42 lines
1.2 KiB
Ruby
42 lines
1.2 KiB
Ruby
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# This wraps pieces of parslet definition and gives them a name. The wrapped
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# piece is lazily evaluated and cached. This has two purposes:
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#
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# * Avoid infinite recursion during evaluation of the definition
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# * Be able to print things by their name, not by their sometimes
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# complicated content.
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#
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# You don't normally use this directly, instead you should generated it by
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# using the structuring method Parslet.rule.
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#
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class Parslet::Atoms::Entity < Parslet::Atoms::Base
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attr_reader :name, :block
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def initialize(name, &block)
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super()
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@name = name
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@block = block
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end
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def try(source, context, consume_all)
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parslet.apply(source, context, consume_all)
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end
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def parslet
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@parslet ||= @block.call.tap { |p|
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raise_not_implemented unless p
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}
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end
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def to_s_inner(prec)
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name.to_s.upcase
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end
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private
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def raise_not_implemented
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trace = caller.reject {|l| l =~ %r{#{Regexp.escape(__FILE__)}}} # blatantly stolen from dependencies.rb in activesupport
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exception = NotImplementedError.new("rule(#{name.inspect}) { ... } returns nil. Still not implemented, but already used?")
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exception.set_backtrace(trace)
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raise exception
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end
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end
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