This Blog Talks about handling custom errors when creating/changing SAP Purchase orders both at header level and item level. It also tries to explain error handling using the standard Macros mmpur_context and  mmcnt_context_badi.

Header Level Error Handling using Method PROCESS_HEADER of the BADI

Make sure you add the include which holds Macors for message handling ( as shown below)

One example we can look at is, raise error message when a service PO Validity date entered by user should no be less that current date.

INCLUDE mm_messages_mac. "useful macros for message handling

*Get Header details

DATA: lwa_hdr TYPE mepoheader.

*   Get Document Type
lwa_hdr = im_header->get_data( ).

( Below is example where we want raise error when validity period is less than current date)

IF lwa_hdr-kdatb < sy-datlo.

*STEP 1 --> Invalidate Header object

*         invalidate the object
CALL METHOD im_header->invalidate( ).

*Add a custom Error Context ( the number is important to remove messages when required)
mmpur_context 910. 
mmpur_message_forced 'E' 'ZXYZ' '007' lv_msgv1 '' '' ''. 

     ELSE.

*In Case of No error, call the macro to remove message
mmpur_remove_msg_by_context lwa_hdr-id 910.
ENDIF.

Item Level Error Handling using Method PROCESS_ITEM of the BADI

Example –> Raise Error Message at item level to make sure that only item category K or 2 ( Consignment) is allowed if the material entered has the field SOBSL (Special Procurement Type) is set to 10 ( Consignment) .

DATA: lwa_item  TYPE mepoitem

* im_item of PROCESS_ITEM can be used as a referance to get item data
lwa_item = im_item->get_data( ).

IF lwa_item-matnr IS NOT INITIAL.

lv_msgv1 = lwa_item-ebelp.

mmpur_context 921.   " New Context 921 to be added

mmpur_business_obj_id lwa_item-id. " To ensure right item gets flagged for error

mmpur_message_forced 'E' 'ZXYZ' '005' lv_msgv1 '' '' ''. 

*         invalidate the object
CALL METHOD lr_item->invalidate( ).  " Invlidate Ite,

ELSE.
mmpur_remove_msg_by_context lwa_item-id 921 . " Needed if Message is to be removed                                          "upon user correction

ENDIF

Importance of METHOD CHECK in BADI

In Some instances we have seen that the Methods PROCESS_HEADER & PROCESS_ITEM are not called , for example when creating Purchase Order with reference to Contract or when creating Purchase Order by copying existing PO. ( This is the behavior that we noticed, so any suggestions or comments are welcome)  . In such instances we need to add validation in Method CHECK, as this method gets called during CHECK & SAVE Events of PO.

The Key thing in CHECK PO is to make sure we set the flag CH_FAILED to ‘X’ when custom validation fails

IF " Custom Validation Failed

lv_msgv1 = lwa_item-ebelp.

mmpur_context 921.
mmpur_business_obj_id lwa_item-id.
mmpur_message_forced 'E' 'ZXYZ' '005' lv_msgv1 '' '' ''. 

*         invalidate the object
CALL METHOD lr_item->invalidate( ).

ch_failed = abap_true.

ELSE.
mmpur_remove_msg_by_context lwa_item-id 921 .

ENDIF.

Importance of BADI ME_HOLD_PO 

Even after adding custom error messages as mentioned earlier, SAP allows the PO to be saved in status HOLD. If there is a requirement to make sure that a PO does not get saved until all the errors are corrected, we can use BADI “ME_HOLD_PO”. All you need to do is create implementation and set the flag CH_ALLOWED = SPACE.