Subgraph link throws when subgraph is nested too deep

.github/workflows/build-and-test.yml

@@ -16,24 +16,23 @@ on:
 jobs:
   build-and-test:
     runs-on: ubuntu-latest
-
     steps:
     - name: Checkout code
-      uses: actions/checkout@v4
+      uses: actions/checkout@v7
 
     - name: Setup .NET
-      uses: actions/setup-dotnet@v4
+      uses: actions/setup-dotnet@v6
       with:
-        dotnet-version: 9.0.x
+        dotnet-version: |
+          8.0.x
+          9.0.x
+          10.0.x
 
     - name: Check formatter rules
       run: dotnet format --verify-no-changes --verbosity diagnostic
 
-    - name: Restore dependencies
-      run: dotnet restore
-
     - name: Build
-      run: dotnet build --no-restore
+      run: dotnet build
 
     - name: Test
       run: dotnet test --no-build --verbosity normal

src/Mermaid.Flowcharts/Flowchart.cs

@@ -42,12 +42,18 @@ public Flowchart AddNode(INode node)
 
     public Flowchart AddLink(Link link)
     {
-        if (AllNodeChildren.Any(link.Source.Equals) && AllNodeChildren.Any(link.Destination.Equals))
+        if (!AllNodeChildren.Any(link.Source.Equals))
         {
-            _links.Add(link);
-            return this;
+            throw new InvalidOperationException("Cannot add link to flowchart: the source node should be present within the flowchart.");
+        }
+
+        if (!AllNodeChildren.Any(link.Destination.Equals))
+        {
+            throw new InvalidOperationException("Cannot add link to flowchart: the destination node should be present within the flowchart.");
         }
-        throw new InvalidOperationException("Cannot add link to flowchart: the source and the destination nodes should both be present within the flowchart.");
+
+        _links.Add(link);
+        return this;
     }
 
     public override string ToString()

src/Mermaid.Flowcharts/Subgraphs/Subgraph.cs

@@ -16,7 +16,7 @@ public record Subgraph : INode<Subgraph>
     public IEnumerable<Node> Nodes => _nodes.OfType<Node>();
     public IEnumerable<Subgraph> Subgraphs => _nodes.OfType<Subgraph>();
     public IEnumerable<Link> Links => _links.AsReadOnly();
-    public IEnumerable<INode> AllNodeChildren => _nodes.Concat(Subgraphs.SelectMany(subgraph => subgraph._nodes));
+    public IEnumerable<INode> AllNodeChildren => _nodes.Concat(Subgraphs.SelectMany(subgraph => subgraph.AllNodeChildren));
     public IEnumerable<Node> AllNodes => Nodes.Concat(Subgraphs.SelectMany(subgraph => subgraph.AllNodes));
     public IEnumerable<Link> AllLinks => Links.Concat(Subgraphs.SelectMany(subgraph => subgraph.AllLinks));
 

tests/Mermaid.Flowcharts.Tests/FlowchartTests.cs

@@ -123,7 +123,7 @@ public void Flowchart_WhenLinkSourceNotPresent_AddLinkShouldThrow()
         InvalidOperationException exception = Assert.Throws<InvalidOperationException>(
             () => flowchart.AddLink(link)
         );
-        Assert.Contains("Cannot add link to flowchart: the source and the destination nodes should both be present within the flowchart.", exception.Message);
+        Assert.Contains("Cannot add link to flowchart: the source node should be present within the flowchart.", exception.Message);
     }
 
     [Fact]
@@ -140,7 +140,7 @@ public void Flowchart_WhenLinkDestinationNotPresent_AddLinkShouldThrow()
         InvalidOperationException exception = Assert.Throws<InvalidOperationException>(
             () => flowchart.AddLink(link)
         );
-        Assert.Contains("Cannot add link to flowchart: the source and the destination nodes should both be present within the flowchart.", exception.Message);
+        Assert.Contains("Cannot add link to flowchart: the destination node should be present within the flowchart.", exception.Message);
     }
 
     [Fact]
@@ -805,4 +805,80 @@ subgraph ssg ["Subsubgraph"]
         // Assert
         Assert.Equal(expected, actual);
     }
+
+    [Fact]
+    public void Flowchart_ShouldLinkToNodeThreeSubgraphLevelsDeep()
+    {
+        Flowchart flowchart = new();
+        Node top = Node.Create("top", "Top");
+        Subgraph outer = Subgraph.Create("outer", "Outer");
+        Subgraph middle = Subgraph.Create("middle", "Middle");
+        Subgraph inner = Subgraph.Create("inner", "Inner");
+        Node deep = Node.Create("deep", "Deep");
+
+        inner.AddNode(deep);
+        middle.AddNode(inner);
+        outer.AddNode(middle);
+        flowchart.AddNode(top).AddNode(outer);
+        flowchart.AddLink(Link.Create(top, deep));
+
+        string expected =
+            """
+            flowchart TD
+                top["Top"]
+
+                subgraph outer ["Outer"]
+
+                    subgraph middle ["Middle"]
+
+                        subgraph inner ["Inner"]
+                            deep["Deep"]
+                        end
+                    end
+                end
+
+                top ---> deep
+
+            """;
+
+        Assert.Equal(expected, flowchart.ToMermaidString(0, "    "));
+    }
+
+    [Fact]
+    public void Subgraph_ShouldLinkToNodeNestedInsideInnerSubgraph()
+    {
+        Flowchart flowchart = new();
+        Node a = Node.Create("a", "A");
+        Subgraph outer = Subgraph.Create("outer", "Outer");
+        Subgraph middle = Subgraph.Create("middle", "Middle");
+        Subgraph inner = Subgraph.Create("inner", "Inner");
+        Node deep = Node.Create("deep", "Deep");
+
+        inner.AddNode(deep);
+        middle.AddNode(inner);
+        outer.AddNode(a).AddNode(middle);
+        flowchart.AddNode(outer);
+        outer.AddLink(Link.Create(a, deep));
+
+        string expected =
+            """
+            flowchart TD
+
+                subgraph outer ["Outer"]
+                    a["A"]
+
+                    subgraph middle ["Middle"]
+
+                        subgraph inner ["Inner"]
+                            deep["Deep"]
+                        end
+                    end
+
+                    a ---> deep
+                end
+
+            """;
+
+        Assert.Equal(expected, flowchart.ToMermaidString(0, "    "));
+    }
 }