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module Parslet
module ErrorReporter
# An error reporter has two central methods, one for reporting errors at
# the current parse position (#err) and one for reporting errors at a
# given parse position (#err_at). The reporter can return an object (a
# 'cause') that will be returned to the caller along with the information
# that the parse failed.
#
# When reporting errors on the outer levels of your parser, these methods
# get passed a list of error objects ('causes') from the inner levels. In
# this default implementation, the inner levels are considered error
# subtrees and are appended to the generated tree node at each level,
# thereby constructing an error tree.
#
# This error tree will report in parallel with the grammar structure that
# failed. A one-to-one correspondence exists between each error in the
# tree and the parslet atom that produced that error.
#
# The implementor is really free to use these return values as he sees
# fit. One example would be to return an error state object from these
# methods that is then updated as errors cascade up the parse derivation
# tree.
#
class Tree
# Produces an error cause that combines the message at the current level
# with the errors that happened at a level below (children).
#
# @param atom [Parslet::Atoms::Base] parslet that failed
# @param source [Source] Source that we're using for this parse. (line
# number information...)
# @param message [String, Array] Error message at this level.
# @param children [Array] A list of errors from a deeper level (or nil).
# @return [Cause] An error tree combining children with message.
#
def err(atom, source, message, children=nil)
position = source.pos
Cause.format(source, position, message, children)
end
# Produces an error cause that combines the message at the current level
# with the errors that happened at a level below (children).
#
# @param atom [Parslet::Atoms::Base] parslet that failed
# @param source [Source] Source that we're using for this parse. (line
# number information...)
# @param message [String, Array] Error message at this level.
# @param pos [Fixnum] The real position of the error.
# @param children [Array] A list of errors from a deeper level (or nil).
# @return [Cause] An error tree combining children with message.
#
def err_at(atom, source, message, pos, children=nil)
position = pos
Cause.format(source, position, message, children)
end
end
end
end
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