Added UnmappedPropertiesAttribute to declare multiple unmapped properties at once.

Author: oliverhanappi

src/Analyzers/MappingAnalyzer.cs

@@ -59,6 +59,10 @@ private void OnMethodDeclaration(SyntaxNodeAnalysisContext context)
         .Select(a => (string) a.ConstructorArguments[0].Value)
         .ToList();
 
+      excludedPropertyNames.AddRange(method.GetAttributes()
+        .Where(a => a.AttributeClass.Name == "UnmappedPropertiesAttribute")
+        .SelectMany(a => a.ConstructorArguments[0].Values.Select(v => (string) v.Value)));
+
       var unmappedPropertyNames = mappingTargetProperties
         .Except(mappedProperties, new RootPropertyEqualityComparer())
         .Select(p => p.Name)

src/Core/UnmappedPropertiesAttribute.cs

@@ -0,0 +1,16 @@
+using System;
+using System.Collections.Generic;
+
+namespace ManualMappingGuard
+{
+  [AttributeUsage(AttributeTargets.Method, AllowMultiple = true)]
+  public class UnmappedPropertiesAttribute : Attribute
+  {
+    public IReadOnlyCollection<string> PropertyNames { get; }
+
+    public UnmappedPropertiesAttribute(params string[] propertyNames)
+    {
+      PropertyNames = propertyNames ?? throw new ArgumentNullException(nameof(propertyNames));
+    }
+  }
+}

src/Tests/Analyzers/MappingAnalyzerTests.cs

@@ -138,7 +138,7 @@ public Person Map()
     }
 
     [Test]
-    public async Task UnmappedProperty_Excluded_DoesNotReportMissingProperty()
+    public async Task UnmappedProperty_ExcludedSingle_DoesNotReportMissingProperty()
     {
       var diagnostics = await Analyze(@"
         public class Person
@@ -157,7 +157,26 @@ public class Person
     }
 
     [Test]
-    public async Task UnmappedProperty_MultipleExcluded_DoesNotReportMissingProperties()
+    public async Task UnmappedProperty_ExcludedMultiple_DoesNotReportMissingProperty()
+    {
+      var diagnostics = await Analyze(@"
+        public class Person
+        {
+          public int Id { get; set; }
+          public string FirstName { get; set; }
+          public string LastName { get; set; }
+        }
+
+        [MappingMethod]
+        [UnmappedProperties(nameof(Person.Id))]
+        public Person Map() => new Person { FirstName = ""Test"" };
+      ");
+
+      AssertUnmappedProperties(diagnostics, "LastName");
+    }
+
+    [Test]
+    public async Task UnmappedProperty_MultipleExcludedIndividually_DoesNotReportMissingProperties()
     {
       var diagnostics = await Analyze(@"
         public class Person
@@ -179,7 +198,28 @@ public class Person
     }
 
     [Test]
-    public async Task NonExistingExcludedProperty_DoesNotFail()
+    public async Task UnmappedProperty_MultipleExcludedAtOnce_DoesNotReportMissingProperties()
+    {
+      var diagnostics = await Analyze(@"
+        public class Person
+        {
+          public const string IdPropertyName = ""Id"";
+
+          public int Id { get; set; }
+          public string FirstName { get; set; }
+          public string LastName { get; set; }
+        }
+
+        [MappingMethod]
+        [UnmappedProperties(Person.IdPropertyName, ""LastName"")]
+        public Person Map() => new Person { FirstName = ""Test"" };
+      ");
+
+      AssertNoUnmappedProperties(diagnostics);
+    }
+
+    [Test]
+    public async Task NonExistingExcludedProperty_Single_DoesNotFail()
     {
       var diagnostics = await Analyze(@"
         public class Person { }
@@ -192,6 +232,20 @@ public class Person { }
       Assert.That(diagnostics, Is.Empty);
     }
 
+    [Test]
+    public async Task NonExistingExcludedProperty_Multiple_DoesNotFail()
+    {
+      var diagnostics = await Analyze(@"
+        public class Person { }
+
+        [MappingMethod]
+        [UnmappedProperties(""NotExisting1"", ""NonExisting2"")]
+        public Person Map() => new Person();
+      ");
+
+      Assert.That(diagnostics, Is.Empty);
+    }
+
     private void AssertMissingMappingTargetType(ImmutableArray<Diagnostic> diagnostics)
     {
       var expectedMessages = new[]

src/Tests/Core/UnmappedPropertiesAttributeTests.cs

@@ -0,0 +1,14 @@
+using NUnit.Framework;
+
+namespace ManualMappingGuard.Core
+{
+  [TestFixture]
+  public class UnmappedPropertiesAttributeTests
+  {
+    [Test]
+    public void NullPropertyNames_ThrowsException()
+    {
+      Assert.That(() => new UnmappedPropertiesAttribute((string[]) null!), Throws.ArgumentNullException);
+    }
+  }
+}