):

int g;
char p;
double dbl;
```

`src/parent/thing/third.d`:
```d
module thing.third;

package(parent):

struct S
{
        int a;
        char c;
        string s;
}

private S private_struct; // can't access via parent package, 
since marked private
```

You run it via:
`dmd -i -I=./parent -I=./parent/thing main_file.d`
(I'm pretty sure it'll look far prettier using `dub`)

Here, all the symbols that are within package `thing` are visible 
to package `parent` as well, but not visible to any other 
package/module