Serialization of parsed model leads to invalid code

[lukasf98]

Given the following grammar:

grammar org.eclipse.xtext.example.fowlerdsl.Statemachine with org.eclipse.xtext.common.Terminals

generate statemachine "http://www.eclipse.org/xtext/example/fowlerdsl/Statemachine"

Statemachine :
	{Statemachine}
	(('events' ('{'
		events+=Event*
	'}'))? &
	('resetEvents' ('{'
		resetEvents+=[Event]*
	'}'))? &
	('commands' ('{'
		commands+=Command*
	'}'))? &
	states+=State* )
;

Event:
	name=ID code=ID
;

Command:
	name=ID code=ID
;

State:
	'state' name=ID
		('actions' '{' actions+=[Command]+ '}')?
		transitions+=Transition*
	'end'
;

Transition:
	event=[Event] '=>' state=[State]
;

If i parse and the serialize tho following code:

resetEvents {
	doorOpened
}

events {
	doorClosed		D1CL
	drawerOpened	D2OP
	lightOn			L1ON
	doorOpened		D1OP
	panelClosed		PNCL
}

commands {
	unlockPanel PNUL
	lockPanel	NLK
	lockDoor	D1LK
	unlockDoor	D1UL
}

state idle
	actions {unlockDoor lockPanel}
	doorClosed => active
end

state active
	drawerOpened => waitingForLight
	lightOn		 => waitingForDrawer
end

state waitingForLight
	lightOn => unlockedPanel
end

state waitingForDrawer
	drawerOpened => unlockedPanel
end

state unlockedPanel
	actions {unlockPanel lockDoor}
	panelClosed => idle
end

The serialization of the parsed model leads to invalid code:

resetEvents
	{
	doorOpened
}

resetEvents {
}

events
	{
	doorClosed   D1CL
	drawerOpened D2OP
	lightOn      L1ON
	doorOpened   D1OP
	panelClosed  PNCL
}

events {
}

commands
	{
	unlockPanel PNUL
	lockPanel   NLK
	lockDoor    D1LK
	unlockDoor  D1UL
}

state idle
	actions {unlockDoor lockPanel}
	doorClosed => active
end

state active
	drawerOpened => waitingForLight
	lightOn      => waitingForDrawer
end

state waitingForLight
	lightOn => unlockedPanel
end

state waitingForDrawer
	drawerOpened => unlockedPanel
end

state unlockedPanel
	actions {unlockPanel lockDoor}
	panelClosed => idle
end

Ass seen above the first to statements are duplicated with an empty statement.
Attached below is an example project to reproduce the issue.
See teste org.eclipse.xtext.example.fowlerdsl.tests.StatemachineParsingTest
IssueDuplicate.zip

[cdietrich]

eclipse-xtext/xtext#2580
might be related.
throwing away the nodemodel seems to help here too

[lukasf98]

eclipse-xtext/xtext#2580 might be related. throwing away the nodemodel seems to help here too

Thanks a lot for your reply. I tested it and it solves the problem I described above. However I ran into an issue with a comma seperated list. If I for example change the grammar for resetEvents to a comma seperated list:

('resetEvents' ('{'
	(resetEvents+=[Event] (',' resetEvents+=[Event])*)?
'}'))? &

And I execute the test org.eclipse.xtext.example.fowlerdsl.tests.StatemachineParsingTest (see attachement) I get two resetEvents Statements:

resetEvents { 
	doorOpened 
} 
resetEvents { 
	doorClosed 
}

IssueDuplicate2.zip

[cdietrich]

If metamodel does not matter can you move each clause to extra rule

[lukasf98]

If metamodel does not matter can you move each clause to extra rule

What do you mean exactly? Extracting (resetEvents+=[Event] (',' resetEvents+=[Event])*)? into a seperate rule?

[cdietrich]

yes

[lukasf98]

Thanks a lot. I tested it with the example I provided and changed the grammar:

Statemachine :
	{Statemachine}
	(('events' ('{'
		events+=Event*
	'}'))? &
	('resetEvents' ('{'
		resetEvents=ResetEvents
	'}'))? &
	('commands' ('{'
		commands+=Command*
	'}'))? &
	states+=State* )
;

ResetEvents:
	{ResetEvents} (resetEvents+=[Event] (',' resetEvents+=[Event])*)?;

While that works, I can't change the metamodel in my real project. Therfore we decided to make the comma optional and move to lists without commas in the future. In my example that means changing the grammar to the following:

('resetEvents' ('{'
	(resetEvents+=[Event] ','?)*
'}'))? &

[lukasf98]

@cdietrich

I have one problem left:
If I throw away the nodemodel and then serialize my code I loose my comments.
Do you have an idea how I can retain them?

[cdietrich]

no, none besides make them explicit

[szarnekow]

I don't see something here that's different from eclipse-xtext/xtext#2580. Closing