Support BASE declarations in SPARQL queries (#1786)

So far, the `BASE` keyword was supported for `Turtle` inputs, but not as part of a `SPARQL` query. Now it is correctly supported in all cases

src/engine/sparqlExpressions/NaryExpression.h

@@ -65,7 +65,8 @@ SparqlExpression::Ptr makeStrLangTagExpression(SparqlExpression::Ptr child1,
                                                SparqlExpression::Ptr child2);
 
 SparqlExpression::Ptr makeStrExpression(SparqlExpression::Ptr child);
-SparqlExpression::Ptr makeIriOrUriExpression(SparqlExpression::Ptr child);
+SparqlExpression::Ptr makeIriOrUriExpression(SparqlExpression::Ptr child,
+                                             SparqlExpression::Ptr baseIri);
 SparqlExpression::Ptr makeStrlenExpression(SparqlExpression::Ptr child);
 SparqlExpression::Ptr makeSubstrExpression(SparqlExpression::Ptr string,
                                            SparqlExpression::Ptr start,

src/engine/sparqlExpressions/StringExpressions.cpp

@@ -117,14 +117,36 @@ struct LiftStringFunction {
 
 // IRI or URI
 //
-// 1. Check for `BASE` URL and if it exists, prepend it.
-// 2. What's the correct behavior for non-strings, like `1` or `true`?
+// 1. What's the correct behavior for non-strings, like `1` or `true`?
 //
-// @1: TODO implement `BASE`
-// @2: Only a `LiteralOrIri` or an `Id` from `Vocab`/`LocalVocab` is in
+// @1: Only a `LiteralOrIri` or an `Id` from `Vocab`/`LocalVocab` is in
 // consideration within the `IriOrUriValueGetter`, hence automatically
 // ignores values like `1`, `true`, `Date` etc.
-using IriOrUriExpression = NARY<1, FV<std::identity, IriOrUriValueGetter>>;
+
+const Iri& extractIri(const IdOrLiteralOrIri& litOrIri) {
+  AD_CORRECTNESS_CHECK(std::holds_alternative<LocalVocabEntry>(litOrIri));
+  const auto& baseIriOrUri = std::get<LocalVocabEntry>(litOrIri);
+  AD_CORRECTNESS_CHECK(baseIriOrUri.isIri());
+  return baseIriOrUri.getIri();
+}
+
+[[maybe_unused]] auto applyBaseIfPresent =
+    [](IdOrLiteralOrIri iri, const IdOrLiteralOrIri& base) -> IdOrLiteralOrIri {
+  if (std::holds_alternative<Id>(iri)) {
+    AD_CORRECTNESS_CHECK(std::get<Id>(iri).isUndefined());
+    return iri;
+  }
+  const auto& baseIri = extractIri(base);
+  if (baseIri.empty()) {
+    return iri;
+  }
+  // TODO<RobinTF> Avoid unnecessary string copies because of conversion.
+  return LiteralOrIri{Iri::fromIrirefConsiderBase(
+      extractIri(iri).toStringRepresentation(), baseIri.getBaseIri(false),
+      baseIri.getBaseIri(true))};
+};
+using IriOrUriExpression =
+    NARY<2, FV<decltype(applyBaseIfPresent), IriOrUriValueGetter>>;
 
 // STRLEN
 [[maybe_unused]] auto strlen = [](std::string_view s) {
@@ -554,8 +576,8 @@ CPP_template(typename T,
 }
 Expr makeStrExpression(Expr child) { return make<StrExpression>(child); }
 
-Expr makeIriOrUriExpression(Expr child) {
-  return make<IriOrUriExpression>(child);
+Expr makeIriOrUriExpression(Expr child, SparqlExpression::Ptr baseIri) {
+  return make<IriOrUriExpression>(child, baseIri);
 }
 
 Expr makeStrlenExpression(Expr child) { return make<StrlenExpression>(child); }

src/parser/sparqlParser/SparqlQleverVisitor.cpp

@@ -1162,8 +1162,16 @@ TripleComponent::Iri Visitor::visit(Parser::IriContext* ctx) {
 }
 
 // ____________________________________________________________________________________
-string Visitor::visit(Parser::IrirefContext* ctx) {
-  return RdfEscaping::unescapeIriref(ctx->getText());
+string Visitor::visit(Parser::IrirefContext* ctx) const {
+  if (baseIri_.empty()) {
+    return ctx->getText();
+  }
+  // TODO<RobinTF> Avoid unnecessary string copies because of conversion.
+  // Handle IRIs with base IRI.
+  return std::move(
+      ad_utility::triple_component::Iri::fromIrirefConsiderBase(
+          ctx->getText(), baseIri_.getBaseIri(false), baseIri_.getBaseIri(true))
+          .toStringRepresentation());
 }
 
 // ____________________________________________________________________________________
@@ -1211,8 +1219,17 @@ DatasetClause SparqlQleverVisitor::visit(Parser::UsingClauseContext* ctx) {
 
 // ____________________________________________________________________________________
 void Visitor::visit(Parser::PrologueContext* ctx) {
-  visitVector(ctx->baseDecl());
-  visitVector(ctx->prefixDecl());
+  // Process in an interleaved way, so PREFIX statements are processed correctly
+  // to only use the BASE IRIs defined before them, not after them.
+  for (auto* child : ctx->children) {
+    if (auto* baseDecl = dynamic_cast<Parser::BaseDeclContext*>(child)) {
+      visit(baseDecl);
+    } else {
+      auto* prefixDecl = dynamic_cast<Parser::PrefixDeclContext*>(child);
+      AD_CORRECTNESS_CHECK(prefixDecl != nullptr);
+      visit(prefixDecl);
+    }
+  }
   // Remember the whole prologue (we need this when we encounter a SERVICE
   // clause, see `visit(ServiceGraphPatternContext*)` below.
   if (ctx->getStart() && ctx->getStop()) {
@@ -1221,8 +1238,15 @@ void Visitor::visit(Parser::PrologueContext* ctx) {
 }
 
 // ____________________________________________________________________________________
-void Visitor::visit(const Parser::BaseDeclContext* ctx) {
-  reportNotSupported(ctx, "BASE declarations are");
+void Visitor::visit(Parser::BaseDeclContext* ctx) {
+  auto rawIri = ctx->iriref()->getText();
+  bool hasScheme = ctre::starts_with<"<[A-Za-z]*[A-Za-z0-9+-.]:">(rawIri);
+  if (!hasScheme) {
+    reportError(
+        ctx,
+        "The base IRI must be an absolute IRI with a scheme, was: " + rawIri);
+  }
+  baseIri_ = TripleComponent::Iri::fromIriref(visit(ctx->iriref()));
 }
 
 // ____________________________________________________________________________________
@@ -2330,7 +2354,9 @@ ExpressionPtr Visitor::visit([[maybe_unused]] Parser::BuiltInCallContext* ctx) {
   if (functionName == "str") {
     return createUnary(&makeStrExpression);
   } else if (functionName == "iri" || functionName == "uri") {
-    return createUnary(&makeIriOrUriExpression);
+    AD_CORRECTNESS_CHECK(argList.size() == 1, argList.size());
+    return makeIriOrUriExpression(std::move(argList[0]),
+                                  std::make_unique<IriExpression>(baseIri_));
   } else if (functionName == "strlang") {
     return createBinary(&makeStrLangTagExpression);
   } else if (functionName == "strdt") {

src/parser/sparqlParser/SparqlQleverVisitor.h

@@ -80,6 +80,7 @@ class SparqlQleverVisitor {
   // `addVisibleVariable`.
   std::vector<Variable> visibleVariables_{};
   PrefixMap prefixMap_{};
+  ad_utility::triple_component::Iri baseIri_{};
   // We need to remember the prologue (prefix declarations) when we encounter it
   // because we need it when we encounter a SERVICE query. When there is no
   // prologue, this string simply remains empty.
@@ -122,7 +123,7 @@ class SparqlQleverVisitor {
   void visit(Parser::PrologueContext* ctx);
 
   // ___________________________________________________________________________
-  [[noreturn]] static void visit(const Parser::BaseDeclContext* ctx);
+  void visit(Parser::BaseDeclContext* ctx);
 
   // ___________________________________________________________________________
   void visit(Parser::PrefixDeclContext* ctx);
@@ -469,7 +470,7 @@ class SparqlQleverVisitor {
 
   TripleComponent::Iri visit(Parser::IriContext* ctx);
 
-  static string visit(Parser::IrirefContext* ctx);
+  string visit(Parser::IrirefContext* ctx) const;
 
   string visit(Parser::PrefixedNameContext* ctx);
 

test/SparqlAntlrParserTest.cpp

@@ -1587,8 +1587,16 @@ TEST(SparqlParser, builtInCall) {
   expectBuiltInCall("ucaSe(?x)", matchUnary(&makeUppercaseExpression));
   expectBuiltInCall("lCase(?x)", matchUnary(&makeLowercaseExpression));
   expectBuiltInCall("StR(?x)", matchUnary(&makeStrExpression));
-  expectBuiltInCall("iRI(?x)", matchUnary(&makeIriOrUriExpression));
-  expectBuiltInCall("uRI(?x)", matchUnary(&makeIriOrUriExpression));
+  expectBuiltInCall(
+      "iRI(?x)",
+      matchNaryWithChildrenMatchers(
+          &makeIriOrUriExpression, variableExpressionMatcher(Variable{"?x"}),
+          matchLiteralExpression(ad_utility::triple_component::Iri{})));
+  expectBuiltInCall(
+      "uRI(?x)",
+      matchNaryWithChildrenMatchers(
+          &makeIriOrUriExpression, variableExpressionMatcher(Variable{"?x"}),
+          matchLiteralExpression(ad_utility::triple_component::Iri{})));
   expectBuiltInCall("year(?x)", matchUnary(&makeYearExpression));
   expectBuiltInCall("month(?x)", matchUnary(&makeMonthExpression));
   expectBuiltInCall("tz(?x)", matchUnary(&makeTimezoneStrExpression));

test/SparqlExpressionTest.cpp

@@ -573,13 +573,15 @@ TEST(SparqlExpression, dateOperators) {
 }
 
 // _____________________________________________________________________________________
+namespace {
 auto checkStrlen = testUnaryExpression<&makeStrlenExpression>;
 auto checkStr = testUnaryExpression<&makeStrExpression>;
-auto checkIriOrUri = testUnaryExpression<&makeIriOrUriExpression>;
-static auto makeStrlenWithStr = [](auto arg) {
+auto checkIriOrUri = testNaryExpressionVec<&makeIriOrUriExpression>;
+auto makeStrlenWithStr = [](auto arg) {
   return makeStrlenExpression(makeStrExpression(std::move(arg)));
 };
 auto checkStrlenWithStrChild = testUnaryExpression<makeStrlenWithStr>;
+}  // namespace
 TEST(SparqlExpression, stringOperators) {
   // Test `StrlenExpression` and `StrExpression`.
   checkStrlen(
@@ -614,20 +616,13 @@ TEST(SparqlExpression, stringOperators) {
       DateYearOrDuration(11853, DateYearOrDuration::Type::Year));
   // Test `iriOrUriExpression`.
   // test invalid
-  checkIriOrUri(IdOrLiteralOrIriVec{U, IntId(2), DoubleId(12.99), dateDate,
-                                    dateLYear, T, F},
-                IdOrLiteralOrIriVec{U, U, U, U, U, U, U});
+  checkIriOrUri(IdOrLiteralOrIriVec{U, U, U, U, U, U, U},
+                std::tuple{IdOrLiteralOrIriVec{U, IntId(2), DoubleId(12.99),
+                                               dateDate, dateLYear, T, F},
+                           IdOrLiteralOrIri{LocalVocabEntry{
+                               ad_utility::triple_component::Iri{}}}});
   // test valid
   checkIriOrUri(
-      IdOrLiteralOrIriVec{
-          lit("bimbim"), iriref("<bambim>"),
-          lit("https://www.bimbimbam/2001/bamString"),
-          lit("http://www.w3.\torg/2001/\nXMLSchema#\runsignedShort"),
-          lit("http://www.w3.org/2001/XMLSchema#string"),
-          iriref("<http://www.w3.org/2001/XMLSchema#string>"),
-          testContext().notInVocabIri, testContext().notInVocabIriLit,
-          lit("http://example/"), iriref("<http://\t\t\nexample/>"),
-          lit("\t\n\r")},
       IdOrLiteralOrIriVec{
           iriref("<bimbim>"), iriref("<bambim>"),
           iriref("<https://www.bimbimbam/2001/bamString>"),
@@ -637,7 +632,35 @@ TEST(SparqlExpression, stringOperators) {
           iriref("<http://www.w3.org/1999/02/22-rdf-syntax-ns#langString>"),
           iriref("<http://www.w3.org/1999/02/22-rdf-syntax-ns#langString>"),
           iriref("<http://example/>"), iriref("<http://\t\t\nexample/>"),
-          iriref("<\t\n\r>")});
+          iriref("<\t\n\r>")},
+      std::tuple{
+          IdOrLiteralOrIriVec{
+              lit("bimbim"), iriref("<bambim>"),
+              lit("https://www.bimbimbam/2001/bamString"),
+              lit("http://www.w3.\torg/2001/\nXMLSchema#\runsignedShort"),
+              lit("http://www.w3.org/2001/XMLSchema#string"),
+              iriref("<http://www.w3.org/2001/XMLSchema#string>"),
+              testContext().notInVocabIri, testContext().notInVocabIriLit,
+              lit("http://example/"), iriref("<http://\t\t\nexample/>"),
+              lit("\t\n\r")},
+          IdOrLiteralOrIri{
+              LocalVocabEntry{ad_utility::triple_component::Iri{}}}});
+
+  // test with base iri
+  checkIriOrUri(
+      IdOrLiteralOrIriVec{
+          U,
+          iriref("<http://example.com/hi/bimbim>"),
+          iriref("<http://example.com/hi/bambim>"),
+          iriref("<https://www.bimbimbam/2001/bamString>"),
+          iriref("<http://example.com/hello>"),
+          iriref("<http://example.com/hello>"),
+      },
+      std::tuple{
+          IdOrLiteralOrIriVec{U, lit("bimbim"), iriref("<bambim>"),
+                              lit("https://www.bimbimbam/2001/bamString"),
+                              lit("/hello"), iriref("</hello>")},
+          IdOrLiteralOrIri{iriref("<http://example.com/hi>")}});
 
   // A simple test for uniqueness of the cache key.
   auto c1a = makeStrlenExpression(std::make_unique<IriExpression>(iri("<bim>")))

test/SparqlParserTest.cpp

@@ -1349,3 +1349,38 @@ TEST(ParserTest, HandlesSurrogatesCorrectly) {
   // So writing unit tests for these cases is not possible without creating
   // semi-invalid UTF-8 strings.
 }
+
+// _____________________________________________________________________________
+TEST(ParserTest, BaseDeclaration) {
+  // Simple case
+  auto query1 = SparqlParser::parseQuery(
+      "BASE <http://example.org/> SELECT * WHERE { ?s <p> <test> }");
+  EXPECT_EQ(getFirstTriple(query1),
+            "{s: ?s, p: <http://example.org/p>, o: <http://example.org/test>}");
+  // Relative and absolute IRIs mixed
+  auto query2 = SparqlParser::parseQuery(
+      "BASE <http://example.org/something> "
+      "SELECT * WHERE { </root> <p> <http://other.example.org/p> }");
+  EXPECT_EQ(getFirstTriple(query2),
+            "{s: <http://example.org/root>,"
+            " p: <http://example.org/something/p>,"
+            " o: <http://other.example.org/p>}");
+
+  // Cascading prefixes
+  auto query3 = SparqlParser::parseQuery(
+      "BASE <http://example.org/> "
+      "PREFIX ex1: <ex1/> "
+      "BASE <http://other.example.org/> "
+      "PREFIX ex2: <ex2/> "
+      "BASE <http://alternative.example.org/> "
+      "SELECT * WHERE { ex2:hello <world> ex1:test }");
+  EXPECT_EQ(getFirstTriple(query3),
+            "{s: <http://other.example.org/ex2/hello>,"
+            " p: <http://alternative.example.org/world>,"
+            " o: <http://example.org/ex1/test>}");
+
+  AD_EXPECT_THROW_WITH_MESSAGE_AND_TYPE(
+      SparqlParser::parseQuery("BASE <http://example.com> BASE <relative> "
+                               "SELECT * WHERE { ?s ?p ?o }"),
+      ::testing::HasSubstr("absolute IRI"), InvalidSparqlQueryException);
+}