Adds expression support for filtering

src/HotChocolate/Data/src/Data/DataResources.resx

@@ -245,6 +245,12 @@
   <data name="QueryableFiltering_MemberInvalid" xml:space="preserve">
     <value>Filtering needs a member of type PropertyInfo or MethodInfo but received {0}! This error occured on {1}.{2}: {3}</value>
   </data>
+  <data name="QueryableFiltering_ExpressionParameterInvalid" xml:space="preserve">
+    <value>Filtering needs a expression with exactly one parameter of type {0}! This error occured on {1}.{2}: {3}</value>
+  </data>
+  <data name="QueryableFilterProvider_ExpressionParameterInvalid" xml:space="preserve">
+    <value>Filtering needs a expression with exactly one parameter of type {0}! Check the expression on field {1}.</value>
+  </data>
   <data name="QueryableFiltering_NoMemberDeclared" xml:space="preserve">
     <value>Filtering needs a member of type PropertyInfo or MethodInfo no member was found! This error occured on {0}.{1}: {2}</value>
   </data>

src/HotChocolate/Data/src/Data/Filters/Convention/FilterConvention.cs

@@ -330,6 +330,12 @@ public bool IsOrAllowed()
         return false;
     }
 
+    public IFilterMetadata? CreateMetaData(
+        ITypeCompletionContext context,
+        IFilterInputTypeDefinition typeDefinition,
+        IFilterFieldDefinition fieldDefinition)
+        => _provider.CreateMetaData(context, typeDefinition, fieldDefinition);
+
     private bool TryCreateFilterType(
         IExtendedType runtimeType,
         [NotNullWhen(true)] out Type? type)

src/HotChocolate/Data/src/Data/Filters/Convention/FilterTypeInterceptor.cs

@@ -204,8 +204,12 @@ TypeSystemObjectBase Factory(IDescriptorContext _)
                         out IFilterFieldHandler? handler))
                     {
                         filterFieldDefinition.Handler = handler;
-                    }
-                    else
+                    } 
+
+                    filterFieldDefinition.Metadata =
+                        convention.CreateMetaData(completionContext, def, filterFieldDefinition);
+
+                    if (filterFieldDefinition.Handler is null)
                     {
                         throw ThrowHelper
                             .FilterInterceptor_NoHandlerFoundForField(def, filterFieldDefinition);

src/HotChocolate/Data/src/Data/Filters/Convention/IFilterConvention.cs

@@ -135,6 +135,14 @@ public interface IFilterConvention : IConvention
         IFilterFieldDefinition fieldDefinition,
         [NotNullWhen(true)] out IFilterFieldHandler? handler);
 
+    /// <summary>
+    /// Creates metadata for a field that the provider can pick up an use for the translation
+    /// </summary>
+    IFilterMetadata? CreateMetaData(
+        ITypeCompletionContext context,
+        IFilterInputTypeDefinition typeDefinition,
+        IFilterFieldDefinition fieldDefinition);
+
     /// <summary>
     /// Creates a middleware that represents the filter execution logic
     /// for the specified entity type.

src/HotChocolate/Data/src/Data/Filters/Expressions/ExpressionFilterMetadata.cs

@@ -0,0 +1,16 @@
+using System.Linq.Expressions;
+
+namespace HotChocolate.Data.Filters.Expressions;
+
+/// <summary>
+/// Defines meta that for a filter field that the provider can use to build the database query
+/// </summary>
+public class ExpressionFilterMetadata : IFilterMetadata
+{
+    public ExpressionFilterMetadata(Expression? expression)
+    {
+        Expression = expression;
+    }
+
+    public Expression? Expression { get; }
+}

src/HotChocolate/Data/src/Data/Filters/Expressions/Handlers/QueryableDefaultFieldHandler.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Diagnostics.CodeAnalysis;
+using System.Linq;
 using System.Linq.Expressions;
 using System.Reflection;
 using HotChocolate.Configuration;
@@ -28,7 +29,7 @@ public class QueryableDefaultFieldHandler
         IFilterInputTypeDefinition typeDefinition,
         IFilterFieldDefinition fieldDefinition) =>
         fieldDefinition is not FilterOperationFieldDefinition &&
-        fieldDefinition.Member is not null;
+        (fieldDefinition.Member is not null || fieldDefinition.Expression is not null);
 
     public override bool TryHandleEnter(
         QueryableFilterContext context,
@@ -51,20 +52,38 @@ public class QueryableDefaultFieldHandler
             return false;
         }
 
-        Expression nestedProperty = field.Member switch
+        Expression nestedProperty;
+        if (field.Metadata is ExpressionFilterMetadata { Expression: LambdaExpression expression })
         {
-            PropertyInfo propertyInfo =>
-                Expression.Property(context.GetInstance(), propertyInfo),
+            if (expression.Parameters.Count != 1 ||
+                expression.Parameters[0].Type != context.RuntimeTypes.Peek()!.Source)
+            {
+                throw ThrowHelper.QueryableFiltering_ExpressionParameterInvalid(
+                    field.RuntimeType.Source,
+                    field);
+            }
 
-            MethodInfo methodInfo =>
-                Expression.Call(context.GetInstance(), methodInfo),
+            nestedProperty = ReplaceVariableExpressionVisitor
+                .ReplaceParameter(expression, expression.Parameters[0], context.GetInstance())
+                .Body;
+        }
+        else
+        {
+            nestedProperty = field.Member switch
+            {
+                PropertyInfo propertyInfo =>
+                    Expression.Property(context.GetInstance(), propertyInfo),
 
-            null =>
-                throw ThrowHelper.QueryableFiltering_NoMemberDeclared(field),
+                MethodInfo methodInfo =>
+                    Expression.Call(context.GetInstance(), methodInfo),
 
-            _ =>
-                throw ThrowHelper.QueryableFiltering_MemberInvalid(field.Member, field)
-        };
+                null =>
+                    throw ThrowHelper.QueryableFiltering_NoMemberDeclared(field),
+
+                _ =>
+                    throw ThrowHelper.QueryableFiltering_MemberInvalid(field.Member, field)
+            };
+        }
 
         context.PushInstance(nestedProperty);
         context.RuntimeTypes.Push(field.RuntimeType);
@@ -101,4 +120,34 @@ public class QueryableDefaultFieldHandler
         action = SyntaxVisitor.Continue;
         return true;
     }
+
+    private sealed class ReplaceVariableExpressionVisitor : ExpressionVisitor
+    {
+        private readonly Expression _replacement;
+        private readonly ParameterExpression _parameter;
+
+        public ReplaceVariableExpressionVisitor(
+            Expression replacement,
+            ParameterExpression parameter)
+        {
+            _replacement = replacement;
+            _parameter = parameter;
+        }
+
+        protected override Expression VisitParameter(ParameterExpression node)
+        {
+            if (node == _parameter)
+            {
+                return _replacement;
+            }
+            return base.VisitParameter(node);
+        }
+
+        public static LambdaExpression ReplaceParameter(
+            LambdaExpression lambda,
+            ParameterExpression parameter,
+            Expression replacement)
+            => (LambdaExpression)
+                new ReplaceVariableExpressionVisitor(replacement, parameter).Visit(lambda);
+    }
 }

src/HotChocolate/Data/src/Data/Filters/Expressions/QueryableFilterProvider.cs

@@ -4,6 +4,7 @@
 using System.Linq;
 using System.Linq.Expressions;
 using System.Threading.Tasks;
+using HotChocolate.Configuration;
 using HotChocolate.Language;
 using HotChocolate.Resolvers;
 using HotChocolate.Types;
@@ -150,4 +151,27 @@ private static ApplyFiltering CreateApplicator<TEntityType>(NameString argumentN
         contextData[ContextVisitFilterArgumentKey] = argumentKey;
         contextData[ContextArgumentNameKey] = argumentName;
     }
+
+    public override IFilterMetadata? CreateMetaData(
+        ITypeCompletionContext context,
+        IFilterInputTypeDefinition typeDefinition,
+        IFilterFieldDefinition fieldDefinition)
+    {
+        if (fieldDefinition.Expression is not null)
+        {
+            if (fieldDefinition.Expression is not LambdaExpression lambda ||
+                lambda.Parameters.Count != 1 ||
+                lambda.Parameters[0].Type != typeDefinition.EntityType)
+            {
+                throw ThrowHelper.QueryableFilterProvider_ExpressionParameterInvalid(
+                    context.Type,
+                    typeDefinition,
+                    fieldDefinition);
+            }
+
+            return new ExpressionFilterMetadata(fieldDefinition.Expression);
+        }
+
+        return null;
+    }
 }

src/HotChocolate/Data/src/Data/Filters/Fields/FilterField.cs

@@ -20,6 +20,7 @@ internal FilterField(FilterFieldDefinition definition, int index)
     {
         Member = definition.Member;
         Handler = definition.Handler!;
+        Metadata = definition.Metadata;
     }
 
     public new FilterInputType DeclaringType => (FilterInputType)base.DeclaringType;
@@ -32,6 +33,8 @@ internal FilterField(FilterFieldDefinition definition, int index)
 
     public IFilterFieldHandler Handler { get; }
 
+    public IFilterMetadata? Metadata { get; }
+
     protected override void OnCompleteField(
         ITypeCompletionContext context,
         ITypeSystemMember declaringMember,
@@ -43,5 +46,9 @@ internal FilterField(FilterFieldDefinition definition, int index)
         {
             RuntimeType = context.TypeInspector.GetReturnType(Member, ignoreAttributes: true);
         }
+        else if (base.RuntimeType is { } runtimeType)
+        {
+            RuntimeType = context.TypeInspector.GetType(runtimeType);
+        }
     }
 }

src/HotChocolate/Data/src/Data/Filters/Fields/IFilterField.cs

@@ -16,4 +16,6 @@ public interface IFilterField : IInputField
     new IExtendedType? RuntimeType { get; }
 
     IFilterFieldHandler Handler { get; }
+
+    IFilterMetadata? Metadata { get; }
 }

src/HotChocolate/Data/src/Data/Filters/FilterFieldDefinition.cs

@@ -1,6 +1,8 @@
+using System.Linq.Expressions; 
 using System;
-using System.Collections.Generic;
+using System.Collections.Generic; 
 using System.Reflection;
+using HotChocolate.Internal;
 using HotChocolate.Types;
 using HotChocolate.Types.Descriptors;
 using HotChocolate.Types.Descriptors.Definitions;
@@ -18,7 +20,11 @@ public class FilterFieldDefinition
 
     public IFilterFieldHandler? Handler { get; set; }
 
-    public string? Scope { get; set; }
+    public Expression? Expression { get; set; }
+
+    internal IFilterMetadata? Metadata { get; set; }
+
+    public string? Scope { get; set; } 
 
     public List<int> AllowedOperations => _allowedOperations ??= new List<int>();
 
@@ -65,5 +71,5 @@ internal void MergeInto(FilterFieldDefinition target)
         {
             target.CreateFieldTypeDefinition = CreateFieldTypeDefinition;
         }
-    }
+    } 
 }

src/HotChocolate/Data/src/Data/Filters/FilterFieldDescriptor.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Linq.Expressions;
 using System.Reflection;
 using HotChocolate.Language;
 using HotChocolate.Types;
@@ -38,6 +39,23 @@ public class FilterFieldDescriptor
         Definition.Scope = scope;
     }
 
+    protected FilterFieldDescriptor(
+        IDescriptorContext context,
+        string? scope,
+        Expression expression)
+        : base(context)
+    {
+        IFilterConvention convention = context.GetFilterConvention(scope);
+
+        Definition.Expression = expression;
+        Definition.Scope = scope;
+        if (Definition.Expression is LambdaExpression lambda)
+        {
+            Definition.Type = convention.GetFieldType(lambda.ReturnType);
+            Definition.RuntimeType = lambda.ReturnType;
+        }
+    }
+
     protected internal FilterFieldDescriptor(
         IDescriptorContext context,
         string? scope)
@@ -171,4 +189,10 @@ public new IFilterFieldDescriptor Directive<TDirective>()
         NameString fieldName,
         string? scope) =>
         new FilterFieldDescriptor(context, scope, fieldName);
+
+    internal static FilterFieldDescriptor New(
+        IDescriptorContext context,
+        string? scope,
+        Expression expression) =>
+        new FilterFieldDescriptor(context, scope, expression);
 }

src/HotChocolate/Data/src/Data/Filters/FilterInputTypeDescriptor`1.cs

@@ -99,23 +99,31 @@ public new IFilterInputTypeDescriptor<T> BindFieldsImplicitly()
     /// <inheritdoc />
     public IFilterFieldDescriptor Field<TField>(Expression<Func<T, TField>> propertyOrMember)
     {
-        if (propertyOrMember.ExtractMember() is PropertyInfo m)
+        switch (propertyOrMember.TryExtractMember())
         {
-            FilterFieldDescriptor? fieldDescriptor =
-                Fields.FirstOrDefault(t => t.Definition.Member == m);
-
-            if (fieldDescriptor is null)
-            {
-                fieldDescriptor = FilterFieldDescriptor.New(Context, Definition.Scope, m);
+            case PropertyInfo m:
+                FilterFieldDescriptor? fieldDescriptor =
+                    Fields.FirstOrDefault(t => t.Definition.Member == m);
+
+                if (fieldDescriptor is null)
+                {
+                    fieldDescriptor = FilterFieldDescriptor.New(Context, Definition.Scope, m);
+                    Fields.Add(fieldDescriptor);
+                }
+
+                return fieldDescriptor;
+
+            case MethodInfo m:
+                throw new ArgumentException(
+                    FilterInputTypeDescriptor_Field_OnlyProperties,
+                    nameof(propertyOrMember));
+
+            default:
+                fieldDescriptor = FilterFieldDescriptor
+                    .New(Context, Definition.Scope, propertyOrMember);
                 Fields.Add(fieldDescriptor);
-            }
-
-            return fieldDescriptor;
+                return fieldDescriptor;
         }
-
-        throw new ArgumentException(
-            FilterInputTypeDescriptor_Field_OnlyProperties,
-            nameof(propertyOrMember));
     }
 
     /// <inheritdoc />