public override async IAsyncEnumerable <Path> ComputeSelect(EvaluationContext ctx)
{
if (ListCandidate != null && Template != 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 Template.ComputeSelect(scopedCtx))
{
yield return(atom);
}
}
}
public override async Task <object> Evaluate(EvaluationContext ctx)
{
var listCandidate = await ListCandidate.Evaluate(ctx);
if (listCandidate == null)
{
// Template indexer implements null propagation out of the box
return(null);
}
if (listCandidate is IList list)
{
if (Index < 0 || Index >= list.Count)
{
// Template indexer implements null propagation out of the box
return(null);
}
return(list[Index]);
}
else
{
throw new TemplateException($"Indexer '#{Index}' is only valid on model entity lists.");
}
}
public override IAsyncEnumerable <Path> ComputePaths(EvaluationContext ctx)
{
//var result = new List<Path>();
//await foreach (var x in ListCandidate.ComputePaths(ctx))
//{
// result.Add(x);
//}
//foreach (var x in result)
//{
// yield return x;
//}
return(ListCandidate.ComputePaths(ctx));
}
public override async Task GenerateOutput(StringBuilder builder, EvaluationContext ctx, Func <string, string> encodeFunc = null)
{
if (ListCandidate != null && Template != null)
{
var listObj = (await ListCandidate.Evaluate(ctx)) ?? new List <object>();
if (listObj is IList list)
{
int index = 0;
foreach (var listItem in list)
{
// Initialize new evaluation context with the new variable in it
var scopedCtx = ctx.Clone();
scopedCtx.SetLocalVariable(IteratorVariableName, new EvaluationVariable(
evalAsync: () => Task.FromResult(listItem),
selectResolver: () => AsyncUtil.Empty <Path>(), // It doesn't matter when generating output
pathsResolver: () => AsyncUtil.Empty <Path>() // It doesn't matter when generating output
));
// Index, useful for setting line numbers
scopedCtx.SetLocalVariable(IteratorVariableName + "_index", new EvaluationVariable(
evalAsync: () => Task.FromResult <object>(index),
selectResolver: () => AsyncUtil.Empty <Path>(), // It doesn't matter when generating output
pathsResolver: () => AsyncUtil.Empty <Path>() // It doesn't matter when generating output
));
// Run the template again on that context
await Template.GenerateOutput(builder, scopedCtx, encodeFunc);
index++;
}
}
else
{
throw new TemplateException($"Foreach expression could not be applied. Expression ({ListCandidate}) does not evaluate to a list.");
}
}
}
public override IAsyncEnumerable <Path> ComputeSelect(EvaluationContext ctx)
{
return(ListCandidate.ComputeSelect(ctx));
}
