feat: add EnsureCapacity to dctionary foreach loops (#361)

src/Riok.Mapperly/Descriptors/Enumerables/EnsureCapacity/EnsureCapacityBuilder.cs

@@ -42,6 +42,10 @@ public static class EnsureCapacityBuilder
                 x => x.ReturnType.SpecialType == SpecialType.System_Boolean && x.IsStatic && x.Parameters.Length == 2 && x.IsGenericMethod
             );
 
+        // if non enumerated method doesnt exist then don't create EnsureCapacity
+        if (nonEnumeratedCountMethod == null)
+            return null;
+
         // if source does not have a count use GetNonEnumeratedCount, calling EnusureCapacity if count is available
         var typedNonEnumeratedCount = nonEnumeratedCountMethod.Construct(iEnumerable!.TypeArguments.ToArray());
         return new EnsureCapacityNonEnumerated(targetSizeProperty, typedNonEnumeratedCount);

src/Riok.Mapperly/Descriptors/MappingBuilders/DictionaryMappingBuilder.cs

@@ -1,6 +1,7 @@
 using System.Collections.Immutable;
 using Microsoft.CodeAnalysis;
 using Riok.Mapperly.Abstractions;
+using Riok.Mapperly.Descriptors.Enumerables.EnsureCapacity;
 using Riok.Mapperly.Descriptors.Mappings;
 using Riok.Mapperly.Descriptors.Mappings.ExistingTarget;
 using Riok.Mapperly.Diagnostics;
@@ -64,14 +65,17 @@ public static class DictionaryMappingBuilder
         if (!ctx.Target.ImplementsGeneric(ctx.Types.IDictionaryT, out _))
             return null;
 
+        var ensureCapacityStatement = EnsureCapacityBuilder.TryBuildEnsureCapacity(ctx.Source, ctx.Target, ctx.Types);
+
         return new ForEachSetDictionaryMapping(
             ctx.Source,
             ctx.Target,
             keyMapping,
             valueMapping,
             false,
             objectFactory: objectFactory,
-            explicitCast: GetExplicitIndexer(ctx)
+            explicitCast: GetExplicitIndexer(ctx),
+            ensureCapacity: ensureCapacityStatement
         );
     }
 
@@ -91,12 +95,15 @@ public static class DictionaryMappingBuilder
         }
 
         // add values to dictionary by setting key values in a foreach loop
+        var ensureCapacityStatement = EnsureCapacityBuilder.TryBuildEnsureCapacity(ctx.Source, ctx.Target, ctx.Types);
+
         return new ForEachSetDictionaryExistingTargetMapping(
             ctx.Source,
             ctx.Target,
             keyMapping,
             valueMapping,
-            explicitCast: GetExplicitIndexer(ctx)
+            explicitCast: GetExplicitIndexer(ctx),
+            ensureCapacity: ensureCapacityStatement
         );
     }
 

src/Riok.Mapperly/Descriptors/Mappings/ExistingTarget/ForEachSetDictionaryExistingTargetMapping.cs

@@ -1,5 +1,6 @@
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Riok.Mapperly.Descriptors.Enumerables.EnsureCapacity;
 using static Microsoft.CodeAnalysis.CSharp.SyntaxFactory;
 using static Riok.Mapperly.Emit.SyntaxFactoryHelper;
 
@@ -19,19 +20,22 @@ public class ForEachSetDictionaryExistingTargetMapping : ExistingTargetMapping
     private readonly ITypeMapping _keyMapping;
     private readonly ITypeMapping _valueMapping;
     private readonly INamedTypeSymbol? _explicitCast;
+    private readonly EnsureCapacity? _ensureCapacity;
 
     public ForEachSetDictionaryExistingTargetMapping(
         ITypeSymbol sourceType,
         ITypeSymbol targetType,
         ITypeMapping keyMapping,
         ITypeMapping valueMapping,
-        INamedTypeSymbol? explicitCast
+        INamedTypeSymbol? explicitCast,
+        EnsureCapacity? ensureCapacity
     )
         : base(sourceType, targetType)
     {
         _keyMapping = keyMapping;
         _valueMapping = valueMapping;
         _explicitCast = explicitCast;
+        _ensureCapacity = ensureCapacity;
     }
 
     public override IEnumerable<StatementSyntax> Build(TypeMappingBuildContext ctx, ExpressionSyntax target)
@@ -47,6 +51,11 @@ public override IEnumerable<StatementSyntax> Build(TypeMappingBuildContext ctx,
             yield return LocalDeclarationStatement(DeclareVariable(castedVariable, cast));
         }
 
+        if (_ensureCapacity != null)
+        {
+            yield return _ensureCapacity.Build(ctx, target);
+        }
+
         var loopItemVariableName = ctx.NameBuilder.New(LoopItemVariableName);
 
         var convertedKeyExpression = _keyMapping.Build(ctx.WithSource(MemberAccess(loopItemVariableName, KeyPropertyName)));

src/Riok.Mapperly/Descriptors/Mappings/ForEachSetDictionaryMapping.cs

@@ -1,5 +1,6 @@
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Riok.Mapperly.Descriptors.Enumerables.EnsureCapacity;
 using Riok.Mapperly.Descriptors.Mappings.ExistingTarget;
 using Riok.Mapperly.Descriptors.ObjectFactories;
 using static Riok.Mapperly.Emit.SyntaxFactoryHelper;
@@ -26,9 +27,12 @@ public ForEachSetDictionaryMapping(
         bool sourceHasCount,
         ITypeSymbol? typeToInstantiate = null,
         ObjectFactory? objectFactory = null,
-        INamedTypeSymbol? explicitCast = null
+        INamedTypeSymbol? explicitCast = null,
+        EnsureCapacity? ensureCapacity = null
     )
-        : base(new ForEachSetDictionaryExistingTargetMapping(sourceType, targetType, keyMapping, valueMapping, explicitCast))
+        : base(
+            new ForEachSetDictionaryExistingTargetMapping(sourceType, targetType, keyMapping, valueMapping, explicitCast, ensureCapacity)
+        )
     {
         _sourceHasCount = sourceHasCount;
         _objectFactory = objectFactory;

src/Riok.Mapperly/Helpers/SymbolExtensions.cs

@@ -116,6 +116,12 @@ out bool isExplicit
             return false;
         }
 
+        if (t.IsAbstract)
+        {
+            isExplicit = false;
+            return true;
+        }
+
         var interfaceSymbol = typedInterface.GetMembers(symbolName).First();
 
         var symbolImplementaton = t.FindImplementationForInterfaceMember(interfaceSymbol);

test/Riok.Mapperly.Tests/Mapping/DictionaryTest.cs

@@ -194,6 +194,7 @@ public void DictionaryToCustomDictionary()
             .HaveSingleMethodBody(
                 """
                 var target = new global::A();
+                target.EnsureCapacity(source.Count + target.Count);
                 foreach (var item in source)
                 {
                     target[item.Key] = item.Value;
@@ -217,6 +218,7 @@ public void DictionaryToCustomDictionaryWithObjectFactory()
             .HaveSingleMethodBody(
                 """
                 var target = CreateA();
+                target.EnsureCapacity(source.Count + target.Count);
                 foreach (var item in source)
                 {
                     target[item.Key] = item.Value;
@@ -227,6 +229,71 @@ public void DictionaryToCustomDictionaryWithObjectFactory()
             );
     }
 
+    [Fact]
+    public void MapToExistingDictionary()
+    {
+        var source = TestSourceBuilder.MapperWithBodyAndTypes(
+            "partial void Map(IDictionary<string, int> source, Dictionary<string, int> target);"
+        );
+        TestHelper
+            .GenerateMapper(source)
+            .Should()
+            .HaveSingleMethodBody(
+                """
+                target.EnsureCapacity(source.Count + target.Count);
+                foreach (var item in source)
+                {
+                    target[item.Key] = item.Value;
+                }
+                """
+            );
+    }
+
+    [Fact]
+    public void MapToExistingCustomDictionary()
+    {
+        var source = TestSourceBuilder.MapperWithBodyAndTypes(
+            "partial void Map(IDictionary<string, int> source, A target);",
+            "class A : Dictionary<string, int> {}"
+        );
+        TestHelper
+            .GenerateMapper(source)
+            .Should()
+            .HaveSingleMethodBody(
+                """
+                target.EnsureCapacity(source.Count + target.Count);
+                foreach (var item in source)
+                {
+                    target[item.Key] = item.Value;
+                }
+                """
+            );
+    }
+
+    [Fact]
+    public void KeyValueEnumerableToExistingDictionary()
+    {
+        var source = TestSourceBuilder.MapperWithBodyAndTypes(
+            "partial void Map(IEnumerable<KeyValuePair<string, int>> source, Dictionary<string, int> target);"
+        );
+        TestHelper
+            .GenerateMapper(source)
+            .Should()
+            .HaveSingleMethodBody(
+                """
+                if (global::System.Linq.Enumerable.TryGetNonEnumeratedCount(source, out var sourceCount))
+                {
+                    target.EnsureCapacity(sourceCount + target.Count);
+                }
+
+                foreach (var item in source)
+                {
+                    target[item.Key] = item.Value;
+                }
+                """
+            );
+    }
+
     [Fact]
     public void IDictionaryToExplicitDictionaryShouldCast()
     {