Create an option for removing overridden rules #7

io.typefox.xtext2langium.tests/src/io/typefox/xtext2langium/tests/Xtext2LangiumMultiLangTest.xtend

@@ -40,6 +40,34 @@ class Xtext2LangiumMultiLangTest extends AbstractXtext2LangiumTest {
 			terminal ID returns string:'^'? ('a' ..'z' | 'A' ..'Z' | '_' )('a' ..'z' | 'A' ..'Z' | '_' | '0' ..'9' )* ;
 			terminal INT returns number:'0' ..'9' +;
 		''')
+		assertGeneratedFile('Terminals.langium', '''
+
+			terminal ID returns string:'^'? ('a' ..'z' | 'A' ..'Z' | '_' )('a' ..'z' | 'A' ..'Z' | '_' | '0' ..'9' )* ;
+			terminal INT returns number:'0' ..'9' +;
+			terminal STRING returns string:'"' ('\\' . |  !('\\' | '"' ))*'"'  | "'" ('\\' . |  !('\\' | "'" ))*"'"  ;
+			hidden terminal ML_COMMENT returns string:'/*'  -> '*/'  ;
+			hidden terminal SL_COMMENT returns string:'//'  !('\n' | '\r' )('\r'? '\n' )?  ;
+			hidden terminal WS returns string:(' ' | '\t' | '\r' | '\n' )+;
+			terminal ANY_OTHER returns string:.;
+		''')
+	}
+	@Test
+	def void testTerminals_02() {
+		'''
+			grammar io.typefox.xtext2langium.Test with org.eclipse.xtext.common.Terminals
+			generate xtext2langiumTest 'http://Xtext2LangiumTest'
+			import "http://www.eclipse.org/emf/2002/Ecore" as ecore
+
+			@Override 
+			terminal ID: '^'?('a'..'z'|'A'..'Z'|'_') ('a'..'z'|'A'..'Z'|'_'|'0'..'9')*;
+			@Override 
+			terminal INT returns ecore::EInt: ('0'..'9')+;
+		'''.assertGeneratedLangium('''
+			import 'Terminals'
+
+			terminal ID returns string:'^'? ('a' ..'z' | 'A' ..'Z' | '_' )('a' ..'z' | 'A' ..'Z' | '_' | '0' ..'9' )* ;
+			terminal INT returns number:'0' ..'9' +;
+		''', [removeOverridenRules = true])
 		assertGeneratedFile('Terminals.langium', '''
 
 			terminal STRING returns string:'"' ('\\' . |  !('\\' | '"' ))*'"'  | "'" ('\\' . |  !('\\' | "'" ))*"'"  ;
@@ -85,7 +113,7 @@ class Xtext2LangiumMultiLangTest extends AbstractXtext2LangiumTest {
 			    greetings+=Greeting * 
 			;
 
-		''')
+		''', [conf | conf.removeOverridenRules = true])
 		assertGeneratedFile('uddl.langium', '''
 			grammar Uddl
 			import 'Terminals'

io.typefox.xtext2langium/src/io/typefox/xtext2langium/Xtext2LangiumFragment.xtend

@@ -71,13 +71,20 @@ class Xtext2LangiumFragment extends AbstractXtextGeneratorFragment {
 	boolean useStringAsEnumRuleType = false
 
 	/**
-	 * If true, types from the ecore metamodel will also be generated.<br>
+	 * If <code>true</code>, types from the ecore metamodel will also be generated.<br>
 	 * If false, ecore data types will be replaced with Langium data types.
 	 * Types that are not convertable to Langium built in types will be generated as string.<br>
-	 * Default is false.<br>
+	 * Default is <code>false</code>.<br>
 	 */
 	@Accessors(PUBLIC_SETTER)
 	boolean generateEcoreTypes = false
+	/**
+	 * In case a rule from the imported grammar was overriden, Langium will report a duplicate error.
+	 * If <code>true</code>, the super grammar rules will be skipped in favor of the current grammar rules.<br>
+	 * Default is <code>false</code>.<br>
+	 */
+	@Accessors(PUBLIC_SETTER)
+	boolean removeOverridenRules = false
 
 	static val INDENT = '    '
 
@@ -117,7 +124,7 @@ class Xtext2LangiumFragment extends AbstractXtextGeneratorFragment {
 		var entryRuleCreated = false
 		for (rule : grammarToGenerate.rules.filter [ rule |
 			/* Filter out rules that were overridden by the sub grammar */
-			subGrammar === null || !subGrammar.rules.exists[name == rule.name]
+			subGrammar === null || !removeOverridenRules || !subGrammar.rules.exists[name == rule.name]
 		]) {
 			if (rule.eClass === PARSER_RULE && !entryRuleCreated) {
 				ctx.out.append('entry ')