D365FO / Setting default values for custom fields on a vendor invoice from a purchase order (VendInvoiceInfoTable / PurchFormletterParmDataInvoice)

When creating a vendor invoice and you are trying to populate custom fields on table VendInvoiceInfoTable you may find that the following will only work if you are creating a blank invoice and not executing it from the invoice create button on a purchase order

[DataEventHandler(tableStr(VendInvoiceInfoTable), DataEventType::InitializingRecord)] 
 public static void VendInvoiceInfoTable_onInitializingRecord(Common sender, DataEventArgs e) 
 { 
      VendInvoiceInfoTable vendInvoiceInfoTable = sender as VendInvoiceInfoTable; 
      vendInvoiceInfoTable.CustomField   VendParameters::find().DefaultCustomField; 
 }

This is due to the class PurchFormletterParmDataInvoice.createInvoiceHeaderFromTempTable()
which called .skipEvents(true), skipDataMethods(true), .skipDatabaseLog(true) and calls a Query::insert_recordset() because of this none of the default events will get triggered.

In order to properly populate customfields on a blank vendor invoice or creating once from a purchase order the following will need to be done via extensions and CoC.

1. Add custom fields to VendInvoiceInfoTable
2. Add custom fields to VendInvoiceInfoTableTmp (name and types need to match what was created on VendInvoiceInfoTable)
1. We have to add it to this table because on PurchFormLetterParmDataInvoice.insertParmTable() it calls a buf2buf command which loops through the field list.
3. Create extension class of table VendInvoiceInfoTable and apply a CoC of defaultRow method which will populate the value onto both the regular and tmp instance of VendInvoiceInfoTable however it will not save to the database unless the remaining steps are completed
/// <summary>
/// Default values for a vendor invoice header from a purchase order
/// </summary>
[ExtensionOf(tableStr(VendInvoiceInfoTable))]
final class APInvoiceModsVendInvoiceInfoTable_Extension
{
    /// <summary>
    /// COC table method defaultRow which resets default valies
    /// </summary>
    /// <param name = "_purchTable">PurchTable</param>
    /// <param name = "_ledgerJournalTrans">LedgerJournalTrans</param>
    /// <param name = "_resetFieldState">Reset field state</param>
    public void defaultRow(PurchTable _purchTable, LedgerJournalTrans _ledgerJournalTrans, boolean _resetFieldState)
    {
        CustomEDTType defaultCustomField;
        
next defaultRow(_purchTable,_ledgerJournalTrans,_resetFieldState);


        //find the default custom field from vend parms
defaultCustomField = VendParameters::find().DefaultCustomField;
        
//save the default invoice type to the header which will get copied to    VendInvoiceInfoTableTmp and then back to the main table due to PurchFormLetterParmDataInvoice.createInvoiceHeaderFromTempTable
this.CustomField = defaultCustomField;


    }


}
4. Create extension class of PurchFormLletterParmDataInvoice and apply a CoC to buildCreateInvoiceHeaderFromTempTableFieldQuery and buildCreateInvoiceHeaderFromTempTableFieldMap because the method PurchFormletterParmDataInvoice.createInvoiceHeaderFromTempTable() creates a dynamic map of the fields to copy from the temp table into the main table 
[ExtensionOf(classStr(PurchFormletterParmDataInvoice))]
final class APInvoiceModsPurchFormletterParmDataInvoice_Extension
{
    /// <summary>
    /// COC method that adds our custom field to the Field Query selection  from the temp table
    /// </summary>
    /// <param name = "_qbdsVendInvoiceInfoTableTmp">VendInvoiceInfoTableTmp</param>
    protected void buildCreateInvoiceHeaderFromTempTableFieldQuery(QueryBuildDataSource _qbdsVendInvoiceInfoTableTmp)
    {
        next buildCreateInvoiceHeaderFromTempTableFieldQuery(_qbdsVendInvoiceInfoTableTmp);


        //add custom selection field
_qbdsVendInvoiceInfoTableTmp.addSelectionField(fieldNum(VendInvoiceInfoTableTmp, CustomField));
    }


    /// <summary>
    /// COC method thats adds our custom field to the dynamic field map against the main table. Which will get copied from the selection query
    /// </summary>
    /// <param name = "_qbdsVendInvoiceInfoTableTmp">VendInvoiceInfoTableTmp</param>
    /// <returns>Modified dynamic map to insert into the db</returns>
    protected Map buildCreateInvoiceHeaderFromTempTableFieldMap(QueryBuildDataSource _qbdsVendInvoiceInfoTableTmp)
    {
        var targetToSourceMap = next buildCreateInvoiceHeaderFromTempTableFieldMap(_qbdsVendInvoiceInfoTableTmp);
        targetToSourceMap.insert(fieldStr(VendInvoiceInfoTable, CustomField), [_qbdsVendInvoiceInfoTableTmp.uniqueId(), fieldStr(VendInvoiceInfoTableTmp, CustomField)]);
       
return targetToSourceMap;
     }


}

By applying our populate method to the defaultRow() method this will also trigger the value to populated on a blank vendor invoice once a vendor account is selected.