Convert nested ABAP structure into Flat structure

nested2flat_structure.abap

DATA: lo_structure_descriptor type ref to cl_abap_structdescr,
      lo_structure_descriptor_tmp type ref to cl_abap_structdescr,
      lo_table_descriptor type ref to cl_abap_tabledescr,
      lt_structure_components_nested   type cl_abap_structdescr=>component_table,
      lt_structure_components_flat type cl_abap_structdescr=>component_table,
      lv_index type sy-tabix.
      
lo_table_descriptor ?= cl_abap_structdescr=>describe_by_data( lt_result_table_nested ).
lo_structure_descriptor ?= lo_table_descriptor->get_table_line_type(  ).
lt_structure_components = lo_structure_descriptor->get_components( ).

loop at lt_structure_components_nested ASSIGNING FIELD-SYMBOL(<fs_component>).
  lv_index = sy-tabix.
  IF <fs_component>-type->kind EQ 'E'.
*   Add only elemantary components to component table 
    APPEND <fs_component> to lt_structure_components_flat.
  ENDIF.
  IF <fs_component>-type->kind EQ 'S'.
*     Expand nested structures before adding their elements to component table 
      lo_structure_descriptor_tmp ?= <fs_component>-type.
      data(nested_components) = lo_structure_descriptor_tmp->get_components( ).
      loop at nested_components ASSIGNING FIELD-SYMBOL(<fs_nested_component>).
          if line_exists( lt_structure_components_nested[ name = <fs_nested_component>-name ] ).
*             Workaround for duplicate file-names
              <fs_nested_component>-name = <fs_comp>-name && `_` && <fs_new_comp>-name.
          ENDIF.
*         Insert after current index (preserves sort order) 
          INSERT <fs_nested_component> INTO lt_structure_components_nested INDEX ( lv_index + sy-tabix ).
      ENDLOOP.
  ENDIF.
ENDLOOP.

* Prepare the output table 
DATA: lo_output_structdescr type ref to cl_abap_structdescr,
      lo_output_tabledescr type ref to cl_abap_tabledescr,
      lo_output_struc  type ref to data,
      lo_output_ttype  type ref to data.


field-symbols: <fs_table> type standard table,
               <fs_line>  type any.

* create structure and table type descriptor
lo_output_structdescr = cl_abap_structdescr=>create( lt_structure_components_flat ).
lo_output_tabledescr = cl_abap_tabledescr=>create(
  p_line_type  = cl_abap_structdescr=>create( lt_structure_components_flat )
  p_table_kind = cl_abap_tabledescr=>tablekind_std
  p_unique     = abap_false
).

* handle runtime data type by means of generic variables
create data: lo_output_struc type handle lo_output_structdescr,
             lo_output_ttype type handle lo_output_tabledescr.

assign: lo_output_struc->* to <fs_line>,
        lo_output_ttype->* to <fs_table>.

* Move data to flat strucutre from nested structure
loop at lt_result_table_nested ASSIGNING FIELD-SYMBOL(<fs_result>).
  MOVE-CORRESPONDING <fs_result> to <fs_line>.
  MOVE-CORRESPONDING <fs_result>-nested-structure to <fs_line>. 
* Note: Incomplete solution, as renamed (duplicate components occuring in multiple nested structures) can't be moved this way.  
  APPEND <fs_line> to <fs_table>.
ENDLOOP.