/// <summary>
/// Evaluates a string representing a condition from a "condition" attribute.
/// If the condition is a malformed string, it throws an InvalidProjectFileException.
/// This method uses cached expression trees to avoid generating them from scratch every time it's called.
/// This method is thread safe and is called from engine and task execution module threads
/// </summary>
/// <param name="condition">Can be null</param>
/// <param name="conditionAttribute">XML attribute on which the condition is evaluated</param>
/// <param name="expander">All the data available for expanding embedded properties, metadata, and items</param>
/// <param name="conditionedPropertiesTable">Can be null</param>
/// <param name="itemListOptions"></param>
/// <param name="loggingServices">Can be null</param>
/// <param name="buildEventContext"> contains contextual information for logging events</param>
/// <returns>true, if the expression evaluates to true, otherwise false</returns>
internal static bool EvaluateCondition
(
string condition,
XmlAttribute conditionAttribute,
Expander expander,
Hashtable conditionedPropertiesTable,
ParserOptions itemListOptions,
EngineLoggingServices loggingServices,
BuildEventContext buildEventContext
)
{
ErrorUtilities.VerifyThrow((conditionAttribute != null) || (condition.Length == 0),
"If condition is non-empty, you must provide the XML node representing the condition.");
// An empty condition is equivalent to a "true" condition.
if ((null == condition) || (condition.Length == 0))
{
return(true);
}
Hashtable cachedExpressionTreesForCurrentOptions = cachedExpressionTrees[(int)itemListOptions];
// Try and see if we have an expression tree for this condition already
GenericExpressionNode parsedExpression = (GenericExpressionNode)cachedExpressionTreesForCurrentOptions[condition];
if (parsedExpression == null)
{
Parser conditionParser = new Parser();
#region REMOVE_COMPAT_WARNING
conditionParser.LoggingServices = loggingServices;
conditionParser.LogBuildEventContext = buildEventContext;
#endregion
parsedExpression = conditionParser.Parse(condition, conditionAttribute, itemListOptions);
// It's possible two threads will add a different tree to the same entry in the hashtable,
// but it should be rare and it's not a problem - the previous entry will be thrown away.
// We could ensure no dupes with double check locking but it's not really necessary here.
// Also, we don't want to lock on every read.
lock (cachedExpressionTreesForCurrentOptions)
{
cachedExpressionTreesForCurrentOptions[condition] = parsedExpression;
}
}
ConditionEvaluationState state = new ConditionEvaluationState(conditionAttribute, expander, conditionedPropertiesTable, condition);
bool result;
// We are evaluating this expression now and it can cache some state for the duration,
// so we don't want multiple threads working on the same expression
lock (parsedExpression)
{
result = parsedExpression.Evaluate(state);
parsedExpression.ResetState();
}
return(result);
}
/// <summary>
/// If any expression nodes cache any state for the duration of evaluation,
/// now's the time to clean it up
/// </summary>
internal override void ResetState()
{
if (leftChild != null)
{
leftChild.ResetState();
}
if (rightChild != null)
{
rightChild.ResetState();
}
}
/// <summary>
/// If any expression nodes cache any state for the duration of evaluation,
/// now's the time to clean it up
/// </summary>
internal override void ResetState()
{
leftChild?.ResetState();
rightChild?.ResetState();
}
