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);
}
}
}
/// <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);
}