From 74529be4f7da2ce1a16c5542df073a1911859751 Mon Sep 17 00:00:00 2001
From: Jeremy Coulon <jeremy.coulon@3ds.com>
Date: Tue, 10 Apr 2018 17:19:29 +0200
Subject: [PATCH 1/2] Add UT showing the problem

---
 .../sparql/algebra/TestTransformOpExt.java    | 31 +++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/jena-arq/src/test/java/org/apache/jena/sparql/algebra/TestTransformOpExt.java b/jena-arq/src/test/java/org/apache/jena/sparql/algebra/TestTransformOpExt.java
index 0e5bc1dbeab..12bb2f12f22 100644
--- a/jena-arq/src/test/java/org/apache/jena/sparql/algebra/TestTransformOpExt.java
+++ b/jena-arq/src/test/java/org/apache/jena/sparql/algebra/TestTransformOpExt.java
@@ -18,11 +18,15 @@
 
 package org.apache.jena.sparql.algebra;
 
+import java.util.Set;
+
 import org.apache.jena.atlas.io.IndentedWriter ;
 import org.apache.jena.atlas.junit.BaseTest ;
 import org.apache.jena.atlas.lib.StrUtils ;
 import org.apache.jena.sparql.algebra.op.OpExt ;
+import org.apache.jena.sparql.algebra.op.OpFilter;
 import org.apache.jena.sparql.algebra.op.OpGraph ;
+import org.apache.jena.sparql.core.Var;
 import org.apache.jena.sparql.engine.ExecutionContext ;
 import org.apache.jena.sparql.engine.QueryIterator ;
 import org.apache.jena.sparql.serializer.SerializationContext ;
@@ -69,6 +73,14 @@ public boolean equalTo(Op other, NodeIsomorphismMap labelMap) {
         }
     }
     
+    static class OpExtTransform extends TransformCopy {
+        
+        @Override
+        public Op transform(OpFilter opFilter, Op subOp) {
+            return new OpExtTest(opFilter);
+        }
+    }
+    
     @Test public void textOpExtQuads() {
         String x = StrUtils.strjoinNL
             ("(graph <g>"
@@ -100,5 +112,24 @@ public boolean equalTo(Op other, NodeIsomorphismMap labelMap) {
         Op expectedSub = SSE.parseOp(y) ;
         assertEquals(expectedSub, opSub) ;
     }
+    
+    @Test
+    public void testOpExtMinus() {
+        String sse = StrUtils.strjoinNL
+                ("(filter (= ?o 1)"
+                ,"   (bgp (?s ?p ?o))"
+                ,")"
+                ) ;
+        
+        // Build 
+        Op op = SSE.parseOp(sse) ;
+        
+        // Transform
+        op = Transformer.transformSkipService(new OpExtTransform(), op) ;
+        
+        // Check WalkerVisitorVisible
+        Set<Var> vars = OpVars.visibleVars(op);
+        assertEquals(3, vars.size());
+    }
 }
 

From 9c2bb1c183a70fafa1007857823e91aca9a1f18f Mon Sep 17 00:00:00 2001
From: Jeremy Coulon <jeremy.coulon@3ds.com>
Date: Tue, 10 Apr 2018 17:20:08 +0200
Subject: [PATCH 2/2] Fix OpWalkerVisitor for OpExt

---
 .../src/main/java/org/apache/jena/sparql/algebra/OpVars.java | 5 +++++
 .../main/java/org/apache/jena/sparql/algebra/OpWalker.java   | 1 +
 2 files changed, 6 insertions(+)

diff --git a/jena-arq/src/main/java/org/apache/jena/sparql/algebra/OpVars.java b/jena-arq/src/main/java/org/apache/jena/sparql/algebra/OpVars.java
index 70f649e4ec1..9cfec1c9a9b 100644
--- a/jena-arq/src/main/java/org/apache/jena/sparql/algebra/OpVars.java
+++ b/jena-arq/src/main/java/org/apache/jena/sparql/algebra/OpVars.java
@@ -284,6 +284,11 @@ public void visit(OpPropFunc opPropFunc) {
         public void visit(OpProcedure opProc) {
             ExprVars.varsMentioned(acc, opProc.getArgs()) ;
         }
+        
+        @Override
+        public void visit(OpExt opExt) {
+            // OpWalkerVisitor is taking care of calling opExt.effectiveOp().visit(this)
+        }
     }
     
     private static class OpVarsPatternWithPositions extends OpVisitorBase
diff --git a/jena-arq/src/main/java/org/apache/jena/sparql/algebra/OpWalker.java b/jena-arq/src/main/java/org/apache/jena/sparql/algebra/OpWalker.java
index 378e0aed67a..55bf4e75329 100644
--- a/jena-arq/src/main/java/org/apache/jena/sparql/algebra/OpWalker.java
+++ b/jena-arq/src/main/java/org/apache/jena/sparql/algebra/OpWalker.java
@@ -139,6 +139,7 @@ protected void visitN(OpN op) {
         @Override
         protected void visitExt(OpExt op) {
             before(op) ;
+            super.visitExt(op);
             if ( visitor != null )
                 op.visit(visitor) ;
             after(op) ;