From aad95fa6703a6240da630e033e1973c65b9c77f4 Mon Sep 17 00:00:00 2001
From: overflowerror <mail@overflowerror.com>
Date: Thu, 20 Jan 2022 14:00:32 +0100
Subject: [PATCH] fixed problem with repeated empty paths in context

no-progress-in-loop-error is interpreted as nested identity paths - this
is wrong

fix: enable endless loop shortcut in context analysis
---
 .../hoisting/HoistingProcessorTest.java       | 26 ++++++++++++++++---
 .../hoisting/pathAnalysis/TokenAnalysis.java  |  3 ++-
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/org.eclipse.xtext.tests/src/org/eclipse/xtext/xtext/generator/hoisting/HoistingProcessorTest.java b/org.eclipse.xtext.tests/src/org/eclipse/xtext/xtext/generator/hoisting/HoistingProcessorTest.java
index b544165c1..44f2d68c4 100644
--- a/org.eclipse.xtext.tests/src/org/eclipse/xtext/xtext/generator/hoisting/HoistingProcessorTest.java
+++ b/org.eclipse.xtext.tests/src/org/eclipse/xtext/xtext/generator/hoisting/HoistingProcessorTest.java
@@ -1087,8 +1087,6 @@ public class HoistingProcessorTest extends AbstractXtextTests {
 		// @formatter:off
 		String model =
 			MODEL_PREAMBLE +
-			"tokenLimit 4\n" + 
-			"hoistingDebug\n" +
 			"S: a=A ;\n" +
 			"A: $$ p0 $$?=> 'a' \n" +
 			" | $$ p1 $$?=> 'a' s=S ;\n";
@@ -1109,8 +1107,6 @@ public class HoistingProcessorTest extends AbstractXtextTests {
 		// @formatter:off
 		String model =
 			MODEL_PREAMBLE +
-			"tokenLimit 4\n" + 
-			"hoistingDebug\n" +
 			"S: $$ p0 $$?=> 'a' \n" +
 			" | $$ p1 $$?=> 'a' s=S ;\n";
 		// @formatter:off
@@ -1124,4 +1120,26 @@ public class HoistingProcessorTest extends AbstractXtextTests {
 		assertTrue(guard.hasTerminal());
 		assertEquals("((" + getSyntaxForEofToken(2) + " || (p0)) && (" + getSyntaxForKeywordToken("a", 2) + " || (p1)))", guard.render());
 	}
+	
+	@Test
+	public void testRepeatableContextWithEmptyPath_bug_expectCorrectResult() throws Exception {
+		// @formatter:off
+		String model =
+			MODEL_PREAMBLE +
+			"hoistingDebug\n" +
+			"S: A C+ ;\n" +
+			"A: $$ p0 $$?=> 'a' " + 
+			" | $$ p1 $$?=> 'a' 'b' ;\n" +
+			"C: 'c'? ;\n";
+		// @formatter:off
+		XtextResource resource = getResourceFromString(model);
+		Grammar grammar = ((Grammar) resource.getContents().get(0));
+		hoistingProcessor.init(grammar);
+		AbstractRule rule = getRule(grammar, "A");
+		
+		HoistingGuard guard = hoistingProcessor.findHoistingGuard(rule.getAlternatives());
+		assertFalse(guard.isTrivial());
+		assertTrue(guard.hasTerminal());
+		assertEquals("(((" + getSyntaxForEofToken(2) + " && " + getSyntaxForKeywordToken("c", 2) + ") || (p0)) && (" + getSyntaxForKeywordToken("b", 2) + " || (p1)))", guard.render());
+	}
 }
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 0a1f44c75..b4cccbba1 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
@@ -185,7 +185,8 @@ public class TokenAnalysis {
 			log.info("context element: " + abstractElementToShortString(element));
 			TokenAnalysisPaths path = new TokenAnalysisPaths(prefix);
 			path.resetProgress();
-			path = getTokenPaths(element, path, false, false, shortcutEndlessLoops);
+			// shortcut endless loops instead of throwing exception
+			path = getTokenPaths(element, path, false, false, true);
 			if (!path.isDone() && element != null) {
 				if (callStack.contains(element) && !path.hasProgress()) {
 					throw new EmptyRecursionPathInContextAnalysisException("no progress in recursion");