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EMF Compare and LazyLinkingResource proxy URLs [message #1821511]

Thu, 13 February 2020 19:34

Paul Gaspardo

Messages: 2
Registered: February 2019

Junior Member

I'm working with an Xtext DSL and exploring the possibility of using the EMF Compare RCP UI for model-based Git history diffs to augment the standard text-based diffing.

One behavior I've noticed is that changes in non-containment references are not being detected by EMF Compare. For example, using this State Machine example, if I invert the state transitions to turn

state active
	drawerOpened => waitingForLight
	lightOn		 => waitingForDrawer
end

into

state active
	drawerOpened => waitingForDrawer
	lightOn		 => waitingForLight
end

Then EMF Compare doesn't detect this change.

I believe this is because of the way the proxy URLs used by LazyLinkingResource work - instead of referring to the target EObject they refer to their own position in the source for later decoding, and since that doesn't change they are the same as far as EMF Compare is concerned.

Is there a general way to handle this? I've have some success with a custom IEqualityHelper.

(Note in the example above the reference is within the same file, but in our case we do deal with multiple files)

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Re: EMF Compare and LazyLinkingResource proxy URLs [message #1821699 is a reply to message #1821511]

Tue, 18 February 2020 20:08

Neeraj Bhusare

Messages: 177
Registered: July 2009
Location: Canada

Senior Member

Hi Paul,

From what I remember, EMF Compare detects changes made to the reference (non-containment). Ps testAttributeDatatypeChangedFromClazzTypeToClazzType() - https://bit.ly/2uZQ0jV

All customizations to the EMF Compare framework - https://bit.ly/2P2AR8o

You might like to use the EMF Compare forum for queries specific to EMF Compare - https://bit.ly/2uVzoK5.

I hope this helps.

Twitter : @NeerajBhusare
Blog : https://nbhusare.github.io/
Best regards, Neeraj

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Re: EMF Compare and LazyLinkingResource proxy URLs [message #1821772 is a reply to message #1821699]

Wed, 19 February 2020 22:34

Paul Gaspardo

Messages: 2
Registered: February 2019

Junior Member

Hi Neeraj,

Thanks for the links.

Although I could be misunderstanding, but it looks like in that example EMF Compare on its own is not detecting the non-containment reference change. It's able to do so thanks to the handling of ClassType in the ID computation function passed to the custom IdentityEObjectMatcher (simply accessing type.name is sufficient), but with that removed EMF Compare doesn't detect that ClassType.type was changed without otherwise resolving the proxy references before performing the comparison.

But that does give some ideas to look into, thank you.

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