mcs/class/System.Core/System.Linq/QueryableTransformer.cs

   1 //
   2 // QueryableTransformer.cs
   3 //
   4 // Authors:
   5 //      Roei Erez (roeie@mainsoft.com)
   6 //      Jb Evain (jbevain@novell.com)
   7 //
   8 // Copyright (C) 2008 Novell, Inc (http://www.novell.com)
   9 //
  10 // Permission is hereby granted, free of charge, to any person obtaining
  11 // a copy of this software and associated documentation files (the
  12 // "Software"), to deal in the Software without restriction, including
  13 // without limitation the rights to use, copy, modify, merge, publish,
  14 // distribute, sublicense, and/or sell copies of the Software, and to
  15 // permit persons to whom the Software is furnished to do so, subject to
  16 // the following conditions:
  17 //
  18 // The above copyright notice and this permission notice shall be
  19 // included in all copies or substantial portions of the Software.
  20 //
  21 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
  22 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  23 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
  24 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
  25 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
  26 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
  27 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  28 //
  29
  30 using System;
  31 using System.Collections;
  32 using System.Collections.Generic;
  33 using System.Collections.ObjectModel;
  34 using System.Linq;
  35 using System.Linq.Expressions;
  36 using System.Reflection;
  37 using System.Runtime.CompilerServices;
  38
  39 namespace System.Linq {
  40
  41         class QueryableTransformer : ExpressionTransformer {
  42
  43                 protected override Expression VisitMethodCall (MethodCallExpression methodCall)
  44                 {
  45                         if (IsQueryableExtension (methodCall.Method))
  46                                 return ReplaceQueryableMethod (methodCall);
  47
  48                         return base.VisitMethodCall (methodCall);
  49                 }
  50
  51                 protected override Expression VisitLambda (LambdaExpression lambda)
  52                 {
  53                         return lambda;
  54                 }
  55
  56                 protected override Expression VisitConstant (ConstantExpression constant)
  57                 {
  58                         var qe = constant.Value as IQueryableEnumerable;
  59                         if (qe == null)
  60                                 return constant;
  61
  62                         var enumerable = qe.GetEnumerable ();
  63                         if (enumerable != null)
  64                                 return Expression.Constant (enumerable);
  65
  66                         return Visit (qe.Expression);
  67                 }
  68
  69                 static bool IsQueryableExtension (MethodInfo method)
  70                 {
  71                         return HasExtensionAttribute (method) &&
  72                                 method.GetParameters () [0].ParameterType.IsAssignableTo (typeof (IQueryable));
  73                 }
  74
  75                 static bool HasExtensionAttribute (MethodInfo method)
  76                 {
  77                         return method.GetCustomAttributes (typeof (ExtensionAttribute), false).Length > 0;
  78                 }
  79
  80                 MethodCallExpression ReplaceQueryableMethod (MethodCallExpression old)
  81                 {
  82                         Expression target = null;
  83                         if (old.Object != null)
  84                                 target = Visit (old.Object);
  85
  86                         var method = ReplaceQueryableMethod (old.Method);
  87                         var parameters = method.GetParameters ();
  88                         var arguments = new Expression [old.Arguments.Count];
  89
  90                         for (int i = 0; i < arguments.Length; i++) {
  91                                 arguments [i] = UnquoteIfNeeded (
  92                                         Visit (old.Arguments [i]),
  93                                         parameters [i].ParameterType);
  94                         }
  95
  96                         return Expression.Call (target, method, arguments);
  97                 }
  98
  99                 static Expression UnquoteIfNeeded (Expression expression, Type delegateType)
 100                 {
 101                         if (expression.NodeType != ExpressionType.Quote)
 102                                 return expression;
 103
 104                         var lambda = (LambdaExpression) ((UnaryExpression) expression).Operand;
 105                         if (lambda.Type == delegateType)
 106                                 return lambda;
 107
 108                         return expression;
 109                 }
 110
 111                 static Type GetTargetDeclaringType (MethodInfo method)
 112                 {
 113                         return method.DeclaringType == typeof (Queryable) ? typeof (Enumerable) : method.DeclaringType;
 114                 }
 115
 116                 static MethodInfo ReplaceQueryableMethod (MethodInfo method)
 117                 {
 118                         var target_type = GetTargetDeclaringType (method);
 119                         var result = GetMatchingMethod (method, target_type);
 120
 121                         if (result != null)
 122                                 return result;
 123
 124                         throw new InvalidOperationException (
 125                                 string.Format (
 126                                         "There is no method {0} on type {1} that matches the specified arguments",
 127                                         method.Name,
 128                                         target_type.FullName));
 129                 }
 130
 131                 static MethodInfo GetMatchingMethod (MethodInfo method, Type declaring)
 132                 {
 133                         foreach (var candidate in declaring.GetMethods ()) {
 134                                 if (!MethodMatch (candidate, method))
 135                                         continue;
 136
 137                                 if (method.IsGenericMethod)
 138                                         return candidate.MakeGenericMethodFrom (method);
 139
 140                                 return candidate;
 141                         }
 142
 143                         return null;
 144                 }
 145
 146                 static bool MethodMatch (MethodInfo candidate, MethodInfo method)
 147                 {
 148                         if (candidate.Name != method.Name)
 149                                 return false;
 150
 151                         if (!HasExtensionAttribute (candidate))
 152                                 return false;
 153
 154                         var parameters = method.GetParameterTypes ();
 155
 156                         if (parameters.Length != candidate.GetParameters ().Length)
 157                                 return false;
 158
 159                         if (method.IsGenericMethod) {
 160                                 if (!candidate.IsGenericMethod)
 161                                         return false;
 162
 163                                 if (candidate.GetGenericArguments ().Length != method.GetGenericArguments ().Length)
 164                                         return false;
 165
 166                                 candidate = candidate.MakeGenericMethodFrom (method);
 167                         }
 168
 169                         if (!TypeMatch (candidate.ReturnType, method.ReturnType))
 170                                 return false;
 171
 172                         var candidate_parameters = candidate.GetParameterTypes ();
 173
 174                         if (candidate_parameters [0] != GetComparableType (parameters [0]))
 175                                 return false;
 176
 177                         for (int i = 1; i < candidate_parameters.Length; ++i)
 178                                 if (!TypeMatch (candidate_parameters [i], parameters [i]))
 179                                         return false;
 180
 181                         return true;
 182                 }
 183
 184                 static bool TypeMatch (Type candidate, Type type)
 185                 {
 186                         if (candidate == type)
 187                                 return true;
 188
 189                         return candidate == GetComparableType (type);
 190                 }
 191
 192                 static Type GetComparableType (Type type)
 193                 {
 194                         if (type.IsGenericInstanceOf (typeof (IQueryable<>)))
 195                                 type = typeof (IEnumerable<>).MakeGenericTypeFrom (type);
 196                         else if (type.IsGenericInstanceOf (typeof (IOrderedQueryable<>)))
 197                                 type = typeof (IOrderedEnumerable<>).MakeGenericTypeFrom (type);
 198                         else if (type.IsGenericInstanceOf (typeof (Expression<>)))
 199                                 type = type.GetFirstGenericArgument ();
 200                         else if (type == typeof (IQueryable))
 201                                 type = typeof (IEnumerable);
 202
 203                         return type;
 204                 }
 205         }
 206 }