[news.eclipse.technology.emft] Re: [EMF Compare] 3 way match

[d.aniwltr@xxxxxxxxx ( Daniel)]

Hi Laurent,

I've decided to do the normal 3-way comparison and validate the resulting 
model (don't know how, yet) afterwards.

However I got some problems. The isConflicting() method always returns 
false.
I've changed the same property to different values in File2&3, or changed 
it to a value in one File and deleted it in the other File. Always false.

My other problem is, that I can't get the merge to work.

if I use :    MergeService.merge( differences, true ); i get:

java.util.ConcurrentModificationException
at 
org.eclipse.emf.common.util.BasicEList$EIterator.checkModCount(BasicEList.java:1378)
at 
org.eclipse.emf.common.util.BasicEList$EIterator.doNext(BasicEList.java:1332)
at 
org.eclipse.emf.common.util.BasicEList$EIterator.next(BasicEList.java:1312)
at 
org.eclipse.emf.compare.diff.merge.service.MergeService.merge(MergeService.java:132)


and if i change it to:  MergeService.merge( differences, false ); i get:

java.lang.NullPointerException
at 
org.eclipse.emf.compare.util.EFactory.eStructuralFeature(EFactory.java:216)
at org.eclipse.emf.compare.util.EFactory.eAdd(EFactory.java:58)
at 
org.eclipse.emf.compare.diff.internal.merge.impl.MoveModelElementMerger.applyInOrigin(MoveModelElementMerger.java:44)
at 
org.eclipse.emf.compare.diff.merge.service.MergeService.doMerge(MergeService.java:174)
at 
org.eclipse.emf.compare.diff.merge.service.MergeService.merge(MergeService.java:136)
at 
org.eclipse.emf.compare.diff.internal.merge.impl.DiffGroupMerger.applyInOrigin(DiffGroupMerger.java:35)
at 
org.eclipse.emf.compare.diff.merge.service.MergeService.doMerge(MergeService.java:174)
at 
org.eclipse.emf.compare.diff.merge.service.MergeService.merge(MergeService.java:136)
at 
org.eclipse.emf.compare.diff.internal.merge.impl.DiffGroupMerger.applyInOrigin(DiffGroupMerger.java:35)
at 
org.eclipse.emf.compare.diff.merge.service.MergeService.doMerge(MergeService.java:174)
at 
org.eclipse.emf.compare.diff.merge.service.MergeService.merge(MergeService.java:136)
at 
org.eclipse.emf.compare.diff.internal.merge.impl.DiffGroupMerger.applyInOrigin(DiffGroupMerger.java:35)
at 
org.eclipse.emf.compare.diff.merge.service.MergeService.doMerge(MergeService.java:174)
at 
org.eclipse.emf.compare.diff.merge.service.MergeService.merge(MergeService.java:136)
at 
org.eclipse.emf.compare.diff.internal.merge.impl.DiffGroupMerger.applyInOrigin(DiffGroupMerger.java:35)
at 
org.eclipse.emf.compare.diff.merge.service.MergeService.doMerge(MergeService.java:174)
at 
org.eclipse.emf.compare.diff.merge.service.MergeService.merge(MergeService.java:136)
at 
org.eclipse.emf.compare.diff.internal.merge.impl.DiffGroupMerger.applyInOrigin(DiffGroupMerger.java:35)
at 
org.eclipse.emf.compare.diff.merge.service.MergeService.doMerge(MergeService.java:174)
at 
org.eclipse.emf.compare.diff.merge.service.MergeService.merge(MergeService.java:136)
at 
org.eclipse.emf.compare.diff.internal.merge.impl.DiffGroupMerger.applyInOrigin(DiffGroupMerger.java:35)
at 
org.eclipse.emf.compare.diff.merge.service.MergeService.doMerge(MergeService.java:174)
at 
org.eclipse.emf.compare.diff.merge.service.MergeService.merge(MergeService.java:136)


Do you have any advice or suggestions?

Thanks a lot.

Daniel


laurent Goubet wrote:

> Hi Daniel,

> 3-way matching doesn't seem to be what you seek. As you mentionned, you 
> want to compare File1 with File2, File1 with File3 _and_ File2 with 
> File3... and execute some logic with the results of these comparisons, 
> ignoring part of the changes, resolving conflicts, and merging part of 
> the others. Well the logic here clearly is more important than a 
> standard 3-way diff.

> You might be able to create a mix of changes with 2-way diffing 1 and 2, 
> then 1 and 3 and a 3-way differencing to detect conflicts ... but I 
> think you should clearly determine the needed logic beforehand :p.

> Laurent Goubet
> Obeo

> Daniel a écrit :
> > Hi Laurent,
> >
> > Thanks for your fast answer. I upgraded to 1.0 and finally saw the 
> > methods and classes you were talking about. ;-)
> >
> > The thing with the many movings also dissapeared, seems like a fixed 
> > bug. So I also don't have to do the instance of "ReferenceOrderChange" 
> > check.
> >
> > Still my problem is, that I need to know the origin File of a change, 
> > even if it is not conflicting. This is because the resulting file has to 
> > be conform to the new base, only enhanced with the customizings but 
> > there is logic, which has to be checked before i can add it (even if 
> > nonconflicting)otherwise the model could be unusable.
> >
> > If I check on isRemote() in the 3wayDiff I get a false for every 
> > (nonconflicting) DiffElement in the Diff.
> > So I assume that a 3 way Diff  has only the informations of the ancestor 
> > on one side and a nonconflicting mixture of the changes from the  2 
> > customized childfiles on the other side, however without reference from 
> > which file the changes came from.
> >
> > If it is not possible to get the origin file of a change I have to use 
> > another approach and do two 2way diffs, than somehow compare the diffs 
> > and delete the ones I don't like. Is there some unique id with which i 
> > can compare the DiffElements of two Diffs? (Maybe i'll do a Diff of File 
> > 2 and 3 and then subtract the Diff of File 1 and 3 from it.)
> >
> > Cheers
> >
> > Daniel
> >
> >
> > laurent Goubet wrote:
> >
> > > Hi Daniel,
> >
> > > Comments inlined below.
> >
> > > Daniel a écrit :
> > > > Hi,
> > > > Thank you for your work and effort.
> > > >
> > > > My situation is the following: I have 3 Model instances,
> > > > File 1: a base, File 2: a base file with some customisations
> > > > File 3: and another customized (further developed) base file, say new 
> > > > base.
> > > >
> > > >
> > > > I want to get the customisations of File 2 into file 3. Therefore i 
> > > > have to solve some conflicts between those files.
> > > >
> > > > Firstly I want to make sure that this is the right approach for the 
> > > > 3way match.
> > > > I use the ressourceMatch() Method with the 3 Files, than created a 
> > > > Diff out of it.
> >
> > > conflict detection/resolution can only be made when comparing two 
> > > files along with their common ancestor. Thus you can indeed use 
> > > three-way differencing and hope to have interesting results if both 
> > > your "file3" and "file2" are derived from the same base "file1".
> >
> > > MatchService.doResourceMatch() followed by DiffService.doDiff(match) 
> > > is indeed the way to get the differences.
> >
> > > > 1 Question: How do I ignore changes which only affect the order of 
> > > > the elements? (...has been moved from ... to)
> >
> > > We've never implemented a way to ignore differences when comparing, 
> > > but you can do it programmatically when merging by not merging all 
> > > DiffElements instance of "ReferenceOrderChange".
> >
> > > > 2 Question: I get an Diff out of the 3way Matchmodel, but how do i 
> > > > get the origin file of a DiffElement? So how do I know if the change 
> > > > was between file 1 and 2 or 1 and 3?
> >
> > > MatchService.doResourceMatch takes 3 resources as parameter : left, 
> > > right and ancestor (in this order). Talking in terms of version 
> > > control system, "left" is your "local" resource (File3), "right" is 
> > > the remote file (on repository) (File2) and "ancestor" is, well, the 
> > > common ancestor of both files (File1).
> >
> > > With 3-way changes, we'll see "remote" changes and "normal" changes. 
> > > Namely, if you have a Class "Class1" in File1, File2 has renamed this 
> > > class "Class2" and File3 sports a change in which the class is renamed 
> > > "Class3", we'll detect a conflicting change. In the DiffModel, this 
> > > means we'll have a "ConflictingDiffElement" containing an 
> > > "AttributeChange" for the change to "Class3" and a remote 
> > > "AttributeChange" (which method "isRemote() returns true) for the 
> > > change to "Class2".
> >
> > > In opposition, if your File2 had changed the name of your class to 
> > > "Class" and File3 has done the same, no difference would have even 
> > > been detected even though File1 had this class named "Class1".
> >
> > > You can know whether the change had been made in File2 if it is marked 
> > > as a "remote" change.
> >
> > > > 3 Question: I've found a graphic with a "diff extensions" api marked. 
> > > > But where and how do I use this api, and can I use it to manually 
> > > > solve the conflicts with it?
> >
> > > The diff extension API can be used to change the DiffModel itself by 
> > > regrouping differencesin order to "hide" them between a higher 
> > > difference. This doesn't seem to be what you seek.
> >
> > > If you want to merge differences, use the MergeService API (similar to 
> > > MatchService and DiffService, this allows you to merge differences 
> > > easily given the DiffModel). Conflict resolution is only a matter of 
> > > merging the conflicting difference from left to right or right to left 
> > > (in my exemple above, File3 to File2 or File2 to File3 respectively).
> >
> > > We might need to implement a "smarter" conflict resolution API, but 
> > > for now that's what you can access :).
> >
> > > > Thank you in advance,
> > > > greetings
> > > >
> > > > Daniel
> >
> > > Cheers,
> >
> > > Laurent Goubet
> > > Obeo