Log better error for incorrect Construction Graphs.

Also improves integration tests for them to catch more errors.

Content.IntegrationTests/Tests/Construction/ConstructionPrototypeTest.cs

@@ -1,4 +1,6 @@
+using System.Linq;
 using System.Threading.Tasks;
+using Content.Server.Construction.Components;
 using Content.Shared.Construction.Prototypes;
 using NUnit.Framework;
 using Robust.Shared.Prototypes;
@@ -8,6 +10,9 @@ namespace Content.IntegrationTests.Tests.Construction
     [TestFixture]
     public sealed class ConstructionPrototypeTest : ContentIntegrationTest
     {
+        // discount linter for construction graphs
+        // TODO: Create serialization validators for these?
+
         [Test]
         public async Task TestStartIsValid()
         {
@@ -45,7 +50,7 @@ namespace Content.IntegrationTests.Tests.Construction
         }
 
         [Test]
-        public async Task TestStartReachesTarget()
+        public async Task TestStartReachesValidTarget()
         {
             var server = StartServer();
 
@@ -58,7 +63,12 @@ namespace Content.IntegrationTests.Tests.Construction
                 var start = proto.StartNode;
                 var target = proto.TargetNode;
                 var graph = protoMan.Index<ConstructionGraphPrototype>(proto.Graph);
-                Assert.That(graph.TryPath(start, target, out _), $"Unable to find path from \"{start}\" to \"{target}\" on graph \"{graph.ID}\"");
+                Assert.That(graph.TryPath(start, target, out var path), $"Unable to find path from \"{start}\" to \"{target}\" on graph \"{graph.ID}\"");
+                Assert.That(path!.Length, Is.GreaterThanOrEqualTo(1), $"Unable to find path from \"{start}\" to \"{target}\" on graph \"{graph.ID}\".");
+                var next = path[0];
+                Assert.That(next.Entity, Is.Not.Null, $"The next node ({next.Name}) in the path from the start node ({start}) to the target node ({target}) must specify an entity! Graph: {graph.ID}");
+                Assert.That(protoMan.TryIndex(next.Entity, out EntityPrototype entity), $"The next node ({next.Name}) in the path from the start node ({start}) to the target node ({target}) specified an invalid entity prototype ({next.Entity})");
+                Assert.That(entity.Components.ContainsKey("Construction"), $"The next node ({next.Name}) in the path from the start node ({start}) to the target node ({target}) specified an entity prototype ({next.Entity}) without a ConstructionComponent.");
             }
         }
     }

Content.Server/Construction/ConstructionSystem.Initial.cs

@@ -234,10 +234,15 @@ namespace Content.Server.Construction
                 return null;
             }
 
-            var newEntity = EntityManager.SpawnEntity(graph.Nodes[edge.Target].Entity, EntityManager.GetComponent<TransformComponent>(user).Coordinates);
+            var newEntityProto = graph.Nodes[edge.Target].Entity;
+            var newEntity = EntityManager.SpawnEntity(newEntityProto, EntityManager.GetComponent<TransformComponent>(user).Coordinates);
 
-            // Yes, this should throw if it's missing the component.
+            if (!TryComp(newEntity, out ConstructionComponent? construction))
-            var construction = EntityManager.GetComponent<ConstructionComponent>(newEntity);
+            {
+                _sawmill.Error($"Initial construction does not have a valid target entity! It is missing a ConstructionComponent.\nGraph: {graph.ID}, Initial Target: {edge.Target}, Ent. Prototype: {newEntityProto}\nCreated Entity {ToPrettyString(newEntity)} will be deleted.");
+                Del(newEntity); // Screw you, make proper construction graphs.
+                return null;
+            }
 
             // We attempt to set the pathfinding target.
             SetPathfindingTarget(newEntity, targetNode.Name, construction);