Xtext problem referencing grammar A from validator of grammar B

In Xtext, how do I follow a reference from grammar B to grammar A, within a validator of grammar B (which is in the ui-plugin)? Consider the following example.

Grammar A is org.xtext.people.People

org.xtext.people.People

grammar org.xtext.people.People with org.eclipse.xtext.common.Terminals

generate people "http://www.xtext.org/people/People"

People:
people+=Person*;

Person:
'person' name=ID ';';


and an instance

person Alice citizenship "MN"; id "12345";
person Bob citizenship "CH"; id "54321";
person Malice citizenship "XXX"; id "66666";


At an airport, entries of people are recorded.

enter Alice;
enter Bob;
enter Malice;


Entries are modelled with a second grammar B org.xtext.entries.Entries

org.xtext.entries.Entries

grammar org.xtext.entries.Entries with org.eclipse.xtext.common.Terminals

generate entries "http://www.xtext.org/entries/Entries"
import "http://www.xtext.org/people/People"

Entries:
entries+=Entry*;

Entry:
'enter' person=[Person] ';';


After ensuring that the Eclipse project org.xtext.entries has the project org.xtext.people on it's classpath, and ensuring that the org.xtext.entries plugin has the org.xtext.people as a dependency, all works as expected.

org.xtext.entries

org.xtext.people

org.xtext.entries

org.xtext.people

There is a travel ban on people from country XXX, although certain deserving people are excluded. Only the CIA knows who is excluded from the ban. Entries must not be allowed for people from XXX unless excluded.

The updated grammar is

grammar org.xtext.entries.Entries with org.eclipse.xtext.common.Terminals

generate entries "http://www.xtext.org/entries/Entries"


import "http://www.xtext.org/people/People"

Entries:
entries+=Entry*;

Entry:
travelBanOverride=TravelBanOverride?
'enter' person=[Person] ';';

TravelBanOverride: '@TravelBanOverride' '(' code=STRING ')';


with validator

package org.xtext.entries.validation

import org.eclipse.xtext.validation.Check
import org.xtext.entries.entries.EntriesPackage
import org.xtext.entries.entries.Entry
import org.xtext.entries.CIA

class EntriesValidator extends AbstractEntriesValidator

public static val BAN = 'BAN'
public static val ILLEGAL_OVERRIDE = 'ILLEGAL_OVERRIDE'

@Check
def checkBan(Entry entry)
if (entry.person.citizenship == "XXX")
if (entry.travelBanOverride === null)
error('Violation of Travel Ban', EntriesPackage.Literals.ENTRY__PERSON, BAN)

else
val overridecode = entry.travelBanOverride.code;
val valid = CIA.valid(entry.person.name, entry.person.id, overridecode)
if (!valid)
error('Illegal override code', EntriesPackage.Literals.ENTRY__TRAVEL_BAN_OVERRIDE, ILLEGAL_OVERRIDE)










where the driver for the external CIA web-app is modelled for example by

package org.xtext.entries;

public class CIA


public static boolean valid(String name, String id, String overrideCode)
System.out.println("UNValid["+name+","+overrideCode+"]");
return name.equals("Malice") && id.equals("66666") && overrideCode.equals("123");





The validations work as expected.

I now wish to provided a quick-fix for BAN, that checks for an override code from the CIA.

BAN

package org.xtext.entries.ui.quickfix

import org.eclipse.xtext.ui.editor.quickfix.DefaultQuickfixProvider
import org.eclipse.xtext.ui.editor.quickfix.Fix
import org.xtext.entries.validation.EntriesValidator
import org.eclipse.xtext.validation.Issue
import org.eclipse.xtext.ui.editor.quickfix.IssueResolutionAcceptor
import org.xtext.entries.entries.Entry
import org.xtext.entries.Helper

class EntriesQuickfixProvider extends DefaultQuickfixProvider

@Fix(EntriesValidator.BAN)
def tryOverride(Issue issue, IssueResolutionAcceptor acceptor)
val entry = element as Entry
// val person = entry.person // no such attribute
//val person = Helper.get(entry); // The method get(Entry) from the type Helper refers to the missing type Object
]




The first commented line does not compile: there is no attribute person. The second commented line is an attempt to solve the problem by getting a helper class in org.xtext.entries to get the person, but this does not compile either, giving a "The method get(Entry) from the type Helper refers to the missing type Object" error message.

person

org.xtext.entries

For completeness, here is that helper.

package org.xtext.entries

import org.xtext.people.people.Person
import org.xtext.entries.entries.Entry

class Helper

static def Person get(Entry entry)
return entry.person;





Further, entry.travelBanOverride compiles fine, but entry.person does not. Clicking on Entry in Eclipse takes one to the expected code, which has both travelBanOverride and person.

entry.travelBanOverride

entry.person

travelBanOverride

person

The issue does not occur with a Java class in the same project and package.

package org.xtext.entries.ui.quickfix;

import org.xtext.entries.entries.Entry;
import org.xtext.people.people.Person;

public class Test

public static void main(String args)
Entry entry = null;
Person p = entry.getPerson();




Rewriting the quickfix in Java solves the problem.

package org.xtext.entries.ui.quickfix;

import org.eclipse.xtext.ui.editor.quickfix.DefaultQuickfixProvider;
import org.eclipse.xtext.ui.editor.quickfix.Fix;
import org.xtext.entries.validation.EntriesValidator;
import org.eclipse.xtext.validation.Issue;
import org.eclipse.xtext.ui.editor.quickfix.IssueResolutionAcceptor;
import org.xtext.entries.entries.Entry;
import org.xtext.entries.Helper;
import org.eclipse.xtext.ui.editor.model.edit.IModificationContext;
import org.eclipse.xtext.ui.editor.model.edit.ISemanticModification;
import org.eclipse.emf.ecore.EObject;
import org.xtext.entries.entries.Entry;
import org.xtext.people.people.Person;

public class EntriesQuickfixProvider extends DefaultQuickfixProvider



@Fix(EntriesValidator.BAN)
public void tryOverride(final Issue issue, IssueResolutionAcceptor acceptor)
acceptor.accept(issue,
"Try to override",
"Override",
"override.gif",
new ISemanticModification()
public void apply(EObject element, IModificationContext context)
Entry entry = (Entry) element;
System.out.println(entry.getPerson());


);





entry.travelBanOverride

entry.person

travelBanOverride

person

1 Answer
1

My mistake is the following.

After ensuring that the Eclipse project org.xtext.entries has the
project org.xtext.people on it's classpath, and ensuring that the
org.xtext.entries plugin has the org.xtext.people as a dependency, all
works as expected.

The org.xtext.entries.ui ui-plugin must also have the org.xtext.people on its Java (Eclipse project) build path. Exporting and making a plugin-dependency it not enough.

org.xtext.entries.ui

org.xtext.people

Note that this setting should be made early, before crafting the quick-fix, because the Xtend editor has refreshing issues.

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