Account for static blockers in frontier reachability

libs/s25main/pathfinding/FindPathReachable.cpp

@@ -6,10 +6,31 @@
 #include "pathfinding/FreePathFinderImpl.h"
 #include "pathfinding/PathConditionReachable.h"
 #include "world/GameWorldBase.h"
+#include "nodeObjs/noBase.h"
+
+namespace {
+
+// Keep this narrower than PathConditionHuman, but reject permanently blocking static objects:
+// Human pathing can never accept them and they cannot be removed.
+struct PathConditionReachableWithStaticBlockers : PathConditionReachable
+{
+    PathConditionReachableWithStaticBlockers(const World& world) : PathConditionReachable(world) {}
+
+    BOOST_FORCEINLINE bool IsNodeOk(const MapPoint& pt) const
+    {
+        const auto* obj = world.GetNode(pt).obj;
+        if(obj && obj->GetGOT() == GO_Type::Staticobject && obj->GetBM() != BlockingManner::None)
+            return false;
+
+        return PathConditionReachable::IsNodeOk(pt);
+    }
+};
+
+} // namespace
 
 bool DoesReachablePathExist(const GameWorldBase& world, const MapPoint startPt, const MapPoint endPt, unsigned maxLen)
 {
     RTTR_Assert(startPt != endPt);
     return world.GetFreePathFinder().FindPath(startPt, endPt, false, maxLen, nullptr, nullptr, nullptr,
-                                              PathConditionReachable(world));
+                                              PathConditionReachableWithStaticBlockers(world));
 }

tests/s25Main/integration/testFrontierDistance.cpp

@@ -3,14 +3,18 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
 
 #include "GamePlayer.h"
+#include "RttrForeachPt.h"
 #include "buildings/nobMilitary.h"
 #include "factories/BuildingFactory.h"
 #include "helpers/Range.h"
+#include "pathfinding/FindPathReachable.h"
 #include "worldFixtures/CreateEmptyWorld.h"
 #include "worldFixtures/CreateSeaWorld.h"
 #include "worldFixtures/WorldFixture.h"
 #include "worldFixtures/terrainHelpers.h"
 #include "world/MapLoader.h"
+#include "nodeObjs/noEnvObject.h"
+#include "nodeObjs/noStaticObject.h"
 #include <boost/test/unit_test.hpp>
 #include <stdexcept>
 
@@ -56,6 +60,7 @@ using FrontierWorldSmall = FrontierWorld<34u, 20u>;
 using FrontierWorldMiddle = FrontierWorld<38u, 20u>;
 using FrontierWorldBig = FrontierWorld<60u, 20u>;
 using FrontierWorldSea = FrontierWorld<SmallSeaWorldDefault<2>::width, SmallSeaWorldDefault<2>::height, CreateSeaWorld>;
+using FrontierWorldStaticBlocker = WorldFixture<CreateEmptyWorld, 0, 20u, 12u>;
 
 } // namespace
 
@@ -347,4 +352,51 @@ BOOST_FIXTURE_TEST_CASE(FrontierDistanceBug_815, WorldBig)
     BOOST_TEST_REQUIRE(distance1 == FrontierDistance::Near);
 }
 
+BOOST_FIXTURE_TEST_CASE(FrontierDistanceReachabilityConsidersStaticObjectBlockers, FrontierWorldStaticBlocker)
+{
+    const DescIdx<TerrainDesc> tWater = GetWaterTerrain(world.GetDescription());
+    const unsigned corridorY = 6;
+    const MapPoint startPt(2, corridorY);
+    const MapPoint endPt(10, corridorY);
+    constexpr unsigned maxPathLen = 8;
+
+    RTTR_FOREACH_PT(MapPoint, world.GetSize())
+    {
+        if(pt.y == corridorY && pt.x >= startPt.x && pt.x <= endPt.x)
+            continue;
+
+        MapNode& node = world.GetNodeWriteable(pt);
+        node.t1 = tWater;
+        node.t2 = tWater;
+    }
+
+    BOOST_TEST_REQUIRE(DoesReachablePathExist(world, startPt, endPt, maxPathLen));
+
+    for(const unsigned x : helpers::range<MapCoord>(startPt.x + 1, endPt.x))
+    {
+        const MapPoint passablePt(x, corridorY);
+        world.DestroyNO(passablePt, false);
+        world.SetNO(passablePt, new noStaticObject(passablePt, 0, 0, 0));
+    }
+
+    BOOST_TEST_REQUIRE(DoesReachablePathExist(world, startPt, endPt, maxPathLen));
+
+    for(const unsigned x : helpers::range<MapCoord>(startPt.x + 1, endPt.x))
+    {
+        const MapPoint passablePt(x, corridorY);
+        world.DestroyNO(passablePt, false);
+        world.SetNO(passablePt, new noEnvObject(passablePt, 0, 0));
+    }
+
+    BOOST_TEST_REQUIRE(DoesReachablePathExist(world, startPt, endPt, maxPathLen));
+
+    for(const unsigned x : helpers::range<MapCoord>(startPt.x + 1, endPt.x))
+    {
+        const MapPoint blockerPt(x, corridorY);
+        world.DestroyNO(blockerPt, false);
+        world.SetNO(blockerPt, new noStaticObject(blockerPt, 0, 0, 1));
+    }
+
+    BOOST_TEST_REQUIRE(!DoesReachablePathExist(world, startPt, endPt, maxPathLen));
+}
 BOOST_AUTO_TEST_SUITE_END()