set context's template_name with template's name

[ggmichaelgo]

Problem

When Liquid is used with a FileSystem that allows render and include tags to render a file just by its filename, the error message does not show its actual file path.

setup:

# index.liquid
{% render 'foo' with errors %}

# /some/path/snippets/foo.liquid
{{ foo.standard_error }}

output:

Liquid error (foo line 1): standard error

This becomes an issue when Liquid developers have duplicate filenames in multiple folders, which creates confusion where the error is actually coming from.

Solution

In render and include tag, it will set the context.template with template.name.
The Liquid users can use TemplateFactory to create a Template with a name:

class TemplateFactory
  def for(template_name)
    template = Liquid::Template.new
    template.name = "snippets/" + template_name
    template
  end
end

context = Liquid::Context.build(
  registers: { template_factory: StubTemplateFactory.new }
)

template = Liquid::Template.parse("....", line_numbers: true)
template.render(context)

# renders error message in a format of `Liquid error ({folder}/{filename} line #): error message`
Liquid error (snippets/foo line 1): standard error

[dylanahsmith]

When Liquid is used with a FileSystem that allows render and include tags to render a file just by its filename, the error message does not show its actual file path.

This is by design, since we wouldn't want to leak the full file path. Liquid is designed to allow users to design the page without given those users full system access, meaning that we do want to limit the path to the subpath that the user has access to.

This becomes an issue when Liquid developers have duplicate filenames in multiple folders, which creates confusion where the error is actually coming from.

Liquid doesn't have the concept of multiple folders, but in practice the partials can end up in a different directory than the template. Once a layout template is introduced, which may be in another folder, then this can easily introduce confusion. As such, it makes sense to have the template name to include the subpath from the root of the directory that the user stores liquid code in. E.g. if they stored their code in a github repo, it could give the path from the root of that repo, as opposed to the subpath for the partials/snippets.

[dylanahsmith]

I think the .delete_suffix('.liquid') part could be handled in the file system itself.

Also, it would be preferable for this to be cached as part of the PartialCache.load. In fact, it would be more natural to give the Liquid::Template an attr_accessor :name, which could be set when loading the template from a template factory. PartialCache.load could then set template.name ||= template_name to preserve this existing behaviour.

[dylanahsmith]

The other reason having a Template#name property would be useful is that it could be used as part of given a name to the initial template. I think we could provide that as a parse option, then Template#render can set context.template_name = template.name if template.name. I think that would make it easy to set the top-level template name so that it can be included in error messages.

[dylanahsmith]

I think the partial.name can be set in the template factory in applications that want to customize this. That way this can just set the default

Suggested change

	partial.name ||= if context.registers[:file_system]&.respond_to?(:actual_template_name)
	context.registers[:file_system].actual_template_name(template_name)
	else
	template_name
	end
	partial.name ||= template_name

[dylanahsmith]

I think this can be set unconditionally. The reason why I was saying to make it conditional in Template#render (if we support a template name parse argument) is to preserve the behaviour of any application that sets Context#template_name on the passed in Context.

Suggested change

	context.template_name = partial.name if partial.name
	context.template_name = partial.name

[dylanahsmith]

Suggested change

	inner_context.template_name = partial.name if partial.name
	inner_context.template_name = partial.name