Added support for generating many to many relations in mermaid-er-dia…

…gram-from-efcore (#133)

docs/templates/releasenotes/yyyy-MM-dd-v-x.y.z.md

@@ -4,7 +4,8 @@
 
 ### Improvements in this version
 ## Prerelease 2
-- Added support for generating many to many association in `mermaid-class-diagram-from-csharp`.
+- Added support for generating many to many associations in `mermaid-class-diagram-from-csharp`.
+- Added support for generating many to many relations in `mermaid-er-diagram-from-csharp`.
 ## Prerelease 1 (2024-10-29)
 - Fixed an issue where  `mermaid-er-diagram-from-efcore` would fail when an input assebly referenced Asp.Net Core. 
    - Ie the .csproj file contained `<Project Sdk="Microsoft.NET.Sdk.Web">` or `<FrameworkReference Include="Microsoft.AspNetCore.App|All">` or referenced such an assembly.

src/DryGen.MermaidFromCSharp/ErDiagram/ErDiagramEntity.cs

@@ -34,8 +34,13 @@ public void AddAttribute(ErDiagramAttribute attribute)
 
     public void AddRelationship(ErDiagramEntity to, ErDiagramRelationshipCardinality fromCardinality, ErDiagramRelationshipCardinality toCardinality, string label, string propertyName, bool isIdentifying = false)
     {
-        var relationShip = new ErDiagramRelationship(to, fromCardinality, toCardinality, label, propertyName, isIdentifying);
-        relationships.Add(relationShip);
+        var relationship = new ErDiagramRelationship(to, fromCardinality, toCardinality, label, propertyName, isIdentifying);
+        relationships.Add(relationship);
+    }
+
+    public void RemoveRelationship(ErDiagramRelationship relationship)
+    {
+        relationships.Remove(relationship);
     }
 
     public void RemoveBidirectionalRelationshipDuplicates()
@@ -47,6 +52,25 @@ public void RemoveBidirectionalRelationshipDuplicates()
                 || r.To.GetRelationships().Any(x => x.To == this)));
     }
 
+public void MergeTwoOneToManyIntoOneMayToMany()
+    {
+        bool wasModified;
+        do
+        {
+            // Must use an outer loop since a self referencing many to many will modify the relationships collection and the enumeration will crash
+            wasModified = false;
+            foreach (var relationship in relationships.Where(x => x.FromCardinality == ErDiagramRelationshipCardinality.ExactlyOne && x.ToCardinality == ErDiagramRelationshipCardinality.ZeroOrMore && ! x.IsIdenifying)) {
+                var backRelationship = relationship.To.Relationships.FirstOrDefault(x => x.To == this && x.FromCardinality == ErDiagramRelationshipCardinality.ExactlyOne && x.ToCardinality == ErDiagramRelationshipCardinality.ZeroOrMore && ! x.IsIdenifying && x != relationship);
+                if (backRelationship == null) {
+                    continue;
+                }
+                relationship.MergeAsManyToManyWith(backRelationship);
+                wasModified = true;
+                break;
+            }
+        } while (wasModified);
+    }
+
     protected override bool IsRelatedTo(IDiagramType type)
     {
         var result = relationships.Exists(x => x.To.Type == type.Type);

src/DryGen.MermaidFromCSharp/ErDiagram/ErDiagramRelationship.cs

@@ -19,9 +19,14 @@ public ErDiagramRelationship(
     }
 
     public ErDiagramEntity To { get; }
-    public ErDiagramRelationshipCardinality FromCardinality { get; }
+    public ErDiagramRelationshipCardinality FromCardinality { get; private set; }
     public ErDiagramRelationshipCardinality ToCardinality { get; }
     public string Label { get; }
     internal string PropertyName { get; }
     public bool IsIdenifying { get; }
+
+    public void MergeAsManyToManyWith(ErDiagramRelationship backRelationship) {
+        FromCardinality = ErDiagramRelationshipCardinality.ZeroOrMore;
+        To.RemoveRelationship(backRelationship);
+    }
 }

src/DryGen.MermaidFromCSharp/ErDiagram/ErDiagramStructureBuilderByReflection.cs

@@ -36,7 +36,8 @@ private static void GeneratieErStructure(IList<ErDiagramEntity> entities, IReadO
                     var genericArgumentPropertyType = propertyType.GetGenericArguments()[0];
                     if (entityLookup.TryGetValue(genericArgumentPropertyType, out var toEntity))
                     {
-                        entity.AddRelationship(toEntity, ErDiagramRelationshipCardinality.ExactlyOne, ErDiagramRelationshipCardinality.ZeroOrMore, string.Empty, property.Name);
+                        var label = property.Name.Contains(toEntity.Name) ? string.Empty : property.Name.ToNormalizedRelationshipLabel();
+                        entity.AddRelationship(toEntity, ErDiagramRelationshipCardinality.ExactlyOne, ErDiagramRelationshipCardinality.ZeroOrMore, label, property.Name);
                     }
                 }
                 else if (property.IsErDiagramAttributePropertyType())
@@ -56,6 +57,10 @@ private static void GeneratieErStructure(IList<ErDiagramEntity> entities, IReadO
         {
             entity.RemoveBidirectionalRelationshipDuplicates();
         }
+        foreach (var entity in entities)
+        {
+            entity.MergeTwoOneToManyIntoOneMayToMany();
+        }
         enumEntities.AppendToEntities(entities);
     }
 }

src/develop/DryGen.UTests/Features/Mermaid/FromCSharpAndEfCore/ErDiagram/GeneratingErRelationships.feature

@@ -366,7 +366,7 @@ Scenario: Generates many to many relationship with only one property in the key
 		"""
 Examples:
 	| Structure builder |
-	#| Reflection        |
+	| Reflection        |
 	| EfCore            |
 
 Scenario: Generates many to many relationship with several properties in the key
@@ -412,7 +412,7 @@ Scenario: Generates many to many relationship with several properties in the key
 		"""
 Examples:
 	| Structure builder |
-	#| Reflection        |
+	| Reflection        |
 	| EfCore            |
 
 Scenario: Generates self referencing many to many relationship with only one property in the key
@@ -444,7 +444,7 @@ Scenario: Generates self referencing many to many relationship with only one pro
 		"""
 Examples:
 	| Structure builder |
-	#| Reflection        |
+	| Reflection        |
 	| EfCore            |
 
 Scenario: Generates self referencing many to many relationship with several properties in the key
@@ -482,5 +482,5 @@ Scenario: Generates self referencing many to many relationship with several prop
 		"""
 Examples:
 	| Structure builder |
-	#| Reflection        |
+	| Reflection        |
 	| EfCore            |