#11 Custom expression visitors can be added to the QbservableServiceO…

…ptions instance that you pass to the service operators/factories.
RxDave · Jun 22, 2016 · 41b08af · 41b08af
1 parent dce014f
commit 41b08af
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Showing 3 changed files with 52 additions and 27 deletions.
diff --git a/Source/Qactive.Providers.Streaming/StreamQbservableProtocol.cs b/Source/Qactive.Providers.Streaming/StreamQbservableProtocol.cs
@@ -19,7 +19,7 @@ internal sealed class StreamQbservableProtocol : QbservableProtocol<Stream, Stre
     private readonly IRemotingFormatter formatter;
 
     public StreamQbservableProtocol(object clientId, Stream stream, IRemotingFormatter formatter, CancellationToken cancel)
-    : base(clientId, stream, cancel)
+      : base(clientId, stream, cancel)
     {
       Contract.Requires(clientId != null);
       Contract.Requires(stream != null);
@@ -32,7 +32,7 @@ public StreamQbservableProtocol(object clientId, Stream stream, IRemotingFormatt
     }
 
     public StreamQbservableProtocol(Stream stream, IRemotingFormatter formatter, QbservableServiceOptions serviceOptions, CancellationToken cancel)
-    : base(stream, serviceOptions, cancel)
+      : base(stream, serviceOptions, cancel)
     {
       Contract.Requires(stream != null);
       Contract.Requires(formatter != null);

diff --git a/Source/Qactive/QbservableServiceOptions.cs b/Source/Qactive/QbservableServiceOptions.cs
@@ -1,5 +1,8 @@
 using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Diagnostics.Contracts;
+using System.Linq.Expressions;
 
 namespace Qactive
 {
@@ -11,26 +14,35 @@ public sealed class QbservableServiceOptions
     [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Security", "CA2104:DoNotDeclareReadOnlyMutableReferenceTypes", Justification = "It's immutable due to the frozen flag.")]
     public static readonly QbservableServiceOptions Default = new QbservableServiceOptions()
     {
-      frozen = true,
+      IsFrozen = true,
       evaluationContext = new ServiceEvaluationContext()
     };
 
     [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Security", "CA2104:DoNotDeclareReadOnlyMutableReferenceTypes", Justification = "It's immutable due to the frozen flag.")]
     public static readonly QbservableServiceOptions Unrestricted = new QbservableServiceOptions()
     {
-      frozen = true,
+      IsFrozen = true,
       allowExpressionsUnrestricted = true,
       enableDuplex = true,
       evaluationContext = new ServiceEvaluationContext()
     };
 
-    private bool frozen;
+    private readonly List<ExpressionVisitor> visitors = new List<ExpressionVisitor>();
     private bool sendServerErrorsToClients;
     private bool enableDuplex;
     private bool allowExpressionsUnrestricted;
     private ExpressionOptions expressionOptions;
     private ServiceEvaluationContext evaluationContext;
 
+    [ContractInvariantMethod]
+    [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1822:MarkMembersAsStatic", Justification = "Required for code contracts.")]
+    private void ObjectInvariant()
+    {
+      Contract.Invariant(visitors != null);
+    }
+
+    public bool IsFrozen { get; private set; }
+
     public bool SendServerErrorsToClients
     {
       get
@@ -39,10 +51,7 @@ public bool SendServerErrorsToClients
       }
       set
       {
-        if (frozen)
-        {
-          throw new NotSupportedException();
-        }
+        Contract.Requires(!IsFrozen);
 
         sendServerErrorsToClients = value;
       }
@@ -56,10 +65,7 @@ public bool EnableDuplex
       }
       set
       {
-        if (frozen)
-        {
-          throw new NotSupportedException();
-        }
+        Contract.Requires(!IsFrozen);
 
         enableDuplex = value;
       }
@@ -73,15 +79,18 @@ public bool AllowExpressionsUnrestricted
       }
       set
       {
-        if (frozen)
-        {
-          throw new NotSupportedException();
-        }
+        Contract.Requires(!IsFrozen);
 
         allowExpressionsUnrestricted = value;
       }
     }
 
+#if READONLYCOLLECTIONS
+    public IReadOnlyList<ExpressionVisitor> Visitors => visitors.AsReadOnly();
+#else
+    public ReadOnlyCollection<ExpressionVisitor> Visitors => visitors.AsReadOnly();
+#endif
+
     public ExpressionOptions ExpressionOptions
     {
       get
@@ -90,10 +99,7 @@ public ExpressionOptions ExpressionOptions
       }
       set
       {
-        if (frozen)
-        {
-          throw new NotSupportedException();
-        }
+        Contract.Requires(!IsFrozen);
 
         expressionOptions = value;
       }
@@ -114,22 +120,21 @@ public ServiceEvaluationContext EvaluationContext
       }
       set
       {
-        if (frozen)
-        {
-          throw new NotSupportedException();
-        }
+        Contract.Requires(!IsFrozen);
 
         evaluationContext = value;
       }
     }
 
     public QbservableServiceOptions()
     {
+      Contract.Ensures(!IsFrozen);
     }
 
     public QbservableServiceOptions(QbservableServiceOptions clone)
     {
       Contract.Requires(clone != null);
+      Contract.Ensures(!IsFrozen);
 
       sendServerErrorsToClients = clone.sendServerErrorsToClients;
       enableDuplex = clone.enableDuplex;
@@ -138,17 +143,32 @@ public QbservableServiceOptions(QbservableServiceOptions clone)
       evaluationContext = clone.evaluationContext;
     }
 
+    public QbservableServiceOptions Add(ExpressionVisitor visitor)
+    {
+      Contract.Requires(visitor != null);
+      Contract.Requires(!IsFrozen);
+      Contract.Ensures(Contract.Result<QbservableServiceOptions>() == this);
+      Contract.Ensures(Visitors.Count == Contract.OldValue(Visitors.Count) + 1);
+      Contract.Ensures(Contract.Exists(Visitors, v => v == visitor));
+
+      visitors.Add(visitor);
+
+      return this;
+    }
+
     public QbservableServiceOptions Freeze()
     {
-      Contract.Ensures(Contract.Result<QbservableServiceOptions>() != null);
+      Contract.Ensures(Contract.Result<QbservableServiceOptions>() == this);
+      Contract.Ensures(IsFrozen);
 
-      frozen = true;
+      IsFrozen = true;
       return this;
     }
 
     public QbservableServiceOptions Clone()
     {
       Contract.Ensures(Contract.Result<QbservableServiceOptions>() != null);
+      Contract.Ensures(!Contract.Result<QbservableServiceOptions>().IsFrozen);
 
       return new QbservableServiceOptions(this);
     }

diff --git a/Source/Qactive/ServerQuery.cs b/Source/Qactive/ServerQuery.cs
@@ -135,6 +135,11 @@ private Expression PrepareExpression(out IQbservableProvider realProvider)
 
       preparedExpression = visitor.Visit(preparedExpression);
 
+      foreach (var customVisitor in Provider.Options.Visitors)
+      {
+        preparedExpression = customVisitor.Visit(preparedExpression);
+      }
+
       Log.ServerRewrittenExpression(clientId, preparedExpression);
 
       return preparedExpression;