support for enum from/to string mapping in MapEnumValueAttribute

Added support for enum from/to string explicit mappings using MapEnumValueAttribute

---------

Co-authored-by: latonz <lars@riok.ch>

docs/docs/configuration/enum.mdx

@@ -59,7 +59,7 @@ The `IgnoreCase` property allows to opt in for case insensitive mappings (defaul
 ## Manually mapped enum values
 
 To explicitly map enum values the `MapEnumValueAttibute` can be used.
-Attribute is only valid on mapping methods with enums as parameters.
+Attribute is only valid on enum-to-enum, enum-to-string and string-to-enum mappings.
 
 ```csharp
 [Mapper]
@@ -70,6 +70,16 @@ public partial class CarMapper
     [MapEnumValue(CarFeature.AWD, CarFeatureDto.AllWheelDrive)]
     // highlight-end
     public partial CarFeatureDto MapFeature(CarFeature feature);
+
+    // highlight-start
+    [MapEnumValue("AWD", CarFeatureDto.AllWheelDrive)]
+    // highlight-end
+    public partial CarFeatureDto MapFeatureFromString(string feature);
+
+    // highlight-start
+    [MapEnumValue(CarFeatureDto.AllWheelDrive, "AWD")]
+    // highlight-end
+    public partial string MapFeatureToString(CarFeatureDto feature);
 }
 ```
 
@@ -80,7 +90,7 @@ This is especially useful when applying [strict enum mappings](#strict-enum-mapp
 
 ```csharp
 [Mapper]
-public partial class CarMapper
+public partial class FruitMapper
 {
     // highlight-start
     [MapperIgnoreSourceValue(Fruit.Apple)]

src/Riok.Mapperly.Abstractions/MapEnumValueAttribute.cs

@@ -12,21 +12,21 @@ public sealed class MapEnumValueAttribute : Attribute
     /// <summary>
     /// Customizes how enum values are mapped
     /// </summary>
-    /// <param name="source">The enum value to map from</param>
-    /// <param name="target">The enum value to map to</param>
+    /// <param name="source">The value to map from</param>
+    /// <param name="target">The value to map to</param>
     public MapEnumValueAttribute(object source, object target)
     {
-        Source = (Enum)source;
-        Target = (Enum)target;
+        Source = source;
+        Target = target;
     }
 
     /// <summary>
     /// What to map to
     /// </summary>
-    public Enum Target { get; }
+    public object Target { get; }
 
     /// <summary>
     /// What to map from
     /// </summary>
-    public Enum Source { get; }
+    public object Source { get; }
 }

src/Riok.Mapperly.Abstractions/PublicAPI.Shipped.txt

@@ -15,8 +15,6 @@ Riok.Mapperly.Abstractions.MapEnumAttribute.MapEnumAttribute(Riok.Mapperly.Abstr
 Riok.Mapperly.Abstractions.MapEnumAttribute.Strategy.get -> Riok.Mapperly.Abstractions.EnumMappingStrategy
 Riok.Mapperly.Abstractions.MapEnumValueAttribute
 Riok.Mapperly.Abstractions.MapEnumValueAttribute.MapEnumValueAttribute(object! source, object! target) -> void
-Riok.Mapperly.Abstractions.MapEnumValueAttribute.Source.get -> System.Enum!
-Riok.Mapperly.Abstractions.MapEnumValueAttribute.Target.get -> System.Enum!
 Riok.Mapperly.Abstractions.MapperAttribute
 Riok.Mapperly.Abstractions.MapperAttribute.EnabledConversions.get -> Riok.Mapperly.Abstractions.MappingConversionType
 Riok.Mapperly.Abstractions.MapperAttribute.EnabledConversions.set -> void
@@ -188,3 +186,5 @@ Riok.Mapperly.Abstractions.MapPropertyAttribute.MapPropertyAttribute(string! sou
 Riok.Mapperly.Abstractions.MapPropertyAttribute.MapPropertyAttribute(string![]! source, string! target) -> void
 Riok.Mapperly.Abstractions.MapperAttribute.IncludedConstructors.get -> Riok.Mapperly.Abstractions.MemberVisibility
 Riok.Mapperly.Abstractions.MapperAttribute.IncludedConstructors.set -> void
+Riok.Mapperly.Abstractions.MapEnumValueAttribute.Source.get -> object!
+Riok.Mapperly.Abstractions.MapEnumValueAttribute.Target.get -> object!

src/Riok.Mapperly/AnalyzerReleases.Shipped.md

@@ -186,6 +186,7 @@ RMG038  | Mapper   | Warning  | An enum member could not be found on the target
 RMG081  | Mapper   | Error    | A mapping method with additional parameters cannot be a default mapping
 RMG082  | Mapper   | Warning  | An additional mapping method parameter is not mapped
 RMG083  | Mapper   | Info     | Cannot map to read only type
+RMG084  | Mapper   | Error    | Multiple mappings are configured for the same source string
 
 ### Removed Rules
 
@@ -195,4 +196,3 @@ RMG017  | Mapper   | Warning  | An init only member can have one configuration a
 RMG026  | Mapper   | Info     | Cannot map from indexed member
 RMG027  | Mapper   | Warning  | A constructor parameter can have one configuration at max
 RMG028  | Mapper   | Warning  | Constructor parameter cannot handle target paths
-

src/Riok.Mapperly/Configuration/EnumValueMappingConfiguration.cs

@@ -1,4 +1,3 @@
-using Microsoft.CodeAnalysis;
 using Riok.Mapperly.Abstractions;
 
 namespace Riok.Mapperly.Configuration;
@@ -9,4 +8,4 @@ namespace Riok.Mapperly.Configuration;
 /// </summary>
 /// <param name="Source">The source constant of the enum value mapping.</param>
 /// <param name="Target">The target constant of the enum value mapping.</param>
-public record EnumValueMappingConfiguration(IFieldSymbol Source, IFieldSymbol Target);
+public record EnumValueMappingConfiguration(AttributeValue Source, AttributeValue Target);

src/Riok.Mapperly/Descriptors/MappingBodyBuilders/BuilderContext/EnumMappingDiagnosticReporter.cs

@@ -0,0 +1,88 @@
+using Microsoft.CodeAnalysis;
+using Riok.Mapperly.Abstractions;
+using Riok.Mapperly.Diagnostics;
+
+namespace Riok.Mapperly.Descriptors.MappingBodyBuilders.BuilderContext;
+
+internal static class EnumMappingDiagnosticReporter
+{
+    public static void AddUnmatchedSourceIgnoredMembers(MappingBuilderContext ctx, ISet<IFieldSymbol> ignoredSourceMembers)
+    {
+        var sourceFields = ctx.SymbolAccessor.GetAllFields(ctx.Source).ToHashSet();
+        var unmatchedSourceMembers = ignoredSourceMembers.Where(m => !sourceFields.Contains(m));
+
+        foreach (var member in unmatchedSourceMembers)
+        {
+            ctx.ReportDiagnostic(
+                DiagnosticDescriptors.IgnoredEnumSourceMemberNotFound,
+                member.Name,
+                member.ConstantValue!,
+                ctx.Source,
+                ctx.Target
+            );
+        }
+    }
+
+    public static void AddUnmatchedTargetIgnoredMembers(MappingBuilderContext ctx, ISet<IFieldSymbol> ignoredTargetMembers)
+    {
+        var targetFields = ctx.SymbolAccessor.GetAllFields(ctx.Target).ToHashSet();
+        var unmatchedTargetMembers = ignoredTargetMembers.Where(m => !targetFields.Contains(m));
+
+        foreach (var member in unmatchedTargetMembers)
+        {
+            ctx.ReportDiagnostic(
+                DiagnosticDescriptors.IgnoredEnumTargetMemberNotFound,
+                member.Name,
+                member.ConstantValue!,
+                ctx.Source,
+                ctx.Target
+            );
+        }
+    }
+
+    public static void AddUnmappedTargetMembersDiagnostics(
+        MappingBuilderContext ctx,
+        ISet<IFieldSymbol> mappings,
+        IEnumerable<IFieldSymbol> targetMembers
+    )
+    {
+        if (!ctx.Configuration.Enum.RequiredMappingStrategy.HasFlag(RequiredMappingStrategy.Target))
+            return;
+
+        var missingTargetMembers = targetMembers.Where(field =>
+            !mappings.Contains(field) && ctx.Configuration.Enum.FallbackValue?.ConstantValue?.Equals(field.ConstantValue) != true
+        );
+        foreach (var member in missingTargetMembers)
+        {
+            ctx.ReportDiagnostic(
+                DiagnosticDescriptors.TargetEnumValueNotMapped,
+                member.Name,
+                member.ConstantValue!,
+                ctx.Target,
+                ctx.Source
+            );
+        }
+    }
+
+    public static void AddUnmappedSourceMembersDiagnostics(
+        MappingBuilderContext ctx,
+        ISet<IFieldSymbol> mappings,
+        IEnumerable<IFieldSymbol> sourceMembers
+    )
+    {
+        if (!ctx.Configuration.Enum.RequiredMappingStrategy.HasFlag(RequiredMappingStrategy.Source))
+            return;
+
+        var missingSourceMembers = sourceMembers.Where(field => !mappings.Contains(field));
+        foreach (var member in missingSourceMembers)
+        {
+            ctx.ReportDiagnostic(
+                DiagnosticDescriptors.SourceEnumValueNotMapped,
+                member.Name,
+                member.ConstantValue!,
+                ctx.Source,
+                ctx.Target
+            );
+        }
+    }
+}