print tracebacks and line numbers for Lua runtime errors

include/extractor/scripting_environment_lua.hpp

@@ -41,10 +41,10 @@ struct LuaScriptingContext final
     bool has_way_function = false;
     bool has_segment_function = false;
 
-    sol::function turn_function;
-    sol::function way_function;
-    sol::function node_function;
-    sol::function segment_function;
+    sol::protected_function turn_function;
+    sol::protected_function way_function;
+    sol::protected_function node_function;
+    sol::protected_function segment_function;
 
     int api_version = 4;
     sol::table profile_table;

src/extractor/scripting_environment_lua.cpp

@@ -91,6 +91,19 @@ struct to_lua_object : public boost::static_visitor<sol::object>
 };
 } // namespace
 
+// Handle a lua error thrown in a protected function by printing the traceback and bubbling
+// exception up to caller. Lua errors are generally unrecoverable, so this exception should not be
+// caught but instead should terminate the process. The point of having this error handler rather
+// than just using unprotected Lua functions which terminate the process automatically is that this
+// function provides more useful error messages including Lua tracebacks and line numbers.
+void handle_lua_error(sol::protected_function_result &luares)
+{
+    sol::error luaerr = luares;
+    std::string msg = luaerr.what();
+    std::cerr << msg << std::endl;
+    throw util::exception("Lua error (see stderr for traceback)");
+}
+
 Sol2ScriptingEnvironment::Sol2ScriptingEnvironment(
     const std::string &file_name,
     const std::vector<boost::filesystem::path> &location_dependent_data_paths)
@@ -232,7 +245,8 @@ void Sol2ScriptingEnvironment::InitContext(LuaScriptingContext &context)
                                                  "valid",
                                                  &osmium::Location::valid);
 
-    auto get_location_tag = [](auto &context, const auto &location, const char *key) {
+    auto get_location_tag = [](auto &context, const auto &location, const char *key)
+    {
         if (context.location_dependent_data.empty())
             return sol::object(context.state);
 
@@ -259,7 +273,8 @@ void Sol2ScriptingEnvironment::InitContext(LuaScriptingContext &context)
         "get_nodes",
         [](const osmium::Way &way) { return sol::as_table(&way.nodes()); },
         "get_location_tag",
-        [&context, &get_location_tag](const osmium::Way &way, const char *key) {
+        [&context, &get_location_tag](const osmium::Way &way, const char *key)
+        {
             // HEURISTIC: use a single node (last) of the way to localize the way
             // For more complicated scenarios a proper merging of multiple tags
             // at one or many locations must be provided
@@ -279,9 +294,8 @@ void Sol2ScriptingEnvironment::InitContext(LuaScriptingContext &context)
         "version",
         &osmium::Node::version,
         "get_location_tag",
-        [&context, &get_location_tag](const osmium::Node &node, const char *key) {
-            return get_location_tag(context, node.location(), key);
-        });
+        [&context, &get_location_tag](const osmium::Node &node, const char *key)
+        { return get_location_tag(context, node.location(), key); });
 
     context.state.new_enum("traffic_lights",
                            "none",
@@ -297,7 +311,8 @@ void Sol2ScriptingEnvironment::InitContext(LuaScriptingContext &context)
         "ResultNode",
         "traffic_lights",
         sol::property([](const ExtractionNode &node) { return node.traffic_lights; },
-                      [](ExtractionNode &node, const sol::object &obj) {
+                      [](ExtractionNode &node, const sol::object &obj)
+                      {
                           if (obj.is<bool>())
                           {
                               // The old approach of assigning a boolean traffic light
@@ -348,7 +363,8 @@ void Sol2ScriptingEnvironment::InitContext(LuaScriptingContext &context)
         sol::property(&ExtractionWay::GetName, &ExtractionWay::SetName),
         "ref", // backward compatibility
         sol::property(&ExtractionWay::GetForwardRef,
-                      [](ExtractionWay &way, const char *ref) {
+                      [](ExtractionWay &way, const char *ref)
+                      {
                           way.SetForwardRef(ref);
                           way.SetBackwardRef(ref);
                       }),
@@ -407,7 +423,8 @@ void Sol2ScriptingEnvironment::InitContext(LuaScriptingContext &context)
         sol::property([](const ExtractionWay &way) { return way.access_turn_classification; },
                       [](ExtractionWay &way, int flag) { way.access_turn_classification = flag; }));
 
-    auto getTypedRefBySol = [](const sol::object &obj) -> ExtractionRelation::OsmIDTyped {
+    auto getTypedRefBySol = [](const sol::object &obj) -> ExtractionRelation::OsmIDTyped
+    {
         if (obj.is<osmium::Way>())
         {
             osmium::Way *way = obj.as<osmium::Way *>();
@@ -443,20 +460,19 @@ void Sol2ScriptingEnvironment::InitContext(LuaScriptingContext &context)
         "get_value_by_key",
         [](ExtractionRelation &rel, const char *key) -> const char * { return rel.GetAttr(key); },
         "get_role",
-        [&getTypedRefBySol](ExtractionRelation &rel, const sol::object &obj) -> const char * {
-            return rel.GetRole(getTypedRefBySol(obj));
-        });
+        [&getTypedRefBySol](ExtractionRelation &rel, const sol::object &obj) -> const char *
+        { return rel.GetRole(getTypedRefBySol(obj)); });
 
     context.state.new_usertype<ExtractionRelationContainer>(
         "ExtractionRelationContainer",
         "get_relations",
         [&getTypedRefBySol](ExtractionRelationContainer &cont, const sol::object &obj)
-            -> const ExtractionRelationContainer::RelationIDList & {
-            return cont.GetRelations(getTypedRefBySol(obj));
-        },
+            -> const ExtractionRelationContainer::RelationIDList &
+        { return cont.GetRelations(getTypedRefBySol(obj)); },
         "relation",
-        [](ExtractionRelationContainer &cont, const ExtractionRelation::OsmIDTyped &rel_id)
-            -> const ExtractionRelation & { return cont.GetRelationData(rel_id); });
+        [](ExtractionRelationContainer &cont,
+           const ExtractionRelation::OsmIDTyped &rel_id) -> const ExtractionRelation &
+        { return cont.GetRelationData(rel_id); });
 
     context.state.new_usertype<ExtractionSegment>("ExtractionSegment",
                                                   "source",
@@ -472,10 +488,12 @@ void Sol2ScriptingEnvironment::InitContext(LuaScriptingContext &context)
 
     // Keep in mind .location is available only if .pbf is preprocessed to set the location with the
     // ref using osmium command "osmium add-locations-to-ways"
-    context.state.new_usertype<osmium::NodeRef>(
-        "NodeRef", "id", &osmium::NodeRef::ref, "location", [](const osmium::NodeRef &nref) {
-            return nref.location();
-        });
+    context.state.new_usertype<osmium::NodeRef>("NodeRef",
+                                                "id",
+                                                &osmium::NodeRef::ref,
+                                                "location",
+                                                [](const osmium::NodeRef &nref)
+                                                { return nref.location(); });
 
     context.state.new_usertype<InternalExtractorEdge>("EdgeSource",
                                                       "source_coordinate",
@@ -531,7 +549,8 @@ void Sol2ScriptingEnvironment::InitContext(LuaScriptingContext &context)
     util::Log() << "Using profile api version " << context.api_version;
 
     // version-dependent parts of the api
-    auto initV2Context = [&]() {
+    auto initV2Context = [&]()
+    {
         // clear global not used in v2
         context.state["properties"] = sol::nullopt;
 
@@ -550,10 +569,16 @@ void Sol2ScriptingEnvironment::InitContext(LuaScriptingContext &context)
                                std::numeric_limits<TurnPenalty::value_type>::max());
 
         // call initialize function
-        sol::function setup_function = function_table.value()["setup"];
+        sol::protected_function setup_function = function_table.value()["setup"];
         if (!setup_function.valid())
             throw util::exception("Profile must have an setup() function.");
-        sol::optional<sol::table> profile_table = setup_function();
+
+        auto setup_result = setup_function();
+
+        if (!setup_result.valid())
+            handle_lua_error(setup_result);
+
+        sol::optional<sol::table> profile_table = setup_result;
         if (profile_table == sol::nullopt)
             throw util::exception("Profile setup() must return a table.");
         else
@@ -616,13 +641,16 @@ void Sol2ScriptingEnvironment::InitContext(LuaScriptingContext &context)
         }
     };
 
-    auto initialize_V3_extraction_turn = [&]() {
+    auto initialize_V3_extraction_turn = [&]()
+    {
         context.state.new_usertype<ExtractionTurn>(
             "ExtractionTurn",
             "angle",
             &ExtractionTurn::angle,
             "turn_type",
-            sol::property([](const ExtractionTurn &turn) {
+            sol::property(
+                [](const ExtractionTurn &turn)
+                {
                     if (turn.number_of_roads > 2 || turn.source_mode != turn.target_mode ||
                         turn.is_u_turn)
                         return osrm::guidance::TurnType::Turn;
@@ -630,7 +658,9 @@ void Sol2ScriptingEnvironment::InitContext(LuaScriptingContext &context)
                         return osrm::guidance::TurnType::NoTurn;
                 }),
             "direction_modifier",
-            sol::property([](const ExtractionTurn &turn) {
+            sol::property(
+                [](const ExtractionTurn &turn)
+                {
                     if (turn.is_u_turn)
                         return osrm::guidance::DirectionModifier::UTurn;
                     else
@@ -845,10 +875,12 @@ void Sol2ScriptingEnvironment::InitContext(LuaScriptingContext &context)
         BOOST_ASSERT(context.properties.GetTrafficSignalPenalty() == 0);
 
         // call source_function if present
-        sol::function source_function = context.state["source_function"];
+        sol::protected_function source_function = context.state["source_function"];
         if (source_function.valid())
         {
-            source_function();
+            auto luares = source_function();
+            if (!luares.valid())
+                handle_lua_error(luares);
         }
 
         break;
@@ -961,10 +993,12 @@ Sol2ScriptingEnvironment::GetStringListFromFunction(const std::string &function_
     auto &context = GetSol2Context();
     BOOST_ASSERT(context.state.lua_state());
     std::vector<std::string> strings;
-    sol::function function = context.state[function_name];
+    sol::protected_function function = context.state[function_name];
     if (function.valid())
     {
-        function(strings);
+        auto luares = function(strings);
+        if (!luares.valid())
+            handle_lua_error(luares);
     }
     return strings;
 }
@@ -1123,7 +1157,9 @@ void Sol2ScriptingEnvironment::ProcessTurn(ExtractionTurn &turn)
     case 2:
         if (context.has_turn_penalty_function)
         {
-            context.turn_function(context.profile_table, std::ref(turn));
+            auto luares = context.turn_function(context.profile_table, std::ref(turn));
+            if (!luares.valid())
+                handle_lua_error(luares);
 
             // Turn weight falls back to the duration value in deciseconds
             // or uses the extracted unit-less weight value
@@ -1138,7 +1174,9 @@ void Sol2ScriptingEnvironment::ProcessTurn(ExtractionTurn &turn)
     case 1:
         if (context.has_turn_penalty_function)
         {
-            context.turn_function(std::ref(turn));
+            auto luares = context.turn_function(std::ref(turn));
+            if (!luares.valid())
+                handle_lua_error(luares);
 
             // Turn weight falls back to the duration value in deciseconds
             // or uses the extracted unit-less weight value
@@ -1184,24 +1222,28 @@ void Sol2ScriptingEnvironment::ProcessSegment(ExtractionSegment &segment)
 
     if (context.has_segment_function)
     {
+        sol::protected_function_result luares;
         switch (context.api_version)
         {
         case 4:
         case 3:
         case 2:
-            context.segment_function(context.profile_table, std::ref(segment));
+            luares = context.segment_function(context.profile_table, std::ref(segment));
             break;
         case 1:
-            context.segment_function(std::ref(segment));
+            luares = context.segment_function(std::ref(segment));
             break;
         case 0:
-            context.segment_function(std::ref(segment.source),
+            luares = context.segment_function(std::ref(segment.source),
                                               std::ref(segment.target),
                                               segment.distance,
                                               segment.duration);
             segment.weight = segment.duration; // back-compatibility fallback to duration
             break;
         }
+
+        if (!luares.valid())
+            handle_lua_error(luares);
     }
 }
 
@@ -1211,20 +1253,27 @@ void LuaScriptingContext::ProcessNode(const osmium::Node &node,
 {
     BOOST_ASSERT(state.lua_state() != nullptr);
 
+    sol::protected_function_result luares;
+
+    // TODO check for api version, make sure luares is always set
     switch (api_version)
     {
     case 4:
     case 3:
+        luares =
             node_function(profile_table, std::cref(node), std::ref(result), std::cref(relations));
         break;
     case 2:
-        node_function(profile_table, std::cref(node), std::ref(result));
+        luares = node_function(profile_table, std::cref(node), std::ref(result));
         break;
     case 1:
     case 0:
-        node_function(std::cref(node), std::ref(result));
+        luares = node_function(std::cref(node), std::ref(result));
         break;
     }
+
+    if (!luares.valid())
+        handle_lua_error(luares);
 }
 
 void LuaScriptingContext::ProcessWay(const osmium::Way &way,
@@ -1233,20 +1282,27 @@ void LuaScriptingContext::ProcessWay(const osmium::Way &way,
 {
     BOOST_ASSERT(state.lua_state() != nullptr);
 
+    sol::protected_function_result luares;
+
+    // TODO check for api version, make sure luares is always set
     switch (api_version)
     {
     case 4:
     case 3:
+        luares =
             way_function(profile_table, std::cref(way), std::ref(result), std::cref(relations));
         break;
     case 2:
-        way_function(profile_table, std::cref(way), std::ref(result));
+        luares = way_function(profile_table, std::cref(way), std::ref(result));
         break;
     case 1:
     case 0:
-        way_function(std::cref(way), std::ref(result));
+        luares = way_function(std::cref(way), std::ref(result));
         break;
     }
+
+    if (!luares.valid())
+        handle_lua_error(luares);
 }
 
 } // namespace osrm::extractor