From eaf2ed4e4ee86846816349311575ddd7c64b0247 Mon Sep 17 00:00:00 2001
From: Jose <jose@zeroc.com>
Date: Mon, 27 Apr 2026 15:57:10 +0200
Subject: [PATCH] Dedup partial service-class declarations in the generator

ForAttributeWithMetadataName emits one ClassDeclarationSyntax per
attribute application. If a user puts [Service] on more than one
partial part of the same class, the parser previously processed every
syntax node and the generator called AddSource twice with the same
hint name, which Roslyn rejects with an opaque generator-threw
ArgumentException at build time.

Track classes by their resolved INamedTypeSymbol and skip ones we've
already processed. The user's intent is unambiguous (the parts
together are one class), so silent dedup is the natural behavior; no
diagnostic is needed.
---
 src/IceRpc.ServiceGenerator/Internal/Parser.cs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/IceRpc.ServiceGenerator/Internal/Parser.cs b/src/IceRpc.ServiceGenerator/Internal/Parser.cs
index 210825f19..6755660f1 100644
--- a/src/IceRpc.ServiceGenerator/Internal/Parser.cs
+++ b/src/IceRpc.ServiceGenerator/Internal/Parser.cs
@@ -43,6 +43,10 @@ internal IReadOnlyList<ServiceClass> GetServiceDefinitions(IEnumerable<ClassDecl
         }
 
         var serviceDefinitions = new List<ServiceClass>();
+        // Multiple partial declarations of the same class with [Service] applied to more than one part each yield
+        // their own ClassDeclarationSyntax from ForAttributeWithMetadataName. Process each class symbol once so we
+        // don't AddSource the same hint name twice.
+        var seenClassSymbols = new HashSet<INamedTypeSymbol>(SymbolEqualityComparer.Default);
         // we enumerate by syntax tree, to minimize the need to instantiate semantic models (since they're expensive)
         foreach (IGrouping<SyntaxTree, ClassDeclarationSyntax> group in classes.GroupBy(x => x.SyntaxTree))
         {
@@ -53,7 +57,7 @@ internal IReadOnlyList<ServiceClass> GetServiceDefinitions(IEnumerable<ClassDecl
 
                 SemanticModel semanticModel = _compilation.GetSemanticModel(classDeclaration.SyntaxTree);
                 INamedTypeSymbol? classSymbol = semanticModel.GetDeclaredSymbol(classDeclaration, _cancellationToken);
-                if (classSymbol is null)
+                if (classSymbol is null || !seenClassSymbols.Add(classSymbol))
                 {
                     continue;
                 }