Class: Chef::Property

Inherits:
Object
  • Object
show all
Defined in:
lib/chef/property.rb

Overview

Type and validation information for a property on a resource.

A property named “x” manipulates the “@x” instance variable on a resource. The presence of the variable (`instance_variable_defined?(@x)`) tells whether the variable is defined; it may have any actual value, constrained only by validation.

Properties may have validation, defaults, and coercion, and have full support for lazy values.

See Also:

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(**options) ⇒ Property

Create a new property.



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# File 'lib/chef/property.rb', line 121

def initialize(**options)
  options = options.inject({}) { |memo, (key, value)| memo[key.to_sym] = value; memo }
  @options = options
  options[:name] = options[:name].to_sym if options[:name]
  options[:instance_variable_name] = options[:instance_variable_name].to_sym if options[:instance_variable_name]

  # Replace name_attribute with name_property
  if options.key?(:name_attribute)
    # If we have both name_attribute and name_property and they differ, raise an error
    if options.key?(:name_property)
      raise ArgumentError, "name_attribute and name_property are functionally identical and both cannot be specified on a property at once. Use just one on property #{self}"
    end
    # replace name_property with name_attribute in place
    options = Hash[options.map { |k, v| k == :name_attribute ? [ :name_property, v ] : [ k, v ] }]
    @options = options
  end

  if options.key?(:default) && options.key?(:name_property)
    raise ArgumentError, "A property cannot be both a name_property/name_attribute and have a default value. Use one or the other on property #{self}"
  end

  # Recursively freeze the default if it isn't a lazy value.
  unless default.is_a?(DelayedEvaluator)
    visitor = lambda do |obj|
      case obj
      when Hash
        obj.each_value { |value| visitor.call(value) }
      when Array
        obj.each { |value| visitor.call(value) }
      end
      obj.freeze
    end
    visitor.call(default)
  end

  # Validate the default early, so the user gets a good error message, and
  # cache it so we don't do it again if so
  begin
    # If we can validate it all the way to output, do it.
    @stored_default = input_to_stored_value(nil, default, is_default: true)
  rescue Chef::Exceptions::CannotValidateStaticallyError
    # If the validation is not static (i.e. has procs), we will have to
    # coerce and validate the default each time we run
  end
end

Instance Attribute Details

#optionsObject (readonly)

The options this Property will use for get/set behavior and validation.



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# File 'lib/chef/property.rb', line 585

def options
  @options
end

Class Method Details

.derive(**options) ⇒ Object

Create a reusable property type that can be used in multiple properties in different resources.

Examples:

Property.derive(default: 'hi')


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# File 'lib/chef/property.rb', line 50

def self.derive(**options)
  new(**options)
end

.emit_deprecated_alias(from, to, message, declared_in) ⇒ Object

This is to support #deprecated_property_alias, by emitting an alias and a deprecatation warning when called.



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# File 'lib/chef/property.rb', line 62

def self.emit_deprecated_alias(from, to, message, declared_in)
  declared_in.class_eval <<-EOM, __FILE__, __LINE__ + 1
    def #{from}(value=NOT_PASSED)
      Chef.deprecated(:property, "#{message}")
      #{to}(value)
    end
    def #{from}=(value)
      Chef.deprecated(:property, "#{message}")
      #{to} = value
    end
  EOM
end

Instance Method Details

#call(resource, value = NOT_PASSED) ⇒ Object

Handle the property being called.

The base implementation does the property get-or-set:

“`ruby resource.myprop # get resource.myprop value # set “`

Subclasses may implement this with any arguments they want, as long as the corresponding DSL calls it correctly.



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# File 'lib/chef/property.rb', line 346

def call(resource, value = NOT_PASSED)
  if value == NOT_PASSED
    get(resource)
  else
    set(resource, value)
  end
end

#coerce(resource, value) ⇒ Object

Coerce an input value into canonical form for the property.

After coercion, the value is suitable for storage in the resource. You must validate values after coercion, however.

Does no special handling for lazy values.

Raises:

  • Chef::Exceptions::ValidationFailed If the value is invalid for this property.



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# File 'lib/chef/property.rb', line 489

def coerce(resource, value)
  if options.key?(:coerce)
    # nil is never coerced
    unless value.nil?
      value = exec_in_resource(resource, options[:coerce], value)
    end
  end
  value
end

#declared_inClass

The class this property was defined in.



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# File 'lib/chef/property.rb', line 185

def declared_in
  options[:declared_in]
end

#defaultObject

The raw default value for this resource.

Does not coerce or validate the default. Does not evaluate lazy values.

Defaults to `lazy { name }` if name_property is true; otherwise defaults to `nil`



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# File 'lib/chef/property.rb', line 230

def default
  return options[:default] if options.key?(:default)
  return Chef::DelayedEvaluator.new { name } if name_property?
  nil
end

#default_descriptionString

A desciption of the default value of this property.



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# File 'lib/chef/property.rb', line 241

def default_description
  options[:default_description]
end

#derive(**modified_options) ⇒ Property

Derive a new Property that is just like this one, except with some added or changed options.



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# File 'lib/chef/property.rb', line 533

def derive(**modified_options)
  # Since name_property, name_attribute and default override each other,
  # if you specify one of them in modified_options it overrides anything in
  # the original options.
  options = self.options
  if modified_options.key?(:name_property) ||
      modified_options.key?(:name_attribute) ||
      modified_options.key?(:default)
    options = options.reject { |k, v| k == :name_attribute || k == :name_property || k == :default }
  end
  self.class.new(options.merge(modified_options))
end

#descriptionString

A description of this property.



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# File 'lib/chef/property.rb', line 194

def description
  options[:description]
end

#desired_state?Boolean

Whether this is part of desired state or not.

Defaults to true.



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# File 'lib/chef/property.rb', line 261

def desired_state?
  return true if !options.key?(:desired_state)
  options[:desired_state]
end

#emit_dslObject

Emit the DSL for this property into the resource class (`declared_in`).

Creates a getter and setter for the property.



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# File 'lib/chef/property.rb', line 551

def emit_dsl
  # We don't create the getter/setter if it's a custom property; we will
  # be using the existing getter/setter to manipulate it instead.
  return if !instance_variable_name

  # Properties may override existing properties up the inheritance heirarchy, but
  # properties must not override inherited methods like Object#hash.  When the Resource is
  # placed into the resource collection the ruby Hash object will call the
  # Object#hash method on the resource, and overriding that with a property will cause
  # very confusing results.
  if property_redefines_method?
    resource_name = declared_in.respond_to?(:resource_name) ? declared_in.resource_name : declared_in
    raise ArgumentError, "Property `#{name}` of resource `#{resource_name}` overwrites an existing method. A different name should be used for this property."
  end

  # We prefer this form because the property name won't show up in the
  # stack trace if you use `define_method`.
  declared_in.class_eval <<-EOM, __FILE__, __LINE__ + 1
    def #{name}(value=NOT_PASSED)
      raise "Property `#{name}` of `\#{self}` was incorrectly passed a block. Possible property-resource collision. To call a resource named `#{name}` either rename the property or else use `declare_resource(:#{name}, ...)`" if block_given?
      self.class.properties[#{name.inspect}].call(self, value)
    end
    def #{name}=(value)
      raise "Property `#{name}` of `\#{self}` was incorrectly passed a block. Possible property-resource collision. To call a resource named `#{name}` either rename the property or else use `declare_resource(:#{name}, ...)`" if block_given?
      self.class.properties[#{name.inspect}].set(self, value)
    end
  EOM
end

#explicitly_accepts_nil?(resource) ⇒ Boolean

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Find out whether this type accepts nil explicitly.

A type accepts nil explicitly if “is” allows nil, it validates as nil, and is not simply an empty type.

A type is presumed to accept nil if it does coercion (which must handle nil).

These examples accept nil explicitly: “`ruby property :a, [ String, nil ] property :a, [ String, NilClass ] property :a, [ String, proc { |v| v.nil? } ] “`

This does not (because the “is” doesn't exist or doesn't have nil):

“`ruby property :x, String “`

These do not, even though nil would validate fine (because they do not have “is”):

“`ruby property :a property :a, equal_to: [ 1, 2, 3, nil ] property :a, kind_of: [ String, NilClass ] property :a, respond_to: [ ] property :a, callbacks: { “a” => proc { |v| v.nil? } } “`



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# File 'lib/chef/property.rb', line 625

def explicitly_accepts_nil?(resource)
  options.key?(:coerce) ||
    (options.key?(:is) && Chef::Mixin::ParamsValidate.send(:_pv_is, { name => nil }, name, options[:is]))
rescue Chef::Exceptions::ValidationFailed, Chef::Exceptions::CannotValidateStaticallyError
  false
end

#get(resource, nil_set: false) ⇒ Object

Get the property value from the resource, handling lazy values, defaults, and validation.

  • If the property's value is lazy, it is evaluated, coerced and validated.

  • If the property has no value, and is required, raises ValidationFailed.

  • If the property has no value, but has a lazy default, it is evaluated, coerced and validated. If the evaluated value is frozen, the resulting

  • If the property has no value, but has a default, the default value will be returned and frozen. If the default value is lazy, it will be evaluated, coerced and validated, and the result stored in the property.

  • If the property has no value, but is name_property, `resource.name` is retrieved, coerced, validated and stored in the property.

  • Otherwise, `nil` is returned.

Raises:

  • Chef::Exceptions::ValidationFailed If the value is invalid for this property, or if the value is required and not set.



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# File 'lib/chef/property.rb', line 376

def get(resource, nil_set: false)
  # If it's set, return it (and evaluate any lazy values)
  value = nil

  if is_set?(resource)
    value = get_value(resource)
    value = stored_value_to_output(resource, value)
  else
    # We are getting the default value.

    if has_default?
      # If we were able to cache the stored_default, grab it.
      if defined?(@stored_default)
        value = @stored_default
      else
        # Otherwise, we have to validate it now.
        value = input_to_stored_value(resource, default, is_default: true)
      end
      value = stored_value_to_output(resource, value)

      # If the value is mutable (non-frozen), we set it on the instance
      # so that people can mutate it.  (All constant default values are
      # frozen.)
      if !value.frozen? && !value.nil?
        set_value(resource, value)
      end
    end
  end

  if value.nil? && required?
    raise Chef::Exceptions::ValidationFailed, "#{name} is a required property"
  else
    value
  end
end

#get_value(resource) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.



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# File 'lib/chef/property.rb', line 633

def get_value(resource)
  if instance_variable_name
    resource.instance_variable_get(instance_variable_name)
  else
    resource.send(name)
  end
end

#has_default?Boolean

Whether this property has a default value.



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# File 'lib/chef/property.rb', line 280

def has_default?
  options.key?(:default) || name_property?
end

#identity?Boolean

Whether this is part of the resource's natural identity or not.



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# File 'lib/chef/property.rb', line 250

def identity?
  options[:identity]
end

#instance_variable_nameSymbol

The instance variable associated with this property.

Defaults to `@<name>`



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# File 'lib/chef/property.rb', line 214

def instance_variable_name
  if options.key?(:instance_variable_name)
    options[:instance_variable_name]
  elsif name
    :"@#{name}"
  end
end

#introducedString

When this property was introduced



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# File 'lib/chef/property.rb', line 203

def introduced
  options[:introduced]
end

#is_set?(resource) ⇒ Boolean

Find out whether this property has been set.

This will be true if:

  • The user explicitly set the value

  • The property has a default, and the value was retrieved.

From this point of view, it is worth looking at this as “what does the user think this value should be.” In order words, if the user grabbed the value, even if it was a default, they probably based calculations on it. If they based calculations on it and the value changes, the rest of the world gets inconsistent.



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# File 'lib/chef/property.rb', line 458

def is_set?(resource)
  value_is_set?(resource)
end

#nameString

The name of this property.



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# File 'lib/chef/property.rb', line 176

def name
  options[:name]
end

#name_property?Boolean

Whether this is name_property or not.



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# File 'lib/chef/property.rb', line 271

def name_property?
  options[:name_property]
end

#required?Boolean

Whether this property is required or not.



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# File 'lib/chef/property.rb', line 289

def required?
  options[:required]
end

#reset(resource) ⇒ Object

Reset the value of this property so that is_set? will return false and the default will be returned in the future.



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# File 'lib/chef/property.rb', line 468

def reset(resource)
  reset_value(resource)
end

#reset_value(resource) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.



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# File 'lib/chef/property.rb', line 660

def reset_value(resource)
  if instance_variable_name
    if value_is_set?(resource)
      resource.remove_instance_variable(instance_variable_name)
    end
  else
    raise ArgumentError, "Property #{name} has no instance variable defined and cannot be reset"
  end
end

#sensitive?Boolean

Whether this property is sensitive or not.

Defaults to false.



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# File 'lib/chef/property.rb', line 311

def sensitive?
  options.fetch(:sensitive, false)
end

#set(resource, value) ⇒ Object

Set the value of this property in the given resource.

Non-lazy values are coerced and validated before being set. Coercion and validation of lazy values is delayed until they are first retrieved.

Raises:

  • Chef::Exceptions::ValidationFailed If the value is invalid for this property.



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# File 'lib/chef/property.rb', line 427

def set(resource, value)
  value = set_value(resource, input_to_stored_value(resource, value))

  if options.key?(:deprecated)
    Chef.deprecated(:property, options[:deprecated])
  end

  if value.nil? && required?
    raise Chef::Exceptions::ValidationFailed, "#{name} is a required property"
  else
    value
  end
end

#set_value(resource, value) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.



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# File 'lib/chef/property.rb', line 642

def set_value(resource, value)
  if instance_variable_name
    resource.instance_variable_set(instance_variable_name, value)
  else
    resource.send(name, value)
  end
end

#skip_docs?Boolean

Whether this property should be skipped for documentation purposes.

Defaults to false.



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# File 'lib/chef/property.rb', line 300

def skip_docs?
  options.fetch(:skip_docs, false)
end

#to_sObject



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# File 'lib/chef/property.rb', line 167

def to_s
  "#{name || "<property type>"}#{declared_in ? " of resource #{declared_in.resource_name}" : ""}"
end

#validate(resource, value) ⇒ Object

Validate a value.

Calls Chef::Mixin::ParamsValidate#validate with #validation_options as options.

Raises:

  • Chef::Exceptions::ValidationFailed If the value is invalid for this property.



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# File 'lib/chef/property.rb', line 512

def validate(resource, value)
  # nils are not validated unless we have an explicit default value
  if !value.nil? || has_default?
    if resource
      resource.validate({ name => value }, { name => validation_options })
    else
      name = self.name || :property_type
      Chef::Mixin::ParamsValidate.validate({ name => value }, { name => validation_options })
    end
  end
end

#validation_optionsHash<Symbol,Object>

Validation options. (See Chef::Mixin::ParamsValidate#validate.)



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# File 'lib/chef/property.rb', line 320

def validation_options
  @validation_options ||= options.reject do |k, v|
    [:declared_in, :name, :instance_variable_name, :desired_state, :identity, :default, :name_property, :coerce, :required, :nillable, :sensitive, :description, :introduced, :deprecated, :default_description, :skip_docs].include?(k)
  end
end

#value_is_set?(resource) ⇒ Boolean

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.



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# File 'lib/chef/property.rb', line 651

def value_is_set?(resource)
  if instance_variable_name
    resource.instance_variable_defined?(instance_variable_name)
  else
    true
  end
end