From 180bf22b0bc474bd2bff61c83f976e1820ca2dcd Mon Sep 17 00:00:00 2001
From: Mohammadreza Taikandi <mrtaikandi@hotmail.com>
Date: Sat, 3 Jul 2021 07:22:54 +0100
Subject: [PATCH] Fix namespace conflict if part of it shared by the system
 namespace.

---
 src/MapTo/Sources/MapClassSource.cs    |  4 +--
 src/MapTo/Sources/MapRecordSource.cs   |  4 +--
 test/MapTo.Tests/MapToTests.cs         | 37 +++++++++++++-------------
 test/MapTo.Tests/MappedClassesTests.cs | 32 ++++++++++++++++++++++
 4 files changed, 55 insertions(+), 22 deletions(-)

diff --git a/src/MapTo/Sources/MapClassSource.cs b/src/MapTo/Sources/MapClassSource.cs
index 803006a..edde823 100644
--- a/src/MapTo/Sources/MapClassSource.cs
+++ b/src/MapTo/Sources/MapClassSource.cs
@@ -10,12 +10,12 @@ namespace MapTo.Sources
             using var builder = new SourceBuilder()
                 .WriteLine(GeneratedFilesHeader)
                 .WriteNullableContextOptionIf(model.Options.SupportNullableReferenceTypes)
+                .WriteUsings(model.Usings)
+                .WriteLine()
 
                 // Namespace declaration
                 .WriteLine($"namespace {model.Namespace}")
                 .WriteOpeningBracket()
-                .WriteUsings(model.Usings)
-                .WriteLine()
 
                 // Class declaration
                 .WriteLine($"partial class {model.TypeIdentifierName}")
diff --git a/src/MapTo/Sources/MapRecordSource.cs b/src/MapTo/Sources/MapRecordSource.cs
index 9614ab1..c2988c0 100644
--- a/src/MapTo/Sources/MapRecordSource.cs
+++ b/src/MapTo/Sources/MapRecordSource.cs
@@ -11,12 +11,12 @@ namespace MapTo.Sources
             using var builder = new SourceBuilder()
                 .WriteLine(GeneratedFilesHeader)
                 .WriteNullableContextOptionIf(model.Options.SupportNullableReferenceTypes)
+                .WriteUsings(model.Usings)
+                .WriteLine()
 
                 // Namespace declaration
                 .WriteLine($"namespace {model.Namespace}")
                 .WriteOpeningBracket()
-                .WriteUsings(model.Usings)
-                .WriteLine()
 
                 // Class declaration
                 .WriteLine($"partial record {model.TypeIdentifierName}")
diff --git a/test/MapTo.Tests/MapToTests.cs b/test/MapTo.Tests/MapToTests.cs
index a919de3..e09009c 100644
--- a/test/MapTo.Tests/MapToTests.cs
+++ b/test/MapTo.Tests/MapToTests.cs
@@ -122,11 +122,11 @@ namespace Test
 
             const string expectedResult = @"
 // <auto-generated />
+using MapTo;
+using System;
+
 namespace Test
 {
-    using MapTo;
-    using System;
-
     partial class Foo
     {
         public Foo(Test.Baz baz)
@@ -198,11 +198,11 @@ namespace Test
 
             const string expectedResult = @"
 // <auto-generated />
+using MapTo;
+using System;
+
 namespace Test
 {
-    using MapTo;
-    using System;
-
     partial class Foo
     {
         public Foo(Test.Baz baz)
@@ -260,10 +260,11 @@ namespace Test
 
             const string expectedResult = @"
 // <auto-generated />
+using MapTo;
+using System;
+
 namespace Test
 {
-    using MapTo;
-    using System;
 ";
 
             // Act
@@ -526,13 +527,13 @@ private protected ManagerViewModel(MappingContext context, Test.Data.Models.Mana
 
             const string expectedResult = @"
 // <auto-generated />
+using MapTo;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
 namespace Test.ViewModels
 {
-    using MapTo;
-    using System;
-    using System.Collections.Generic;
-    using System.Linq;
-
     partial class ManagerViewModel
     {
         public ManagerViewModel(Test.Data.Models.Manager manager)
@@ -565,13 +566,13 @@ namespace Test.ViewModels
             var sources = GetEmployeeManagerSourceText(useDifferentViewModelNamespace: true);
 
             const string expectedResult = @"
+using MapTo;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
 namespace Test.ViewModels2
 {
-    using MapTo;
-    using System;
-    using System.Collections.Generic;
-    using System.Linq;
-
     partial class ManagerViewModel
     {
         public ManagerViewModel(Test.Data.Models.Manager manager)
diff --git a/test/MapTo.Tests/MappedClassesTests.cs b/test/MapTo.Tests/MappedClassesTests.cs
index e9d463d..009c440 100644
--- a/test/MapTo.Tests/MappedClassesTests.cs
+++ b/test/MapTo.Tests/MappedClassesTests.cs
@@ -407,6 +407,38 @@ namespace Tests.Data.ViewModels
             _output.WriteLine(compilation.PrintSyntaxTree());
         }
 
+        [Fact]
+        public void VerifySystemNamespaceConflict()
+        {
+            // Arrange
+            var source = @"
+namespace Test
+{
+    public record SomeRecord(int Id);
+}
+
+namespace Test.Models
+{
+    using MapTo;
+
+    [MapFrom(typeof(Test.SomeRecord))]
+    public partial record SomeRecordModel(int Id);
+}
+
+namespace Test.System
+{
+    public interface IMyInterface { }
+}
+".Trim();
+
+            // Act
+            var (compilation, diagnostics) = CSharpGenerator.GetOutputCompilation(source, analyzerConfigOptions: DefaultAnalyzerOptions, languageVersion: LanguageVersion.CSharp9);
+
+            // Assert
+            diagnostics.ShouldBeSuccessful();
+            _output.WriteLine(compilation.PrintSyntaxTree());
+        }
+
         private static string MainSourceClass => @"
 using System;