Add attribute to exclude a property from mapping.

src/MapTo/MapToGenerator.cs

@@ -20,8 +20,9 @@ namespace MapTo
         /// <inheritdoc />
         public void Execute(GeneratorExecutionContext context)
         {
-            AddMapFromAttribute(context);
+            AddAttribute(context, SourceBuilder.GenerateMapFromAttribute());
-
+            AddAttribute(context, SourceBuilder.GenerateIgnorePropertyAttribute());
+            
             if (context.SyntaxReceiver is MapToSyntaxReceiver receiver && receiver.CandidateClasses.Any())
             {
                 AddGeneratedMappingsClasses(context, receiver.CandidateClasses);
@@ -44,11 +45,8 @@ namespace MapTo
             }
         }
 
-        private static void AddMapFromAttribute(GeneratorExecutionContext context)
+        private static void AddAttribute(GeneratorExecutionContext context, (string source, string hintName) attribute) 
-        {
+            => context.AddSource(attribute.hintName, attribute.source);
-            var (source, hintName) = SourceBuilder.GenerateMapFromAttribute();
-            context.AddSource(hintName, source);
-        }
 
         private static INamedTypeSymbol? GetSourceTypeSymbol(ClassDeclarationSyntax classSyntax, SemanticModel model)
         {
@@ -104,7 +102,10 @@ namespace MapTo
             return sourceTypeSymbol
                 .GetAllMembersOfType<IPropertySymbol>()
                 .Select(p => p.Name)
-                .Intersect(classSymbol.GetAllMembersOfType<IPropertySymbol>().Select(p => p.Name))
+                .Intersect(classSymbol
+                    .GetAllMembersOfType<IPropertySymbol>()
+                    .Where(p => p.GetAttributes().All(a => a.AttributeClass?.Name != SourceBuilder.IgnorePropertyAttributeName))
+                    .Select(p => p.Name))
                 .ToImmutableArray();
         }
     }

src/MapTo/SourceBuilder.cs

@@ -1,10 +1,7 @@
-using System;
+using System.Linq;
-using System.Collections.Generic;
-using System.Linq;
 using System.Text;
 using MapTo.Extensions;
 using MapTo.Models;
-using Microsoft.CodeAnalysis;
 
 namespace MapTo
 {
@@ -12,33 +9,49 @@ namespace MapTo
     {
         internal const string NamespaceName = "MapTo";
         internal const string MapFromAttributeName = "MapFrom";
-        private const int Indent1 = 4; //"    ";
+        internal const string IgnorePropertyAttributeName = "IgnoreProperty";
-        private const int Indent2 = Indent1 * 2; // "        ";
+        internal const string GeneratedFilesHeader = "// <auto-generated />";
-        private const int Indent3 = Indent1 * 3; // "            ";
+        
+        private const int Indent1 = 4;
+        private const int Indent2 = Indent1 * 2;
+        private const int Indent3 = Indent1 * 3;
 
         internal static (string source, string hintName) GenerateMapFromAttribute()
         {
-            const string source = @"
+            var source = $@"{GeneratedFilesHeader}
 using System;
 
 namespace MapTo
-{
+{{
     [AttributeUsage(AttributeTargets.Class, Inherited = false, AllowMultiple = false)]
-    public sealed class MapFromAttribute : Attribute
+    public sealed class {MapFromAttributeName}Attribute : Attribute
-    {
+    {{
-        public MapFromAttribute(Type sourceType)
+        public {MapFromAttributeName}Attribute(Type sourceType)
-        {
+        {{
             SourceType = sourceType;
-        }
+        }}
 
-        public Type SourceType { get; }
+        public Type SourceType {{ get; }}
-    }
+    }}
-}
+}}";
-";
 
             return (source, $"{MapFromAttributeName}Attribute.g.cs");
         }
 
+        internal static (string source, string hintName) GenerateIgnorePropertyAttribute()
+        {
+            var source = $@"{GeneratedFilesHeader}
+using System;
+
+namespace MapTo
+{{
+    [AttributeUsage(AttributeTargets.Property, Inherited = false, AllowMultiple = false)]
+    public sealed class {IgnorePropertyAttributeName}Attribute : Attribute {{ }}
+}}";
+
+            return (source, $"{IgnorePropertyAttributeName}Attribute.g.cs");
+        }
+
         internal static (string source, string hintName) GenerateSource(MapModel model)
         {
             var builder = new StringBuilder();
@@ -141,7 +154,6 @@ namespace MapTo
         }
 
         private static StringBuilder AppendFileHeader(this StringBuilder builder) =>
-            builder
+            builder.AppendLine(GeneratedFilesHeader);
-                .AppendLine("// <auto-generated />");
     }
 }

test/MapTo.Tests/CompilerServices/IsExternalInit.cs

@@ -0,0 +1,16 @@
+// ReSharper disable UnusedType.Global
+// ReSharper disable CheckNamespace
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.ComponentModel;
+
+namespace System.Runtime.CompilerServices
+{
+    /// <summary>
+    /// Reserved to be used by the compiler for tracking metadata.
+    /// This class should not be used by developers in source code.
+    /// </summary>
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    internal static class IsExternalInit { }
+}

test/MapTo.Tests/Tests.cs

@@ -1,5 +1,7 @@
+using System;
 using System.Linq;
 using System.Text;
+using MapTo.Extensions;
 using MapToTests;
 using Microsoft.CodeAnalysis;
 using Shouldly;
@@ -10,6 +12,10 @@ namespace MapTo.Tests
 {
     public class Tests
     {
+        private const int Indent1 = 4;
+        private const int Indent2 = Indent1 * 2;
+        private const int Indent3 = Indent1 * 3;
+        
         public Tests(ITestOutputHelper output)
         {
             _output = output;
@@ -17,54 +23,100 @@ namespace MapTo.Tests
 
         private readonly ITestOutputHelper _output;
 
-        private const string ExpectedAttribute = @"
+        private static readonly string ExpectedAttribute = $@"{SourceBuilder.GeneratedFilesHeader}
 using System;
 
 namespace MapTo
-{
+{{
     [AttributeUsage(AttributeTargets.Class, Inherited = false, AllowMultiple = false)]
     public sealed class MapFromAttribute : Attribute
-    {
+    {{
         public MapFromAttribute(Type sourceType)
-        {
+        {{
             SourceType = sourceType;
-        }
+        }}
 
-        public Type SourceType { get; }
+        public Type SourceType {{ get; }}
-    }
+    }}
-}
+}}";
-";
 
-        private static string GetSourceText(bool includeAttributeNamespace = false, string sourceClassNamespace = "Test.Models")
+        private record SourceGeneratorOptions(
+            bool UseMapToNamespace = false, 
+            string SourceClassNamespace = "Test.Models", 
+            int ClassPropertiesCount = 3, 
+            int SourceClassPropertiesCount = 3,
+            Action<StringBuilder> PropertyBuilder = null,
+            Action<StringBuilder> SourcePropertyBuilder = null);
+        
+        private static string GetSourceText(SourceGeneratorOptions options = null)
         {
+            const string ns = "Test";
+            options ??= new SourceGeneratorOptions();
+            var hasDifferentSourceNamespace = options.SourceClassNamespace != ns;
             var builder = new StringBuilder();
-            builder.AppendLine($@"
+            
-{(includeAttributeNamespace ? string.Empty : "using MapTo;")}
+            if (options.UseMapToNamespace)
-namespace Test
+            {
-{{
+                builder.AppendFormat("using {0};", SourceBuilder.NamespaceName).AppendLine();
-    {(sourceClassNamespace != "Test" && !includeAttributeNamespace ? $"using {sourceClassNamespace};" : string.Empty)}
+            }
 
-    {(includeAttributeNamespace ? "[MapTo.MapFrom(typeof(Baz))]" : "[MapFrom(typeof(Baz))]")}
+            builder
-    public partial class Foo
+                .AppendFormat("using {0};", options.SourceClassNamespace)
-    {{
+                .AppendLine()
-        public int Prop1 {{ get; set; }}
+                .AppendLine();
-        public int Prop2 {{ get; }}
-        public int Prop3 {{ get; }}
-    }}
-}}
-");
 
-            builder.AppendLine($@"
+            builder
-namespace {sourceClassNamespace}
+                .AppendFormat("namespace {0}", ns)
-{{
+                .AppendOpeningBracket();
-    public class Baz 
+
-    {{
+            if (hasDifferentSourceNamespace && options.UseMapToNamespace)
-        public int Prop1 {{ get; set; }}
+            {
-        public int Prop2 {{ get;  }}
+                builder
-        public int Prop3 {{ get; set; }}
+                    .PadLeft(Indent1)
-    }}
+                    .AppendFormat("using {0};", options.SourceClassNamespace)
-}}
+                    .AppendLine()
-");
+                    .AppendLine();
+            }
+            
+            builder
+                .PadLeft(Indent1)
+                .AppendLine(options.UseMapToNamespace ? "[MapTo.MapFrom(typeof(Baz))]" : "[MapFrom(typeof(Baz))]")
+                .PadLeft(Indent1).Append("public partial class Foo")
+                .AppendOpeningBracket(Indent1);
+
+            for (var i = 1; i <= options.ClassPropertiesCount; i++)
+            {
+                builder
+                    .PadLeft(Indent2)
+                    .AppendLine(i % 2 == 0 ? $"public int Prop{i} {{ get; set; }}" : $"public int Prop{i} {{ get; }}");
+            }
+            
+            options.PropertyBuilder?.Invoke(builder);
+
+            builder
+                .AppendClosingBracket(Indent1, padNewLine: false)
+                .AppendClosingBracket()
+                .AppendLine()
+                .AppendLine();
+            
+            builder
+                .AppendFormat("namespace {0}", options.SourceClassNamespace)
+                .AppendOpeningBracket()
+                .PadLeft(Indent1).Append("public class Baz")
+                .AppendOpeningBracket(Indent1);
+
+            for (var i = 1; i <= options.SourceClassPropertiesCount; i++)
+            {
+                builder
+                    .PadLeft(Indent2)
+                    .AppendLine(i % 2 == 0 ? $"public int Prop{i} {{ get; set; }}" : $"public int Prop{i} {{ get; }}");
+            }
+            
+            options.SourcePropertyBuilder?.Invoke(builder);
+            
+            builder
+                .AppendClosingBracket(Indent1, padNewLine: false)
+                .AppendClosingBracket();
 
             return builder.ToString();
         }
@@ -126,7 +178,6 @@ namespace Test
 
             // Assert
             diagnostics.ShouldBeSuccessful();
-            compilation.SyntaxTrees.Count().ShouldBe(3);
             compilation.SyntaxTrees.Last().ToString().ShouldStartWith(expectedResult.Trim());
         }
         
@@ -190,7 +241,6 @@ namespace Test
 
             // Assert
             diagnostics.ShouldBeSuccessful();
-            compilation.SyntaxTrees.Count().ShouldBe(3);
             compilation.SyntaxTrees.Last().ToString().ShouldStartWith(expectedResult.Trim());
         }
 
@@ -205,15 +255,18 @@ namespace Test
 
             // Assert
             diagnostics.ShouldBeSuccessful();
-            compilation.SyntaxTrees.ShouldContain(s => s.ToString() == ExpectedAttribute);
+            compilation.SyntaxTrees
-            compilation.SyntaxTrees.Select(s => s.ToString()).Where(s => s != string.Empty && s != ExpectedAttribute).ShouldBeEmpty();
+                .Select(s => s.ToString())
+                .Where(s => !string.IsNullOrWhiteSpace(s.ToString()))
+                .All(s => s.Contains(": Attribute"))
+                .ShouldBeTrue();
         }
 
         [Fact]
         public void When_SourceTypeHasDifferentNamespace_Should_NotAddToUsings()
         {
             // Arrange
-            var source = GetSourceText(sourceClassNamespace: "Bazaar");
+            var source = GetSourceText(new SourceGeneratorOptions(SourceClassNamespace: "Bazaar"));
 
             const string expectedResult = @"
 // <auto-generated />
@@ -227,7 +280,6 @@ namespace Test
 
             // Assert
             diagnostics.ShouldBeSuccessful();
-            compilation.SyntaxTrees.Count().ShouldBe(3);
             compilation.SyntaxTrees.Last().ToString().ShouldStartWith(expectedResult.Trim());
         }
 
@@ -255,7 +307,6 @@ namespace Test
 
             // Assert
             diagnostics.ShouldBeSuccessful();
-            compilation.SyntaxTrees.Count().ShouldBe(3);
             compilation.SyntaxTrees.Last().ToString().ShouldContain(expectedResult.Trim());
         }
 
@@ -277,7 +328,6 @@ namespace Test
 
             // Assert
             diagnostics.ShouldBeSuccessful();
-            compilation.SyntaxTrees.Count().ShouldBe(3);
             compilation.SyntaxTrees.Last().ToString().ShouldContain(expectedResult.Trim());
         }
 
@@ -302,8 +352,66 @@ namespace Test
 
             // Assert
             diagnostics.ShouldBeSuccessful();
-            compilation.SyntaxTrees.Count().ShouldBe(3);
             compilation.SyntaxTrees.Last().ToString().ShouldContain(expectedResult.Trim());
         }
+        
+        [Fact]
+        public void VerifyIgnorePropertyAttribute()
+        {
+            // Arrange
+            const string source = "";
+            var expectedAttribute = $@"
+{SourceBuilder.GeneratedFilesHeader}
+using System;
+
+namespace MapTo
+{{
+    [AttributeUsage(AttributeTargets.Property, Inherited = false, AllowMultiple = false)]
+    public sealed class IgnorePropertyAttribute : Attribute {{ }}
+}}
+".Trim();
+
+            // Act
+            var (compilation, diagnostics) = CSharpGenerator.GetOutputCompilation(source);
+
+            // Assert
+            diagnostics.ShouldBeSuccessful();
+            compilation.SyntaxTrees.ShouldContain(c => c.ToString() == expectedAttribute);
+        }
+
+        [Fact]
+        public void When_IgnorePropertyAttributeIsSpecified_Should_NotGenerateMappingsForThatProperty()
+        {
+            // Arrange
+            var source = GetSourceText(new SourceGeneratorOptions(
+                UseMapToNamespace: true,
+                PropertyBuilder: builder =>
+                {
+                    builder
+                        .PadLeft(Indent2).AppendLine("[IgnoreProperty]")
+                        .PadLeft(Indent2).AppendLine("public int Prop4 { get; set; }");
+                },
+                SourcePropertyBuilder: builder => builder.PadLeft(Indent2).AppendLine("public int Prop4 { get; set; }")));
+
+            var expectedResult = @"
+    public partial class Foo
+    {
+        public Foo(Test.Models.Baz baz)
+        {
+            if (baz == null) throw new ArgumentNullException(nameof(baz));
+
+            Prop1 = baz.Prop1;
+            Prop2 = baz.Prop2;
+            Prop3 = baz.Prop3;
+        }
+".Trim();
+            
+            // Act
+            var (compilation, diagnostics) = CSharpGenerator.GetOutputCompilation(source);
+
+            // Assert
+            diagnostics.ShouldBeSuccessful();
+            compilation.SyntaxTrees.Last().ToString().ShouldContain(expectedResult);
+        }
     }
 }

test/TestConsoleApp/ViewModels/UserViewModel.cs

@@ -7,6 +7,7 @@ namespace TestConsoleApp.ViewModels
     {
         public string FirstName { get; }
 
+        // [IgnoreProerty]
         public string LastName { get; }
     }
 }