Hi everyone,

  2 ahab1372 : I tink you're right, sales team should work for that case but unfortunately, my client here wants to use sharing as a condidentiality feature, so it won't be a sharing with the sales team but for exemple with some managers.

 2  mtbclimber :  The way my client uses the oppties pushed me to implement a sync solution. Moreover, the Apex managed sharing is not working for my case either (i had to face the same issue for a custom object), cause when the new owner take the object, he cannot changed the sharing anymore.

So here is what i eventually did, i used a technical field to store the sharing rules in the before update trigger, and to retrieve them in the after update trigger. Then i update the sharing table.

I know it's kind of an ugly solution but i needed to find something quickly!!!

Thank you all for your help and ideas.

Here is a part of the code for those who are interested in :

trigger Opp_Access on Opportunity (before update, after update) {
        // Before the update we collect the sharing rules for the Opp
        if(Trigger.isBefore){
            for (Opportunity Opp : trigger.new){
                // Only if the record owner changed
                if (Trigger.oldMap.get(Opp.id).OwnerId != Opp.OwnerId) {
                    List<OpportunityShare> oppShrList = new List<OpportunityShare>();                    
                    oppShrList=[Select o.UserOrGroupId, o.RowCause, o.OpportunityId, o.OpportunityAccessLevel
                                    From OpportunityShare o Where o.OpportunityId =: Opp.Id];
                                    
                    // The information is stored in a technical field of Opp
                    // Due to its size, the max sharing rules storage is 200 for an Opp
                    Opp.Transfer_Tech__c = ''+oppShrList;
                }
            }
        // After the update, we recreate the rules to keep the same share        
        }else if (Trigger.isAfter){
            for (Opportunity Opp : trigger.new){
                // Only if the record owner changed
                if (Trigger.oldMap.get(Opp.id).OwnerId != Opp.OwnerId) {
                    // Get all the sharing rules in a string
                    String sharingList = Opp.Transfer_Tech__c;
                    // Work on the string to keep only the pertinent info
                    String regex = 'OpportunityShare\\:\\{';
                    String[] sharingListTab = sharingList.split(regex);
                    
                    for(Integer j = 1; j<sharingListTab.size(); j++){
                        // Create the new sharing rules with the stored data
                        OpportunityShare oppShr  = new OpportunityShare();
                        String[] aShareElementsTab = sharingListTab[j].trim().split('\\,');

                        for(Integer k = 0; k<aShareElementsTab.size(); k++){
                            if(aShareElementsTab[k].contains('OpportunityId')){
                                oppShr.OpportunityId = (Id)aShareElementsTab[k].split('\\=')[1].trim();
                            }
                            if(aShareElementsTab[k].contains('UserOrGroupId')){
                                oppShr.UserOrGroupId = (Id)aShareElementsTab[k].split('\\=')[1].trim();
                            }
                            if(aShareElementsTab[k].contains('OpportunityAccessLevel')){
                                String access = aShareElementsTab[k].split('\\=')[1].trim();
                                // If it's the old owner access we only grant him a new read access
                                if(access.equals('All')){
                                    oppShr.OpportunityAccessLevel = 'Read';
                                }else{
                                    oppShr.OpportunityAccessLevel = access;
                                }
                            }
                         }
                        sharesToCreate.add(oppShr);
                    }
                    // Eventually the Oppty has the exact same sharing rules as before transfer
                    Database.SaveResult[] sr = Database.insert(sharesToCreate,false);
                    for(Integer i = 0; i<sr.size(); i++){
                          // Process the save results  
                        if(!sr[i].isSuccess()){
                            // Get save result error  
                            Database.Error err = sr[i].getErrors()[0];
                            if(!(err.getStatusCode() == StatusCode.FIELD_INTEGRITY_EXCEPTION  &&  
                                                err.getMessage().contains('AccessLevel'))){
                                // Throw an error when the error is not related to trivial access level.      
                                trigger.newMap.get(sharesToCreate[i].OpportunityId).
                                  addError('Impossible de garder les règles de partage lors du transfert : '
                                      + err.getMessage());
                            }                        
                        }                        
                     }                    
                }
            }
        }
}