[xtend][grammar] Allow modifiers and visibility keywords to appear in any order - test fixes and value converters

https://bugs.eclipse.org/bugs/show_bug.cgi?id=381327

Change-Id: I26a6a57c5704fabcbe66d0282beed4e5896a232d

plugins/org.eclipse.xtext/src/org/eclipse/xtext/conversion/impl/NonRecursiveKeywordAlternativeConverter.java

@@ -0,0 +1,101 @@
+/*******************************************************************************
+ * Copyright (c) 2011 itemis AG (http://www.itemis.eu) and others.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *******************************************************************************/
+package org.eclipse.xtext.conversion.impl;
+
+import java.util.Set;
+
+import org.eclipse.xtext.AbstractElement;
+import org.eclipse.xtext.AbstractRule;
+import org.eclipse.xtext.Alternatives;
+import org.eclipse.xtext.GrammarUtil;
+import org.eclipse.xtext.Keyword;
+import org.eclipse.xtext.RuleCall;
+import org.eclipse.xtext.TerminalRule;
+import org.eclipse.xtext.conversion.IValueConverter;
+import org.eclipse.xtext.conversion.IValueConverterService;
+import org.eclipse.xtext.conversion.ValueConverterException;
+import org.eclipse.xtext.nodemodel.INode;
+
+import com.google.common.collect.ImmutableSet;
+import com.google.inject.Inject;
+
+/**
+ * @author Jan Koehnlein - Initial contribution and API
+ * @since 2.4
+ */
+public class NonRecursiveKeywordAlternativeConverter extends AbstractValueConverter<String> implements IValueConverter.RuleSpecific {
+
+	private Set<String> keywords;
+	
+	private AbstractRule terminalRule;
+	
+	@Inject
+	private IValueConverterService delegateService;
+
+	private AbstractRule rule;
+
+	public String toValue(String string, INode node) throws ValueConverterException {
+		if (keywords.contains(string))
+			return string;
+		String result = (String) delegateService.toValue(string, terminalRule.getName(), node);
+		return result;
+	}
+
+	public String toString(String value) throws ValueConverterException {
+		if (keywords.contains(value))
+			return value;
+		String result = delegateService.toString(value, terminalRule.getName());
+		return result;
+	}
+
+	protected String keywordToString(Keyword keyword) {
+		return keyword.getValue();
+	}
+
+	/**
+	 * @throws IllegalArgumentException if the rule is not a datatype rule or does not fulfill
+	 *   the pattern <pre>RuleName: 'keyword' | 'other';</pre>
+	 */
+	public void setRule(AbstractRule rule) {
+		this.rule = rule;
+		ImmutableSet.Builder<String> builder = ImmutableSet.builder();
+		handleRule(rule, builder);
+		keywords = builder.build();
+		if(terminalRule == null)
+			throw new IllegalArgumentException("Could not find terminal rule in call graph of " + rule.getName());
+	}
+
+	protected void handleRule(AbstractRule rule, ImmutableSet.Builder<String> builder) {
+		if(rule instanceof TerminalRule) {
+			if(terminalRule != null) 
+				throw new IllegalArgumentException("Terminal rule is already set in " + this.rule.getName());
+			terminalRule = rule;
+			return;			
+		}
+		if (!GrammarUtil.isDatatypeRule(rule))
+			throw new IllegalArgumentException(rule.getName() + " is not a data type rule");
+		if (!(rule.getAlternatives() instanceof Alternatives)) {
+			if (rule.getAlternatives() instanceof RuleCall) {
+				handleRule(((RuleCall) rule.getAlternatives()).getRule(), builder);
+			}
+			throw new IllegalArgumentException(rule.getName() + " is not an alternative and not a rule call");
+		}
+		Alternatives alternatives = (Alternatives) rule.getAlternatives();
+		for(AbstractElement element: alternatives.getElements()) {
+			if (element instanceof Keyword) {
+				builder.add(keywordToString((Keyword) element));
+			} else if (element instanceof RuleCall) {
+				AbstractRule calledRule = ((RuleCall) element).getRule();
+				handleRule(calledRule, builder);
+			} else {
+				throw new IllegalArgumentException(rule.getName() + "'s body does not contain an alternative of keywords and a single rule");
+			}
+		}
+	} 
+	
+}