MonoRail/Castle.MonoRail.Views.Brail/FixTryGetParameterConditionalChecks.cs

   1 namespace Castle.MonoRail.Views.Brail
   2 {
   3         using Boo.Lang.Compiler.Ast;
   4         using Boo.Lang.Compiler.Steps;
   5
   6         /// <summary>
   7         /// We need to handle the following code:
   8         /// if ?Error:
   9         /// end
  10         ///
  11         /// However, because ?Op will return an IgnoreNull object, we can't just
  12         /// use the default boo behavior, but need to fix it up
  13         /// </summary>
  14         public class FixTryGetParameterConditionalChecks : AbstractNamespaceSensitiveTransformerCompilerStep
  15         {
  16                 public override void Run()
  17                 {
  18                         Visit(CompileUnit);
  19                 }
  20
  21                 public override void OnBinaryExpression(BinaryExpression node)
  22                 {
  23                         if (node.Operator != BinaryOperatorType.Equality)
  24                                 return;
  25
  26                         if (IsTryGetParameterInvocation(node.Left) == false &&
  27                             IsTryGetParameterInvocation(node.Right) == false)
  28                                 return;
  29
  30                         MethodInvocationExpression mie = new MethodInvocationExpression();
  31                         ReferenceExpression expression = AstUtil.CreateReferenceExpression("Castle.MonoRail.Views.Brail.IgnoreNull.AreEqual");
  32                         mie.Target = expression;
  33                         mie.Arguments.Add(node.Left);
  34                         mie.Arguments.Add(node.Right);
  35
  36                         ReplaceCurrentNode(mie);
  37                 }
  38
  39
  40                 public override void OnIfStatement(IfStatement node)
  41                 {
  42                         base.OnIfStatement(node);
  43                         node.Condition = FixCondition(node.Condition);
  44                 }
  45
  46                 public override void OnUnlessStatement(UnlessStatement node)
  47                 {
  48                         base.OnUnlessStatement(node);
  49                         node.Condition = FixCondition(node.Condition);
  50                 }
  51
  52                 private Expression FixCondition(Expression condition)
  53                 {
  54                         if (IsTryGetParameterInvocation(condition) == false)
  55                                 return condition;
  56
  57                         string name = ((ReferenceExpression) condition).Name.Substring(1);
  58                         condition = new MethodInvocationExpression(
  59                                 new MemberReferenceExpression(new SuperLiteralExpression(), "TryGetParameter"),
  60                                 new StringLiteralExpression(name)
  61                                 );
  62
  63                         MemberReferenceExpression isNull =
  64                 new MemberReferenceExpression(condition, "_IsIgnoreNullReferencingNotNullObject_");
  65
  66                         return isNull;
  67                 }
  68
  69                 private static bool IsTryGetParameterInvocation(Expression condition)
  70                 {
  71                         ReferenceExpression expression = condition as ReferenceExpression;
  72                         if (expression == null)
  73                                 return false;
  74
  75                         return expression.Name.StartsWith("?");
  76                 }
  77         }
  78 }