Implement nested id support

Now the 'id' specifier can optionally include the data member path
to the id inside the composite value. For example:

#pragma db id(first)
std::pair<int, int> p;

Note that one somewhat counter-intuitive aspect of this new feature
is that the whole member marked with id ('p' in the above example)
and not just the actual id member ('p.first' in the above example)
is treated as readonly.

Such nested id also cannot be automatically assigned (auto specifier).

1 files changed, 12 insertions, 4 deletions

diff --git a/odb/processor.cxx b/odb/processor.cxx
index f7a2be2..5dc49f9 100644
--- a/odb/processor.cxx
+++ b/odb/processor.cxx
@@ -46,7 +46,7 @@ namespace
   id_tree_type (semantics::names*& hint)
   {
     context& c (context::current ());
-    semantics::data_member& id (*context::id_member (*c.top_object));
+    data_member_path& id (*context::id_member (*c.top_object));
     return &c.utype (id, hint);
   }
 
@@ -2109,7 +2109,10 @@ namespace
     virtual void
     traverse_object_pre (type& c)
     {
-      semantics::class_* poly_root (polymorphic (c));
+      using semantics::class_;
+      using semantics::data_member;
+
+      class_* poly_root (polymorphic (c));
 
       // Sections.
       //
@@ -2199,7 +2202,8 @@ namespace
         using namespace semantics;
         using semantics::data_member;
 
-        data_member* idm (id_member (*poly_root));
+        data_member_path& id (*id_member (*poly_root));
+        data_member* idm (id.front ());
 
         if (poly_root != &c)
         {
@@ -2248,8 +2252,12 @@ namespace
 
           // Mark it as a special kind of id.
           //
-          m.set ("id", true);
+          m.set ("id", string ());
           m.set ("polymorphic-ref", true);
+
+          // Make sure we also use the same column name as the root.
+          //
+          m.set ("column", table_column (column_name (id)));
         }
         else
         {