108 lines
3.8 KiB
Ruby
108 lines
3.8 KiB
Ruby
# frozen_string_literal: true
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require "fiber"
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module ActionView
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# == TODO
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#
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# * Support streaming from child templates, partials and so on.
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# * Rack::Cache needs to support streaming bodies
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class StreamingTemplateRenderer < TemplateRenderer # :nodoc:
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# A valid Rack::Body (i.e. it responds to each).
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# It is initialized with a block that, when called, starts
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# rendering the template.
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class Body # :nodoc:
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def initialize(&start)
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@start = start
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end
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def each(&block)
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begin
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@start.call(block)
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rescue Exception => exception
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log_error(exception)
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block.call ActionView::Base.streaming_completion_on_exception
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end
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self
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end
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private
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# This is the same logging logic as in ShowExceptions middleware.
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def log_error(exception)
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logger = ActionView::Base.logger
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return unless logger
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message = +"\n#{exception.class} (#{exception.message}):\n"
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message << exception.annotated_source_code.to_s if exception.respond_to?(:annotated_source_code)
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message << " " << exception.backtrace.join("\n ")
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logger.fatal("#{message}\n\n")
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end
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end
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# For streaming, instead of rendering a given a template, we return a Body
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# object that responds to each. This object is initialized with a block
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# that knows how to render the template.
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def render_template(view, template, layout_name = nil, locals = {}) # :nodoc:
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return [super.body] unless layout_name && template.supports_streaming?
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locals ||= {}
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layout = layout_name && find_layout(layout_name, locals.keys, [formats.first])
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Body.new do |buffer|
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delayed_render(buffer, template, layout, view, locals)
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end
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end
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private
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def delayed_render(buffer, template, layout, view, locals)
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# Wrap the given buffer in the StreamingBuffer and pass it to the
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# underlying template handler. Now, every time something is concatenated
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# to the buffer, it is not appended to an array, but streamed straight
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# to the client.
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output = ActionView::StreamingBuffer.new(buffer)
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yielder = lambda { |*name| view._layout_for(*name) }
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ActiveSupport::Notifications.instrument(
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"render_template.action_view",
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identifier: template.identifier,
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layout: layout && layout.virtual_path
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) do
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outer_config = I18n.config
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fiber = Fiber.new do
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I18n.config = outer_config
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if layout
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layout.render(view, locals, output, &yielder)
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else
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# If you don't have a layout, just render the thing
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# and concatenate the final result. This is the same
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# as a layout with just <%= yield %>
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output.safe_concat view._layout_for
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end
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end
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# Set the view flow to support streaming. It will be aware
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# when to stop rendering the layout because it needs to search
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# something in the template and vice-versa.
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view.view_flow = StreamingFlow.new(view, fiber)
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# Yo! Start the fiber!
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fiber.resume
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# If the fiber is still alive, it means we need something
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# from the template, so start rendering it. If not, it means
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# the layout exited without requiring anything from the template.
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if fiber.alive?
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content = template.render(view, locals, &yielder)
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# Once rendering the template is done, sets its content in the :layout key.
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view.view_flow.set(:layout, content)
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# In case the layout continues yielding, we need to resume
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# the fiber until all yields are handled.
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fiber.resume while fiber.alive?
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end
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end
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end
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end
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end
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