Strange behavior with library import resolution (with in GPR files)

[Heziode]

I encountered a strange behavior while resolving an issue with a library. I have provided an example program below for reference:

with Ada.Command_Line; use Ada.Command_Line;
with Ada.Environment_Variables;
with Ada.Text_IO;
with Ada.Exceptions;

with GPR2.Project.View;
with GPR2.Project.Tree;
with GPR2.Project.Attribute.Set;
with GPR2.Context;
with GPR2.Message;
with GPR2.Log;

procedure Main is

   use Ada;
   use GPR2;
   use GPR2.Project;

   procedure Display (Prj : Project.View.Object);

   procedure Display (Att : Project.Attribute.Object);

   -------------
   -- Display --
   -------------

   procedure Display (Att : Project.Attribute.Object) is
   begin
      Text_IO.Put ("   " & String (Image (Att.Name.Id.Attr)));
      if Att.Has_Index then
         Text_IO.Put (" (" & Att.Index.Value & ")");
      end if;

      Text_IO.Put (" -> ");

      for V of Att.Values loop
         Text_IO.Put (V.Text & " ");
      end loop;
      Text_IO.New_Line;
   end Display;

   procedure Display (Prj : Project.View.Object) is
      use GPR2.Project.Attribute.Set;

      Is_First : Boolean := True;
   begin
      if Prj.Has_Imports then
         for W of Prj.Imports loop
            Ada.Text_IO.Put_Line (String (W.Path_Name.Name));
         end loop;
      end if;
      Text_IO.Put_Line (Prj.Kind'Img);

   end Display;

   Prj : Project.Tree.Object;
   Ctx : Context.Object;

   procedure Print_Messages is
   begin
      if Prj.Has_Messages then
         for C in Prj.Log_Messages.Iterate (False, True, True, True, True) loop
            Ada.Text_IO.Put_Line (GPR2.Log.Element (C).Format);
         end loop;
      end if;
   end Print_Messages;

begin
   -- Check if an argument is provided
   if Argument_Count = 0 then
      -- No argument provided
      Ada.Text_IO.Put_Line ("You need to specify the GPR file to process!");
      return;
   end if;

   Text_IO.Put_Line (Ada.Environment_Variables.Value ("GPR_PROJECT_PATH"));

   declare
      Arg : Filename_Type := Filename_Type (Argument (1));
   begin
      Project.Tree.Load
        (Self => Prj, Filename => Create (Arg), Context => Ctx);
   end;

   Display (Prj.Root_Project);

exception
   when Ex : others =>
      Text_IO.Put_Line (Ada.Exceptions.Exception_Message (Ex));
      Print_Messages;
      raise;
end Main;

The program produces a gpr2withlist bin file. To reproduce the issue, follow the steps below:

1. Run the command alr get -b lace_opengl to obtain the Lace_OpenGL project and build it using Alire.
2. Navigate to the lace_opengl_0.1.0_672a6415/library directory.
3. Execute the command gpr2withlist opengl.gpr.

The following error occurs:

/tmp/lace_opengl_0.1.0_672a6415/library/opengl.gpr: fatal error, cannot load the project tree
gl.gpr:2:06: error: imported project file "lace_shared.gpr" not found

raised GPR2.PROJECT_ERROR : /tmp/lace_opengl_0.1.0_672a6415/library/opengl.gpr: fatal error, cannot load the project tree
[/workspaces/bench-source/gpr_to_source_dirs/bin/gpr_with_extract]
0x564f753a0304 gpr2__project__tree__load__2 at ???
0x564f753a06d8 gpr2__project__tree__load at ???
0x564f7507552c Main at gpr_with_extract.adb:109
0x564f75078fd3 Main at b__gpr_with_extract.adb:2384
[/lib/x86_64-linux-gnu/libc.so.6]
0x7f3870df0188
0x7f3870df0243
[/workspaces/bench-source/gpr_to_source_dirs/bin/gpr_with_extract]
0x564f750746af _start at ???
0xfffffffffffffffe

As you can see, the error states that the imported project file "lace_shared.gpr" is not found, which is an "expected" behavior, since none of the project and these dependencies are in resolution path (e.g. GPR_PROJECT_PATH).

However, when I perform the following steps, the error changes:

1. Navigate to the /tmp/lace_opengl_0.1.0_672a6415 directory.
2. Run the command eval `alr printenv` to retrieve the source environment from Alire.
3. Navigate to the sub-directory library
4. Execute the command gpr2withlist opengl.gpr.

The new error is as follows:

/tmp/lace_opengl_0.1.0_672a6415/alire/cache/dependencies/lace_collada_0.1.0_99d5bbb7/library:/tmp/lace_opengl_0.1.0_672a6415/alire/cache/dependencies/lace_math_0.1.0_3ab67197/library:/tmp/lace_opengl_0.1.0_672a6415/alire/cache/dependencies/lace_shared_0.1.0_bc8f1534:/tmp/lace_opengl_0.1.0_672a6415/alire/cache/dependencies/lace_xml_0.1.0_b6aa904a/library:/tmp/lace_opengl_0.1.0_672a6415/library:.:/tmp/Comps:/tmp/Asiscomps:
/tmp/lace_opengl_0.1.0_672a6415/library/opengl.gpr semantic error
opengl_core.gpr:34:20: error: undefined project "Lace_shared"

raised GPR2.PROJECT_ERROR : /tmp/lace_opengl_0.1

.0_672a6415/library/opengl.gpr semantic error
[/workspaces/bench-source/gpr_to_source_dirs/bin/gpr_with_extract]
0x55ce0f42bec8 gpr2__project__tree__set_context__2 at ???
0x55ce0f42c497 gpr2__project__tree__set_context at ???
0x55ce0f42e407 gpr2__project__tree__load__2 at ???
0x55ce0f42f6d8 gpr2__project__tree__load at ???
0x55ce0f10452c Main at gpr_with_extract.adb:109
0x55ce0f107fd3 Main at b__gpr_with_extract.adb:2384
[/lib/x86_64-linux-gnu/libc.so.6]
0x7f8c78d91188
0x7f8c78d91243
[/workspaces/bench-source/gpr_to_source_dirs/bin/gpr_with_extract]
0x55ce0f1036af _start at ???
0xfffffffffffffffe

Now, the error message states that the project "Lace_shared" is undefined, even though lace_shared.gpr can be resolved.

To work around this issue, it is necessary to edit all .gpr files and move the abstract project to the first imported project.