Module: References

Defined in:
lib/cfn-model/model/references.rb

Overview

this is a placeholder for anything related to resolving references

not sure if we are going to be able to have a useful generic set of code for references yet… in the meantime pile things up here and hope a pattern becomes clear

Class Method Summary collapse

Class Method Details

.is_security_group_id_external(group_id) ⇒ Object 



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# File 'lib/cfn-model/model/references.rb', line 85

def self.is_security_group_id_external(group_id)
  resolve_security_group_id(group_id).nil?
end

.resolve_map(cfn_model, find_in_map) ⇒ Object

Try to compute the FindInMap against a real Mapping

If anything doesn’t match up - either a syntax error, a missing Mapping, or some other kind Cfn evaluation we don’t understand, just return the call to FindInMap



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# File 'lib/cfn-model/model/references.rb', line 99

def self.resolve_map(cfn_model, find_in_map)
  map_name = find_in_map['Fn::FindInMap'][0]
  top_level_key = find_in_map['Fn::FindInMap'][1]
  second_level_key = find_in_map['Fn::FindInMap'][2]

  map = cfn_model.mappings[map_name]

  return find_in_map if map.nil?

  top_level_resolved = resolve_value(cfn_model, top_level_key)

  return find_in_map if !map.has_key?(top_level_resolved)

  top_level = map[top_level_resolved]
  second_level = top_level[resolve_value(cfn_model, second_level_key)]

  return find_in_map if second_level.nil?

  second_level
end

.resolve_reference(cfn_model, value) ⇒ Object

For a !Ref to another resource.… just returns the !REf For a !Ref to a Parameter, then try to synthesize the value



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# File 'lib/cfn-model/model/references.rb', line 53

def self.resolve_reference(cfn_model, value)
  ref_id = value['Ref']
  if ref_id.is_a? String
    if cfn_model.parameters.has_key?(ref_id)
      return value if cfn_model.parameters[ref_id].synthesized_value.nil?
      return cfn_model.parameters[ref_id].synthesized_value
    else
      return value
    end
  else
    value
  end
end

.resolve_resource_id(reference, attr = nil) ⇒ Object 



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# File 'lib/cfn-model/model/references.rb', line 67

def self.resolve_resource_id(reference, attr = nil)
  return nil if reference.is_a? String

  # an imported value can only yield a literal to an external resource vs. referencing something local
  if !reference['Ref'].nil?
    reference['Ref']
  elsif !reference['Fn::GetAtt'].nil?
    logical_resource_id_from_get_att reference['Fn::GetAtt'], attr
  else
    # anything else will be string manipulation functions
    # which again leads us back to a string which must be an external resource known out of band
    # so don't/can't link it up
    return nil
  end
rescue NoMethodError => e
  raise ParserError, e.inspect
end

.resolve_security_group_id(group_id) ⇒ Object 



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# File 'lib/cfn-model/model/references.rb', line 89

def self.resolve_security_group_id(group_id)
  resolve_resource_id group_id, 'GroupId'
end

.resolve_value(cfn_model, value) ⇒ Object 



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# File 'lib/cfn-model/model/references.rb', line 16

def self.resolve_value(cfn_model, value)
  if value.is_a? Hash
    if value.has_key?('Ref')
      resolve_reference(cfn_model, value)
    elsif value.has_key?('Fn::FindInMap')
      resolve_map(cfn_model, value)
    elsif value.has_key?('Fn::If')
      resolve_if(cfn_model, value)
    elsif value.has_key?('Fn::Sub')
      resolve_sub(cfn_model, value)
    elsif value.has_key?('Fn::GetAZs')
      resolve_getazs(cfn_model, value)
    elsif value.has_key?('Fn::Split')
      resolve_split(cfn_model, value)
    elsif value.has_key?('Fn::Join')
      resolve_join(cfn_model, value)
    elsif value.has_key?('Fn::Base64')
      resolve_base64(cfn_model, value)
    elsif value.has_key?('Fn::Select')
      resolve_select(cfn_model, value)
    elsif unsupported_passthru?(value)
      value
    else # another mapping
      value.map do |k,v|
        [k, resolve_value(cfn_model, v)]
      end.to_h
    end
  elsif value.is_a? Array
    value.map { |item| resolve_value(cfn_model, item) }
  else
    value
  end
end

.unsupported_passthru?(value) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/cfn-model/model/references.rb', line 12

def self.unsupported_passthru?(value)
  value.has_key?('Fn::GetAtt') || value.has_key?('Fn::ImportValue') || value.has_key?('Fn::Transform') || value.has_key?('Fn::Cidr')
end