Fix Other_File for separates of subprograms without spec

Fix Other_File for the case when it is called on a separate,
whose body stub is defined in a library subprogram body
that does not have a separate spec.
Improve its comment to clarify situation with separates.
Add test.

Change-Id: I55afa476b646370cda0a106a21d62cde66c12217
TN: U805-042

Author: fedor-rybin

src/gnatcoll-projects.adb

@@ -2887,7 +2887,29 @@ package body GNATCOLL.Projects is
                if Unit (J) = '.' then
                   declare
                      Base : constant Filesystem_String := File_From_Unit
-                       (Project (Info), Unit (Unit'First .. J - 1), Part,
+                       (Project (Info), Unit (Unit'First .. J - 1), Unit_Spec,
+                        Language => Info.Language);
+                  begin
+                     if Base'Length > 0 then
+                        return Self.Create (Base, Use_Object_Path => False);
+                     end if;
+                  end;
+               end if;
+            end loop;
+         end if;
+
+         --  Second special case for separate units. When no parent spec has
+         --  been found, there still exists a scenario when separate is from
+         --  a body unit that does not have a spec. We need an extra loop
+         --  to not wrongly pick up the case when there is a chain of separates
+         --  one declared in another.
+
+         if Info.Part = Unit_Separate then
+            for J in reverse Unit'Range loop
+               if Unit (J) = '.' then
+                  declare
+                     Base : constant Filesystem_String := File_From_Unit
+                       (Project (Info), Unit (Unit'First .. J - 1), Unit_Body,
                         Language => Info.Language);
                   begin
                      if Base'Length > 0 then

src/gnatcoll-projects.ads

@@ -669,8 +669,12 @@ package GNATCOLL.Projects is
    function Other_File
      (Self : Project_Tree;
       File : GNATCOLL.VFS.Virtual_File) return GNATCOLL.VFS.Virtual_File;
-   --  If Info is a spec, returns the body of the same unit. If Info is a
+   --  If File is a spec, returns the body of the same unit. If File is a
    --  body, returns its spec.
+   --  If File is a separate, returns parent (possibly indirect, looping
+   --  through the chain of separates) unit spec. In case when a body stub
+   --  is defined in a library subprogram body that does not have a separate
+   --  spec, returns subprogram body file.
    --  If there is no "other file" in the project, but we could compute the
    --  name it should have, that name is returned (the file is created in the
    --  same directory as File).

testsuite/tests/projects/separate_of_subprogram/main-separate_of_body.adb

@@ -0,0 +1,5 @@
+separate (Main)
+procedure Separate_Of_Body is
+begin
+   null;
+end Separate_Of_Body;

testsuite/tests/projects/separate_of_subprogram/main.adb

@@ -0,0 +1,7 @@
+with Pkg_0;
+procedure Main is
+   procedure Separate_Of_Body is separate;
+begin
+   null;
+end Main;
+

testsuite/tests/projects/separate_of_subprogram/pkg_0-p_separate_common.adb

@@ -0,0 +1,5 @@
+separate (Pkg_0)
+procedure P_Separate_Common is
+begin
+   null;
+end P_Separate_Common;

testsuite/tests/projects/separate_of_subprogram/pkg_0-pack-p_separate_of_separate.adb

@@ -0,0 +1,5 @@
+separate (Pkg_0.Pack)
+procedure P_Separate_Of_Separate is
+begin
+   null;
+end P_Separate_Of_Separate;

testsuite/tests/projects/separate_of_subprogram/pkg_0-pack.adb

@@ -0,0 +1,4 @@
+separate (Pkg_0)
+package body Pack is
+   procedure P_Separate_Of_Separate is separate;
+end Pack;

testsuite/tests/projects/separate_of_subprogram/pkg_0.adb

@@ -0,0 +1,5 @@
+package body Pkg_0 is
+   procedure P_Separate_Common is separate;
+
+   package body Pack is separate;
+end Pkg_0;

testsuite/tests/projects/separate_of_subprogram/pkg_0.ads

@@ -0,0 +1,6 @@
+package Pkg_0 is
+   procedure P_Separate_Common;
+   package Pack is
+      procedure P_Separate_Of_Separate;
+   end Pack;
+end Pkg_0;

testsuite/tests/projects/separate_of_subprogram/prj.gpr

@@ -0,0 +1,4 @@
+project Prj is
+   for Main use ("main.adb");
+end Prj;
+