From 4ae1bf08d05266c1d0f8060ca66eb066749ba462 Mon Sep 17 00:00:00 2001
From: Dima Enns <dieter.enns@gmail.com>
Date: Fri, 26 Jan 2024 11:14:01 +0100
Subject: [PATCH] Implement generation of primary constructors for nested types

---
 PrimaryConstructor.Sample/Program.cs          | 12 ++++
 .../PrimaryConstructorGenerator.cs            | 59 ++++++++++++++++---
 2 files changed, 63 insertions(+), 8 deletions(-)

diff --git a/PrimaryConstructor.Sample/Program.cs b/PrimaryConstructor.Sample/Program.cs
index 4e5911b..dd503c4 100644
--- a/PrimaryConstructor.Sample/Program.cs
+++ b/PrimaryConstructor.Sample/Program.cs
@@ -87,4 +87,16 @@ public string GetName()
     public class NotRegisteredDependency
     {
     }
+
+    public partial class NestingGrandMother
+    {
+        public partial class NestingFather
+        {
+            [PrimaryConstructor]
+            public partial class Nested
+            {
+                private readonly int _dummy;
+            }
+        }
+    }
 }
\ No newline at end of file
diff --git a/PrimaryConstructor/PrimaryConstructorGenerator.cs b/PrimaryConstructor/PrimaryConstructorGenerator.cs
index b6faa2f..6bec83d 100644
--- a/PrimaryConstructor/PrimaryConstructorGenerator.cs
+++ b/PrimaryConstructor/PrimaryConstructorGenerator.cs
@@ -37,8 +37,15 @@ public void Execute(GeneratorExecutionContext context)
                 classNames.TryGetValue(classSymbol.Name, out var i);
                 var name = i == 0 ? classSymbol.Name : $"{classSymbol.Name}{i + 1}";
                 classNames[classSymbol.Name] = i + 1;
-                context.AddSource($"{name}.PrimaryConstructor.g.cs",
-                    SourceText.From(CreatePrimaryConstructor(classSymbol), Encoding.UTF8));
+                
+                var source = CSharpSyntaxTree
+                    .ParseText(SourceText.From(CreatePrimaryConstructor(classSymbol), Encoding.UTF8))
+                    .GetRoot()
+                    .NormalizeWhitespace()
+                    .SyntaxTree
+                    .GetText();
+                
+                context.AddSource($"{name}.PrimaryConstructor.g.cs", source);
             }
         }
 
@@ -89,12 +96,21 @@ private static string CreatePrimaryConstructor(INamedTypeSymbol classSymbol)
             var memberList = GetMembers(classSymbol, false);
             var arguments = (baseClassConstructorArgs == null ? memberList : memberList.Concat(baseClassConstructorArgs))
                 .Select(it => $"{it.Type} {it.ParameterName}");
-            var fullTypeName = classSymbol.ToDisplayString(TypeFormat);
-            var i = fullTypeName.IndexOf('<');
-            var generic = i < 0 ? "" : fullTypeName.Substring(i);
+            var nestingStack = GetNestingAncestors(classSymbol);
+            var nestingCount = nestingStack.Count;
             var source = new StringBuilder($@"namespace {namespaceName}
-{{
-    partial class {classSymbol.Name}{generic}
+{{");
+            while (nestingStack.Any())
+            {
+                var currentNestingAncestor = nestingStack.Pop();
+
+                source.Append($@"
+    partial class {currentNestingAncestor.Name}{GetGenericsNamePart(currentNestingAncestor)}
+    {{");
+            }
+            
+            source.Append($@"
+    partial class {classSymbol.Name}{GetGenericsNamePart(classSymbol)}
     {{
         public {classSymbol.Name}({string.Join(", ", arguments)}){baseConstructorInheritance}
         {{");
@@ -104,9 +120,18 @@ partial class {classSymbol.Name}{generic}
                 source.Append($@"
             this.{item.Name} = {item.ParameterName};");
             }
+
             source.Append(@"
         }
-    }
+    }");
+
+            for (int i = 0; i < nestingCount; i++)
+            {
+                source.Append(@"
+    }");
+            }
+            
+            source.Append(@"
 }
 ");
 
@@ -177,5 +202,23 @@ select model.GetDeclaredSymbol(clazz)! into classSymbol
                 where HasAttribute(classSymbol, nameof(PrimaryConstructorAttribute))
                 select classSymbol;
         }
+
+        private static Stack<INamedTypeSymbol> GetNestingAncestors(INamedTypeSymbol classSymbol)
+        {
+            var stack = new Stack<INamedTypeSymbol>();
+            var current = classSymbol.ContainingType;
+            while (current is not null)
+            {
+                stack.Push(current);
+                current = current.ContainingType;
+            }
+
+            return stack;
+        }
+
+        private static string GetGenericsNamePart(INamedTypeSymbol classSymbol) =>
+            classSymbol.TypeArguments.Any()
+                ? $"<{string.Join(", ", classSymbol.TypeArguments.Select(s => s.ToDisplayString(TypeFormat)))}>"
+                : "";
     }
 }