Class: Rattler::Parsers::Fail

Inherits:
Parser show all
Defined in:
lib/rattler/parsers/fail.rb

Overview

Fail is a parser that always fails. It can be used to define more useful error messages.

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Parser

#&, #>>, #capturing_decidable?, #labeled?, #list, #one_or_more, #optional, #repeat, #semantic?, #sequence?, #skip, #variable_capture_count?, #with_ws, #zero_or_more, #|

Methods included from Runtime::ParserHelper

#select_captures

Methods inherited from Util::Node

#==, #[], #attrs, #can_equal?, #child, #children, #each, #empty?, #eql?, #initialize, #inspect, #method_missing, #name, #pretty_print, #pretty_print_cycle, #respond_to?, #same_contents?, #to_graphviz, #with_attrs, #with_attrs!, #with_children

Constructor Details

This class inherits a constructor from Rattler::Util::Node

Dynamic Method Handling

This class handles dynamic methods through the method_missing method in the class Rattler::Util::Node

Class Method Details

.[](type, message) ⇒ Fail

Create a new parser that always fails with message. The type should be one of :expr, :rule or :parse, indicating to simply fail, to cause its parse rule to fail, or to cause the entire parse to fail, respectively.

Parameters:

  • type (Symbol) —

    :expr, :rule or :parse

Returns:

  • (Fail) —

    a new parser that always fails with message



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# File 'lib/rattler/parsers/fail.rb', line 29

def self.[](type, message)
  self.new(:type => type, :message => message)
end

.parsed(results, *_) ⇒ Object 



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# File 'lib/rattler/parsers/fail.rb', line 10

def self.parsed(results, *_) #:nodoc:
  keyword, arg_expr = results
  arg = eval(arg_expr)
  case keyword
  when 'fail'       then self[:expr, arg]
  when 'fail_rule'  then self[:rule, arg]
  when 'fail_parse' then self[:parse, arg]
  when 'expected'   then self[:expr, arg.to_sym]
  end
end

Instance Method Details

#capturing? ⇒ Boolean

Returns false.

Returns:

  • (Boolean) —

    false



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# File 'lib/rattler/parsers/fail.rb', line 46

def capturing?
  false
end

#parse(*_) ⇒ Object

Always return false. The parser code generated for this parser should use message as the failure message, and should cause its parse rule to fail if type is :rule or cause the entire parse to fail if type is :parse

Parameters:

  • scanner (StringScanner) —

    the scanner for the current parse

  • rules (RuleSet) —

    the grammar rules being used for the current parse

  • scope (ParserScope) —

    the scope of captured results

Returns:

  • false



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# File 'lib/rattler/parsers/fail.rb', line 41

def parse(*_)
  false
end