public static bool IsMatch(this Expression expression, out Match match)
{
if (expression is MatchExpression matchExpression)
{
match = matchExpression.Match;
return(true);
}
using (var observer = MatcherObserver.Activate())
{
Expression.Lambda <Action>(expression).CompileUsingExpressionCompiler().Invoke();
return(observer.TryGetLastMatch(out match));
}
}
public override Expression <Action <T> > ReconstructExpression <T>(Action <T> action, object[] ctorArgs = null)
{
using (var matcherObserver = MatcherObserver.Activate())
{
// Create the root recording proxy:
var root = (T)CreateProxy(typeof(T), ctorArgs, matcherObserver, out var rootRecorder);
Exception error = null;
try
{
// Execute the delegate. The root recorder will automatically "mock" return values
// and so build a chain of recorders, whereby each one records a single invocation
// in a method chain `o.X.Y.Z`:
action.Invoke(root);
}
catch (Exception ex)
{
// Something went wrong. We don't return this error right away. We want to
// rebuild the expression tree as far as possible for diagnostic purposes.
error = ex;
}
// Start the expression tree with a parameter of type `T`:
var actionParameters = action.GetMethodInfo().GetParameters();
var actionParameterName = actionParameters[actionParameters.Length - 1].Name;
var rootExpression = Expression.Parameter(typeof(T), actionParameterName);
Expression body = rootExpression;
// Then step through one recorded invocation at a time:
for (var recorder = rootRecorder; recorder != null; recorder = recorder.Next)
{
var invocation = recorder.Invocation;
if (invocation != null)
{
body = Expression.Call(body, invocation.Method, GetArgumentExpressions(invocation, recorder.Matches.ToArray()));
}
else
{
// A recorder was set up, but it recorded no invocation. This means
// that the invocation could not be intercepted:
throw new ArgumentException(
string.Format(
CultureInfo.CurrentCulture,
Resources.UnsupportedExpressionWithHint,
$"{actionParameterName} => {body.ToStringFixed()}...",
Resources.NextMemberNonInterceptable));
}
}
// Now we've either got no error and a completely reconstructed expression, or
// we have an error and a partially reconstructed expression which we can use for
// diagnostic purposes:
if (error == null)
{
return(Expression.Lambda <Action <T> >(body.Apply(UpgradePropertyAccessorMethods.Rewriter), rootExpression));
}
else
{
throw new ArgumentException(
string.Format(
CultureInfo.CurrentCulture,
Resources.UnsupportedExpressionWithHint,
$"{actionParameterName} => {body.ToStringFixed()}...",
error.Message));
}
}
Expression[] GetArgumentExpressions(Invocation invocation, Match[] matches)
{
// First, let's pretend that all arguments are constant values:
var parameterTypes = invocation.Method.GetParameterTypes();
var parameterCount = parameterTypes.Count;
var expressions = new Expression[parameterCount];
for (int i = 0; i < parameterCount; ++i)
{
expressions[i] = Expression.Constant(invocation.Arguments[i], parameterTypes[i]);
}
// Now let's override the above constant expressions with argument matchers, if available:
if (matches.Length > 0)
{
int matchIndex = 0;
for (int argumentIndex = 0; matchIndex < matches.Length && argumentIndex < expressions.Length; ++argumentIndex)
{
// We are assuming that by default matchers return `default(T)`. If a matcher was used,
// it will have left behind a `default(T)` argument, possibly coerced to the parameter type.
// Therefore, we attempt to reproduce such coercions using `Convert.ChangeType`:
Type defaultValueType = matches[matchIndex].RenderExpression.Type;
object defaultValue = defaultValueType.GetDefaultValue();
try
{
defaultValue = Convert.ChangeType(defaultValue, parameterTypes[argumentIndex]);
}
catch
{
// Never mind, we tried.
}
if (!object.Equals(invocation.Arguments[argumentIndex], defaultValue))
{
// This parameter has a non-`default` value. We therefore assume that it isn't
// a value that was produced by a matcher. (See explanation in comment above.)
continue;
}
if (parameterTypes[argumentIndex].IsAssignableFrom(defaultValue?.GetType() ?? defaultValueType))
{
// We found a potential match. (Matcher type is assignment-compatible to parameter type.)
if (matchIndex < matches.Length - 1 &&
!(argumentIndex < expressions.Length - 1 || CanDistribute(matchIndex + 1, argumentIndex + 1)))
{
// We get here if there are more matchers to distribute,
// but we either:
// * ran out of parameters to distribute over, or
// * the remaining matchers can't be distributed over the remaining parameters.
// In this case, we bail out, which will lead to an exception being thrown.
break;
}
// The remaining matchers can be distributed over the remaining parameters,
// so we can use up this matcher:
expressions[argumentIndex] = new MatchExpression(matches[matchIndex]);
++matchIndex;
}
}
if (matchIndex < matches.Length)
{
// If we get here, we can be almost certain that matchers weren't distributed properly
// across the invocation's parameters. We could hope for the best and just leave it
// at that; however, it's probably better to let client code know, so it can be either
// adjusted or reported to Moq.
throw new ArgumentException(
string.Format(
CultureInfo.CurrentCulture,
Resources.MatcherAssignmentFailedDuringExpressionReconstruction,
matches.Length,
$"{invocation.Method.DeclaringType.GetFormattedName()}.{invocation.Method.Name}"));
}
bool CanDistribute(int msi, int asi)
{
var match = matches[msi];
var matchType = match.RenderExpression.Type;
for (int ai = asi; ai < expressions.Length; ++ai)
{
if (parameterTypes[ai].IsAssignableFrom(matchType) &&
CanDistribute(msi + 1, ai + 1))
{
return(true);
}
}
return(false);
}
}
// Finally, add explicit type casts (aka `Convert` nodes) where necessary:
for (int i = 0; i < expressions.Length; ++i)
{
var argument = expressions[i];
var parameterType = parameterTypes[i];
if (argument.Type == parameterType)
{
continue;
}
// nullable type coercion:
if (Nullable.GetUnderlyingType(parameterType) != null && Nullable.GetUnderlyingType(argument.Type) == null)
{
expressions[i] = Expression.Convert(argument, parameterType);
}
// boxing of value types (i.e. where a value-typed value is assigned to a reference-typed parameter):
else if (argument.Type.IsValueType && !parameterType.IsValueType)
{
expressions[i] = Expression.Convert(argument, parameterType);
}
// if types don't match exactly and aren't assignment compatible:
else if (argument.Type != parameterType && !parameterType.IsAssignableFrom(argument.Type))
{
expressions[i] = Expression.Convert(argument, parameterType);
}
}
return(expressions);
}
}