Refactor template loading mechanism

[thekid]

Instead of throwing an exception when load() is called, an Input instance is returned. Its exists() method can be used to test whether the loaded template exists.

Old code

Needs to use exceptions for flow control...

$previous= $templates->register('@partial-block', $this->fn);
try {
  return $context->engine->transform($this->name, $context, $this->start, $this->end, '');
} catch (TemplateNotFoundException $e) {
  return $this->fn->evaluate($context);
} finally {
  $templates->register('@partial-block', $previouss);
}

New code

Longer but can use exists() to check for templates

$source= $templates->source($this->name);
if ($source->exists()) {
  $previous= $templates->register('@partial-block', $this->fn);
  try {
    return $context->engine->render($source, $context, $this->start, $this->end, '');
  } finally {
    $templates->register('@partial-block', $previous);
  }
} else {
  return $this->fn->evaluate($context);
}

See xp-forge/handlebars#9 (review)

[thekid]

This was dropped, use evaluate() if necessary.

[thekid]

The WithListing interface should be merged into the Templates class.

[thekid]

This is unfortunately not backwards compatible as the template loaders have changed type, and passing them to a method with type hint yields:

Argument 1 passed to com\handlebarsjs\HandlebarsEngine::withTemplates() must be an instance of com\github\mustache\TemplateLoader, instance of com\github\mustache\InMemory given

[thekid]

This could also be:

$source= new Tokens('<string>', new StringTokenizer($source));
return $source->compile($this->parser, $start, $end, $indent); 

...but the inlined version saves us a couple of nanoseconds here:)

[thekid]

Released in https://github.com/xp-forge/mustache/releases/tag/v5.1.0