From 5284ac7228155087117806ca31147b33dba2a397 Mon Sep 17 00:00:00 2001
From: Tpt <thomaspt@hotmail.fr>
Date: Fri, 21 Oct 2022 14:47:30 +0200
Subject: [PATCH] Variable should stay not bound in subqueries even if they are
 bound in the parent query

Closes #261
---
 lib/src/sparql/eval.rs                        | 43 +++++++++++--------
 testsuite/oxigraph-tests/sparql/manifest.ttl  |  7 +++
 .../sparql/unbound_variable_in_subquery.rq    |  6 +++
 .../sparql/unbound_variable_in_subquery.srx   | 17 ++++++++
 4 files changed, 56 insertions(+), 17 deletions(-)
 create mode 100644 testsuite/oxigraph-tests/sparql/unbound_variable_in_subquery.rq
 create mode 100644 testsuite/oxigraph-tests/sparql/unbound_variable_in_subquery.srx

diff --git a/lib/src/sparql/eval.rs b/lib/src/sparql/eval.rs
index 4f2d031c..87a803a5 100644
--- a/lib/src/sparql/eval.rs
+++ b/lib/src/sparql/eval.rs
@@ -531,23 +531,32 @@ impl SimpleEvaluator {
                 let mapping = mapping.clone();
                 Rc::new(move |from| {
                     let mapping = mapping.clone();
-                    // We map forward the "from" values to make sure we join wit them
-                    let mut inner_from = EncodedTuple::with_capacity(mapping.len());
-                    for (input_key, output_key) in mapping.iter() {
-                        if let Some(value) = from.get(*output_key) {
-                            inner_from.set(*input_key, value.clone());
-                        }
-                    }
-                    Box::new(child(inner_from).map(move |tuple| {
-                        let tuple = tuple?;
-                        let mut output_tuple = from.clone();
-                        for (input_key, output_key) in mapping.iter() {
-                            if let Some(value) = tuple.get(*input_key) {
-                                output_tuple.set(*output_key, value.clone());
-                            }
-                        }
-                        Ok(output_tuple)
-                    }))
+                    Box::new(
+                        child(EncodedTuple::with_capacity(mapping.len())).filter_map(
+                            move |tuple| {
+                                match tuple {
+                                    Ok(tuple) => {
+                                        let mut output_tuple = from.clone();
+                                        for (input_key, output_key) in mapping.iter() {
+                                            if let Some(value) = tuple.get(*input_key) {
+                                                if let Some(existing_value) =
+                                                    output_tuple.get(*output_key)
+                                                {
+                                                    if existing_value != value {
+                                                        return None; // Conflict
+                                                    }
+                                                } else {
+                                                    output_tuple.set(*output_key, value.clone());
+                                                }
+                                            }
+                                        }
+                                        Some(Ok(output_tuple))
+                                    }
+                                    Err(e) => Some(Err(e)),
+                                }
+                            },
+                        ),
+                    )
                 })
             }
             PlanNode::Aggregate {
diff --git a/testsuite/oxigraph-tests/sparql/manifest.ttl b/testsuite/oxigraph-tests/sparql/manifest.ttl
index e215c315..621c63e9 100644
--- a/testsuite/oxigraph-tests/sparql/manifest.ttl
+++ b/testsuite/oxigraph-tests/sparql/manifest.ttl
@@ -27,6 +27,7 @@
     :nested_expression
     :order_terms
     :nested_anonymous
+    :unbound_variable_in_subquery
     ) .
 
 :small_unicode_escape_with_multibytes_char rdf:type mf:NegativeSyntaxTest ;
@@ -122,3 +123,9 @@
          [ qt:query  <nested_anonymous.rq> ;
            qt:data   <nested_anonymous.ttl> ] ;
     mf:result  <nested_anonymous.srx> .
+
+:unbound_variable_in_subquery rdf:type mf:QueryEvaluationTest ;
+    mf:name "Variable should stay not bound in subqueries even if they are bound in the parent query" ;
+    mf:action
+         [ qt:query  <unbound_variable_in_subquery.rq> ] ;
+    mf:result  <unbound_variable_in_subquery.srx> .
diff --git a/testsuite/oxigraph-tests/sparql/unbound_variable_in_subquery.rq b/testsuite/oxigraph-tests/sparql/unbound_variable_in_subquery.rq
new file mode 100644
index 00000000..3669a898
--- /dev/null
+++ b/testsuite/oxigraph-tests/sparql/unbound_variable_in_subquery.rq
@@ -0,0 +1,6 @@
+PREFIX ex: <http://example.com/>
+
+SELECT ?a ?b WHERE {
+    BIND(ex:a as ?a)
+    {SELECT ?b WHERE { BIND(ex:b as ?b) FILTER(!BOUND(?a))}}
+}
diff --git a/testsuite/oxigraph-tests/sparql/unbound_variable_in_subquery.srx b/testsuite/oxigraph-tests/sparql/unbound_variable_in_subquery.srx
new file mode 100644
index 00000000..3ee6cb7d
--- /dev/null
+++ b/testsuite/oxigraph-tests/sparql/unbound_variable_in_subquery.srx
@@ -0,0 +1,17 @@
+<?xml version="1.0"?>
+<sparql xmlns="http://www.w3.org/2005/sparql-results#">
+    <head>
+        <variable name="a"/>
+        <variable name="b"/>
+    </head>
+    <results>
+        <result>
+            <binding name="a">
+                <uri>http://example.com/a</uri>
+            </binding>
+            <binding name="b">
+                <uri>http://example.com/b</uri>
+            </binding>
+        </result>
+    </results>
+</sparql>
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