From e5f08c34aa8e1cd8d3e031cee5d0dd1cd9ca5cb7 Mon Sep 17 00:00:00 2001
From: overflowerror <mail@overflowerror.com>
Date: Tue, 11 Jan 2022 22:07:33 +0100
Subject: [PATCH] fixed bug in context analysis

when the following context element is optional, the minimal sequence is
not going to get bigger. in this case further context analysis is
blocked by the exception.
=> removed exception

also made sure getNextElementsInContext() won't return non-token,
non-compound elements like actions or predicates.
---
 .../hoisting/pathAnalysis/TokenAnalysis.java  | 35 +++++++++++++------
 1 file changed, 25 insertions(+), 10 deletions(-)

diff --git a/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/parser/antlr/hoisting/pathAnalysis/TokenAnalysis.java b/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/parser/antlr/hoisting/pathAnalysis/TokenAnalysis.java
index 41953d2da..cc44ee96d 100644
--- a/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/parser/antlr/hoisting/pathAnalysis/TokenAnalysis.java
+++ b/org.eclipse.xtext.xtext.generator/src/org/eclipse/xtext/xtext/generator/parser/antlr/hoisting/pathAnalysis/TokenAnalysis.java
@@ -24,12 +24,15 @@ import org.apache.log4j.Logger;
 import org.eclipse.emf.ecore.EObject;
 import org.eclipse.xtext.AbstractElement;
 import org.eclipse.xtext.AbstractRule;
+import org.eclipse.xtext.AbstractSemanticPredicate;
+import org.eclipse.xtext.Action;
 import org.eclipse.xtext.Alternatives;
 import org.eclipse.xtext.Assignment;
 import org.eclipse.xtext.CompoundElement;
 import org.eclipse.xtext.Grammar;
 import org.eclipse.xtext.GrammarUtil;
 import org.eclipse.xtext.Group;
+import org.eclipse.xtext.JavaAction;
 import org.eclipse.xtext.RuleCall;
 import org.eclipse.xtext.UnorderedGroup;
 import org.eclipse.xtext.util.XtextSwitch;
@@ -82,6 +85,7 @@ public class TokenAnalysis {
 	}
 	
 	private List<AbstractElement> getNextElementsInContext(AbstractElement last) {		
+		// TODO: deal with non-trivial cardinalities
 		CompoundElement container = getCompoundContainer(last);
 		while (container instanceof Alternatives || 
 		       last.eContainer() instanceof Assignment
@@ -112,8 +116,24 @@ public class TokenAnalysis {
 				log.info(last.eClass().getName());
 				log.info(abstractElementToString(container));
 			}
-			if (index < elements.size() - 1) {
-				return Arrays.asList(elements.get(index + 1));
+			
+			int size = elements.size();
+			AbstractElement next = null;
+			
+			while (index < size - 1) {
+				next = elements.get(index + 1);
+				if (!(
+						(next instanceof Action) ||
+						(next instanceof JavaAction) ||
+						(next instanceof AbstractSemanticPredicate)
+				)) {
+					break;
+				}
+					
+				index++;
+			}
+			if (index < size - 1) {
+				return Arrays.asList(next);
 			} else {
 				// this is the last element
 				return getNextElementsInContext(container);
@@ -155,17 +175,12 @@ public class TokenAnalysis {
 			// TODO: is this special case necessary?
 			throw new TokenAnalysisAbortedException("context analysis failed: no context");
 		}
-
-		int currentPosition = prefix.getMinPosition();
 		
-		for (AbstractElement element : context) {			
+		for (AbstractElement element : context) {
+			log.info("context element: " + abstractElementToShortString(element));
 			TokenAnalysisPaths path = new TokenAnalysisPaths(prefix);
 			path = getTokenPaths(element, path, false, false, shortcutEndlessLoops);
-			if (!path.isDone() && element != null) {
-				if (path.getMinPosition() == currentPosition) {
-					throw new TokenAnalysisAbortedException("no progress in context analysis");
-				}
-				
+			if (!path.isDone() && element != null) {				
 				path = getTokenPathsContext(element, path, shortcutEndlessLoops);
 			}
 			if (path.isDone()) {