feat(model): Model change listener

[tdurieux]

Close #1168

[monperrus]

remove?

[tdurieux]

I need it for CtJavaDocImpl

[monperrus]

rename spoon.diff in spoon.experimental.modelobs
put ChangeFactory in spoon.experimental.modelobs
add spoon.experimental.package-info.java:

this is unstable code, subject to potential complete redesign, not only in snapshots but also in releases. you can use this code but you'll probably be impacted upon future changes. 

move addArgument to separate PR

[monperrus]

split ChangeFactory into ChangeFactory (empty on*) and ListeningChangeFactory

[tdurieux]

Done for me.

@pvojtechovsky Do you see something to improve?

[pvojtechovsky]

Nice code! I would not do it better. It is OK for me. Sometime I would prefer more comments ;-)

I like that it is by default disabled and that it adds no overhead if it is not needed.
I like Contexts and Actions and fast and low level FineModelChangeListener and higher level ActionBasedChangeListener.

Here are some topics for further discussion:

• Why FineModelChangeListener is not an interface?
• The CtExecutable#setParameters(List<CtParameter<?>> parameters) calls listener deleteAll and then add ... I can imagine some use cases where firing event about remove and add on the same element might be a problem (the element (e.g. parameter) will be marked dirty even if it was not really touched). What about another FineModelChangeListener method onListSet, which might internally call deleteAll and add, but implementor have a chance to detect what elements were really removed/added by listening on onListSet. Or we might use new UpdateMultipleAction, where value would be a kind of Collection.
• All the collections returned by any model getter should be readonly in future. So clients are forced to use appropriate modification methods.

The topics above might be discussed/solved later - after this big PR is merged.

Anyway thank You for this effort!

[monperrus]

We're almost done :-)

• remove addArgument in interface/impl
• undo change in return type of removeType, removeArgument

[spoon-bot]

Revapi Analysis results

Old API: fr.inria.gforge.spoon:spoon-core:jar:5.8.0-20170627.123204-68

New API: fr.inria.gforge.spoon:spoon-core:jar:5.8.0-SNAPSHOT

Detected changes: 2.

Change 1

Name	Element
Old	none
New	method spoon.experimental.modelobs.FineModelChangeListener spoon.compiler.Environment::getModelChangeListener()
Code	java.method.addedToInterface
Description	Method was added to an interface.
Breaking	binary: non_breaking

Change 2

Name	Element
Old	none
New	method void spoon.compiler.Environment::setModelChangeListener(spoon.experimental.modelobs.FineModelChangeListener)
Code	java.method.addedToInterface
Description	Method was added to an interface.
Breaking	binary: non_breaking

[tdurieux]

Done for me

[monperrus]

Thanks @GerardPaligot for the intial work on this. Kudos @tdurieux for the heavyweight rebase and design improvements.

[pvojtechovsky]

Thanks @everybody for that great feature!