Query: Introduce custom query root for TVF

- Avoids having to do special processing in other visitors
- Visit's method's argument correctly in other visitor (this means that if there is a navigation expansion required for a parameter it will be done automatically)
- Remove Nav expansion factory not needed anymore
- Rename ExpressionPrinter.VisitList to VisitCollection and take IReadOnlyCollection, that is what most expression uses.
- Remove unnecessary exception message. They are part of a larger work item.

Resolves #20146

src/EFCore.Cosmos/Query/Internal/SqlFunctionExpression.cs

@@ -110,7 +110,7 @@ public override void Print(ExpressionPrinter expressionPrinter)
 
             expressionPrinter.Append(Name);
             expressionPrinter.Append("(");
-            expressionPrinter.VisitList(Arguments);
+            expressionPrinter.VisitCollection(Arguments);
             expressionPrinter.Append(")");
         }
 

src/EFCore.Relational/Infrastructure/EntityFrameworkRelationalServicesBuilder.cs

@@ -169,7 +169,6 @@ public override EntityFrameworkServicesBuilder TryAddCoreServices()
             TryAdd<IQueryTranslationPreprocessorFactory, RelationalQueryTranslationPreprocessorFactory>();
             TryAdd<IRelationalParameterBasedQueryTranslationPostprocessorFactory, RelationalParameterBasedQueryTranslationPostprocessorFactory>();
             TryAdd<IRelationalQueryStringFactory, RelationalQueryStringFactory>();
-            TryAdd<INavigationExpandingExpressionVisitorFactory, RelationalNavigationExpandingExpressionVisitorFactory>();
 
             ServiceCollectionMap.GetInfrastructure()
                 .AddDependencySingleton<RelationalSqlGenerationHelperDependencies>()

src/EFCore.Relational/Properties/RelationalStrings.resx

@@ -423,12 +423,6 @@
   <data name="DbFunctionInvalidInstanceType" xml:space="preserve">
     <value>The DbFunction '{function}' defined on type '{type}' must be either a static method or an instance method defined on a DbContext subclass. Instance methods on other types are not supported.</value>
   </data>
-  <data name="DbFunctionCantProjectIQueryable" xml:space="preserve">
-    <value>Queryable Db Functions used in projections cannot return IQueryable.  IQueryable must be converted to a collection type such as List or Array.</value>
-  </data>
-  <data name="DbFunctionProjectedCollectionMustHavePK" xml:space="preserve">
-    <value>Return type of a queryable function '{functionName}' which is used in a projected collection must define a primary key.</value>
-  </data>
   <data name="ConflictingAmbientTransaction" xml:space="preserve">
     <value>An ambient transaction has been detected. The ambient transaction needs to be completed before beginning a transaction on this connection.</value>
   </data>

src/EFCore.Relational/Query/Internal/QueryableFunctionQueryRootExpression.cs

@@ -0,0 +1,80 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Linq.Expressions;
+using JetBrains.Annotations;
+using Microsoft.EntityFrameworkCore.Internal;
+using Microsoft.EntityFrameworkCore.Metadata;
+using Microsoft.EntityFrameworkCore.Utilities;
+
+namespace Microsoft.EntityFrameworkCore.Query.Internal
+{
+    public class QueryableFunctionQueryRootExpression : QueryRootExpression
+    {
+        //Since this is always generated while compiling there is no query provider associated
+        public QueryableFunctionQueryRootExpression(
+            [NotNull] IEntityType entityType, [NotNull] IDbFunction function, [NotNull] IReadOnlyCollection<Expression> arguments)
+            : base(entityType)
+        {
+            Check.NotNull(function, nameof(function));
+            Check.NotNull(arguments, nameof(arguments));
+
+            Function = function;
+            Arguments = arguments;
+        }
+
+        public virtual IDbFunction Function { get; }
+        public virtual IReadOnlyCollection<Expression> Arguments { get; }
+
+        protected override Expression VisitChildren(ExpressionVisitor visitor)
+        {
+            var arguments = new List<Expression>();
+            var changed = false;
+            foreach (var argument in Arguments)
+            {
+                var newArgument = visitor.Visit(argument);
+                arguments.Add(newArgument);
+                changed |= argument != newArgument;
+            }
+
+            return changed
+                ? new QueryableFunctionQueryRootExpression(EntityType, Function, arguments)
+                : this;
+        }
+
+        public override void Print(ExpressionPrinter expressionPrinter)
+        {
+            expressionPrinter.Append(Function.MethodInfo.DisplayName());
+            expressionPrinter.Append("(");
+            expressionPrinter.VisitCollection(Arguments);
+            expressionPrinter.Append(")");
+        }
+
+        public override bool Equals(object obj)
+            => obj != null
+                && (ReferenceEquals(this, obj)
+                    || obj is QueryableFunctionQueryRootExpression queryRootExpression
+                    && Equals(queryRootExpression));
+
+        private bool Equals(QueryableFunctionQueryRootExpression queryRootExpression)
+            => base.Equals(queryRootExpression)
+                && Equals(Function, queryRootExpression.Function)
+                && Arguments.SequenceEqual(queryRootExpression.Arguments, ExpressionEqualityComparer.Instance);
+
+        public override int GetHashCode()
+        {
+            var hashCode = new HashCode();
+            hashCode.Add(base.GetHashCode());
+            hashCode.Add(Function);
+            foreach (var item in Arguments)
+            {
+                hashCode.Add(item);
+            }
+
+            return hashCode.ToHashCode();
+        }
+    }
+}

src/EFCore.Relational/Query/Internal/QueryableFunctionToQueryRootConvertingExpressionVisitor.cs

@@ -0,0 +1,40 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Collections.Generic;
+using System.Linq.Expressions;
+using JetBrains.Annotations;
+using Microsoft.EntityFrameworkCore.Metadata;
+using Microsoft.EntityFrameworkCore.Utilities;
+
+namespace Microsoft.EntityFrameworkCore.Query.Internal
+{
+    public class QueryableFunctionToQueryRootConvertingExpressionVisitor : ExpressionVisitor
+    {
+        private readonly IModel _model;
+
+        public QueryableFunctionToQueryRootConvertingExpressionVisitor([NotNull] IModel model)
+        {
+            Check.NotNull(model, nameof(model));
+
+            _model = model;
+        }
+
+        protected override Expression VisitMethodCall(MethodCallExpression methodCallExpression)
+        {
+            var function = _model.FindDbFunction(methodCallExpression.Method);
+
+            return function?.IsIQueryable == true
+                ? CreateQueryableFunctionQueryRootExpression(function, methodCallExpression.Arguments)
+                : base.VisitMethodCall(methodCallExpression);
+        }
+
+        private Expression CreateQueryableFunctionQueryRootExpression(
+            IDbFunction function, IReadOnlyCollection<Expression> arguments)
+        {
+            var entityType = _model.FindEntityType(function.MethodInfo.ReturnType.GetGenericArguments()[0]);
+
+            return new QueryableFunctionQueryRootExpression(entityType, function, arguments);
+        }
+    }
+}

src/EFCore.Relational/Query/Internal/RelationalProjectionBindingExpressionVisitor.cs

@@ -246,11 +246,6 @@ protected override Expression VisitNew(NewExpression newExpression)
                 return null;
             }
 
-            if (newExpression.Arguments.Any(arg => arg is MethodCallExpression methodCallExp && _model.FindDbFunction(methodCallExp.Method)?.IsIQueryable == true))
-            {
-                throw new InvalidOperationException(RelationalStrings.DbFunctionCantProjectIQueryable());
-            }
-
             var newArguments = new Expression[newExpression.Arguments.Count];
             for (var i = 0; i < newArguments.Length; i++)
             {

src/EFCore.Relational/Query/Internal/RelationalQueryTranslationPreprocessorFactory.cs

@@ -21,23 +21,20 @@ public class RelationalQueryTranslationPreprocessorFactory : IQueryTranslationPr
     {
         private readonly QueryTranslationPreprocessorDependencies _dependencies;
         private readonly RelationalQueryTranslationPreprocessorDependencies _relationalDependencies;
-        private readonly INavigationExpandingExpressionVisitorFactory _navigationExpandingExpressionVisitorFactory;
 
         public RelationalQueryTranslationPreprocessorFactory(
             [NotNull] QueryTranslationPreprocessorDependencies dependencies,
-            [NotNull] RelationalQueryTranslationPreprocessorDependencies relationalDependencies,
-            [NotNull] INavigationExpandingExpressionVisitorFactory navigationExpandingExpressionVisitorFactory)
+            [NotNull] RelationalQueryTranslationPreprocessorDependencies relationalDependencies)
         {
             _dependencies = dependencies;
             _relationalDependencies = relationalDependencies;
-            _navigationExpandingExpressionVisitorFactory = navigationExpandingExpressionVisitorFactory;
         }
 
         public virtual QueryTranslationPreprocessor Create(QueryCompilationContext queryCompilationContext)
         {
             Check.NotNull(queryCompilationContext, nameof(queryCompilationContext));
 
-            return new RelationalQueryTranslationPreprocessor(_dependencies, _relationalDependencies, queryCompilationContext, _navigationExpandingExpressionVisitorFactory);
+            return new RelationalQueryTranslationPreprocessor(_dependencies, _relationalDependencies, queryCompilationContext);
         }
     }
 }

src/EFCore.Relational/Query/RelationalEvaluatableExpressionFilter.cs

@@ -47,11 +47,11 @@ public RelationalEvaluatableExpressionFilter(
         /// </summary>
         protected virtual RelationalEvaluatableExpressionFilterDependencies RelationalDependencies { get; }
 
-        /// <summary>	
-        ///     Checks whether the given expression can be evaluated.	
-        /// </summary>	
-        /// <param name="expression"> The expression. </param>	
-        /// <param name="model"> The model. </param>	
+        /// <summary>
+        ///     Checks whether the given expression can be evaluated.
+        /// </summary>
+        /// <param name="expression"> The expression. </param>
+        /// <param name="model"> The model. </param>
         /// <returns> True if the expression can be evaluated; false otherwise. </returns>
         public override bool IsEvaluatableExpression(Expression expression, IModel model)
         {
@@ -67,7 +67,7 @@ public override bool IsEvaluatableExpression(Expression expression, IModel model
             return base.IsEvaluatableExpression(expression, model);
         }
 
-        public override bool IsQueryableFunction(Expression expression, IModel model) => 
+        public override bool IsQueryableFunction(Expression expression, IModel model) =>
             expression is MethodCallExpression methodCallExpression
                && model.FindDbFunction(methodCallExpression.Method)?.IsIQueryable == true;
     }

src/EFCore.Relational/Query/RelationalQueryTranslationPreprocessor.cs

@@ -1,7 +1,9 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System.Linq.Expressions;
 using JetBrains.Annotations;
+using Microsoft.EntityFrameworkCore.Query.Internal;
 using Microsoft.EntityFrameworkCore.Utilities;
 
 namespace Microsoft.EntityFrameworkCore.Query
@@ -11,15 +13,22 @@ public class RelationalQueryTranslationPreprocessor : QueryTranslationPreprocess
         public RelationalQueryTranslationPreprocessor(
             [NotNull] QueryTranslationPreprocessorDependencies dependencies,
             [NotNull] RelationalQueryTranslationPreprocessorDependencies relationalDependencies,
-            [NotNull] QueryCompilationContext queryCompilationContext,
-            [NotNull] INavigationExpandingExpressionVisitorFactory navigationExpandingExpressionVisitorFactory)
-            : base(dependencies, queryCompilationContext, navigationExpandingExpressionVisitorFactory)
+            [NotNull] QueryCompilationContext queryCompilationContext)
+            : base(dependencies, queryCompilationContext)
         {
             Check.NotNull(relationalDependencies, nameof(relationalDependencies));
 
             RelationalDependencies = relationalDependencies;
         }
 
         protected virtual RelationalQueryTranslationPreprocessorDependencies RelationalDependencies { get; }
+
+        public override Expression NormalizeQueryableMethodCall(Expression expression)
+        {
+            expression = base.NormalizeQueryableMethodCall(expression);
+            expression = new QueryableFunctionToQueryRootConvertingExpressionVisitor(QueryCompilationContext.Model).Visit(expression);
+
+            return expression;
+        }
     }
 }