public override async IAsyncEnumerable <Path> ComputeSelect(EvaluationContext ctx)
{
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 TemplateVariable(
eval: TemplateUtil.VariableThatThrows(IteratorVariableName),
selectResolver: () => select,
pathsResolver: () => paths
));
await foreach (var atom in Template.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)
{
TemplateVariable variable;
if (Value == null)
{
variable = new TemplateVariable(
value: null,
selectResolver: () => Value.ComputeSelect(ctx),
pathsResolver: () => Value.ComputePaths(ctx));
}
else
{
variable = new TemplateVariable(
evalAsync: () => Value.Evaluate(ctx),
selectResolver: () => Value.ComputeSelect(ctx),
pathsResolver: () => Value.ComputePaths(ctx));
}
var clone = ctx.Clone();
clone.SetLocalVariable(VariableName, variable);
return(clone);
}
public override async Task GenerateOutput(StringBuilder builder, EvaluationContext ctx, Func <string, string> encodeFunc = null)
{
if (ListCandidate != 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 TemplateVariable(
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 TemplateVariable(
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");
}
}
}