public override async IAsyncEnumerable <Path> ComputeSelect(EvaluationContext ctx)
{
_listCandidate ??= TemplexBase.Parse(ListExpression);
if (_listCandidate != null)
{
// Expression select
var select = _listCandidate.ComputeSelect(ctx);
await foreach (var atom in select)
{
yield return(atom);
}
// Expression paths
var paths = _listCandidate.ComputePaths(ctx);
await foreach (var path in paths)
{
yield return(path.Append("Id"));
}
// Inner template select
var scopedCtx = ctx.Clone();
scopedCtx.SetLocalVariable(IteratorVariableName, new EvaluationVariable(
eval: TemplateUtil.VariableThatThrows(IteratorVariableName),
selectResolver: () => select,
pathsResolver: () => paths
));
await foreach (var atom in Inner.ComputeSelect(scopedCtx))
{
yield return(atom);
}
}
}
public override async Task GenerateOutputs(EvaluationContext ctx)
{
_listCandidate ??= TemplexBase.Parse(ListExpression);
if (_listCandidate != null)
{
var listObj = (await _listCandidate.Evaluate(ctx)) ?? new List <object>();
if (listObj is IList list)
{
foreach (var listItem in list)
{
// Initialize new evaluation context with the new variable in it
var scopedCtx = ctx.Clone();
scopedCtx.SetLocalVariable(IteratorVariableName, new EvaluationVariable(
evalAsync: () => Task.FromResult(listItem),
selectResolver: () => AsyncUtil.Empty <Path>(), // It doesn't matter when generating output
pathsResolver: () => AsyncUtil.Empty <Path>() // It doesn't matter when generating output
));
// Run the template again on that context
await Inner.GenerateOutputs(scopedCtx);
}
}
else
{
throw new TemplateException($"Expression does not evaluate to a list ({_listCandidate}).");
}
}
}
/// <summary>
/// Clones the <see cref="EvaluationContext"/> and returns a new one that contains the new variable.
/// </summary>
private EvaluationContext GetScopeLocalContext(EvaluationContext ctx)
{
_varExpression ??= TemplexBase.Parse(VariableExpression);
var variable = new EvaluationVariable(
evalAsync: () => _varExpression.Evaluate(ctx),
selectResolver: () => _varExpression.ComputeSelect(ctx),
pathsResolver: () => _varExpression.ComputePaths(ctx));
var ctxClone = ctx.Clone();
ctxClone.SetLocalVariable(VariableName, variable);
return(ctxClone);
}
public override async IAsyncEnumerable <Path> ComputeSelect(EvaluationContext ctx)
{
_conditionCandidate ??= TemplexBase.Parse(ConditionExpression);
if (_conditionCandidate != null && Inner != null)
{
await foreach (var select in _conditionCandidate.ComputeSelect(ctx))
{
yield return(select);
}
await foreach (var select in Inner.ComputeSelect(ctx))
{
yield return(select);
}
}
}
public override async Task GenerateOutputs(EvaluationContext ctx)
{
_conditionCandidate ??= TemplexBase.Parse(ConditionExpression);
if (_conditionCandidate != null && Inner != null)
{
var conditionObj = (await _conditionCandidate.Evaluate(ctx)) ?? false;
if (conditionObj is bool condition)
{
if (condition)
{
await Inner.GenerateOutputs(ctx);
}
}
else
{
throw new TemplateException($"If expression could not be applied. Expression ({_conditionCandidate}) does not evaluate to a true or false.");
}
}
}