From 03b1a9077ce9ba6b0736278e01fa9671a32a5424 Mon Sep 17 00:00:00 2001
From: "fabien.menager" <fabien.menager@am-creations.fr>
Date: Sun, 1 Mar 2026 09:10:48 +0100
Subject: [PATCH] Check source generator output compilation

---
 .../ProjectionExpressionGeneratorTests.cs     | 38 +++++++++++++++----
 1 file changed, 31 insertions(+), 7 deletions(-)

diff --git a/tests/EntityFrameworkCore.Projectables.Generator.Tests/ProjectionExpressionGeneratorTests.cs b/tests/EntityFrameworkCore.Projectables.Generator.Tests/ProjectionExpressionGeneratorTests.cs
index e5b07d2..0270c86 100644
--- a/tests/EntityFrameworkCore.Projectables.Generator.Tests/ProjectionExpressionGeneratorTests.cs
+++ b/tests/EntityFrameworkCore.Projectables.Generator.Tests/ProjectionExpressionGeneratorTests.cs
@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using System.Linq;
 using System.Threading.Tasks;
@@ -134,8 +135,8 @@ public Task SimpleProjectableComputedInNestedClassProperty()
 using System;
 using EntityFrameworkCore.Projectables;
 namespace Foo {
-    class C {
-        class D {
+    public class C {
+        public class D {
             public int Bar { get; set; }
 
             [Projectable]
@@ -2540,7 +2541,7 @@ public record Entity
 
         #region Helpers
 
-        Compilation CreateCompilation(string source, bool expectedToCompile = true)
+        Compilation CreateCompilation([StringSyntax("csharp")] string source, bool expectedToCompile = true)
         {
             var references = Basic.Reference.Assemblies.
 #if NET10_0
@@ -2592,7 +2593,7 @@ private GeneratorDriverRunResult RunGenerator(Compilation compilation)
             var subject = new ProjectionExpressionGenerator();
             var driver = CSharpGeneratorDriver
                 .Create(subject)
-                .RunGenerators(compilation);
+                .RunGeneratorsAndUpdateCompilation(compilation, out var outputCompilation, out _);
 
             var result = driver.GetRunResult();
 
@@ -2602,11 +2603,11 @@ private GeneratorDriverRunResult RunGenerator(Compilation compilation)
             }
             else
             {
-                _testOutputHelper.WriteLine($"Diagnostics produced:");
+                _testOutputHelper.WriteLine("Diagnostics produced:");
 
                 foreach (var diagnostic in result.Diagnostics)
                 {
-                    _testOutputHelper.WriteLine($" > " + diagnostic.ToString());
+                    _testOutputHelper.WriteLine(" > " + diagnostic);
                 }
             }
 
@@ -2616,7 +2617,30 @@ private GeneratorDriverRunResult RunGenerator(Compilation compilation)
                 _testOutputHelper.WriteLine(newSyntaxTree.GetText().ToString());
             }
 
-            return driver.GetRunResult();
+            // Verify that the generated code compiles without errors
+            var hasGeneratorErrors = result.Diagnostics.Any(d => d.Severity == DiagnosticSeverity.Error);
+            if (!hasGeneratorErrors && result.GeneratedTrees.Length > 0)
+            {
+                _testOutputHelper.WriteLine("Checking that generated code compiles...");
+
+                var compilationErrors = outputCompilation
+                    .GetDiagnostics()
+                    .Where(d => d.Severity == DiagnosticSeverity.Error)
+                    .ToList();
+
+                if (compilationErrors.Count > 0)
+                {
+                    _testOutputHelper.WriteLine("Generated code produced compilation errors:");
+                    foreach (var error in compilationErrors)
+                    {
+                        _testOutputHelper.WriteLine(" > " + error);
+                    }
+                }
+
+                Assert.Empty(compilationErrors);
+            }
+
+            return result;
         }
 
         #endregion