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Diffstat (limited to 'lib/chef/property.rb')
| -rw-r--r-- | lib/chef/property.rb | 539 |
1 files changed, 539 insertions, 0 deletions
diff --git a/lib/chef/property.rb b/lib/chef/property.rb new file mode 100644 index 0000000000..408090d37b --- /dev/null +++ b/lib/chef/property.rb @@ -0,0 +1,539 @@ +# +# Author:: John Keiser <jkeiser@chef.io> +# Copyright:: Copyright (c) 2015 John Keiser. +# License:: Apache License, Version 2.0 +# +# Licensed under the Apache License, Version 2.0 (the "License"); +# you may not use this file except in compliance with the License. +# You may obtain a copy of the License at +# +# http://www.apache.org/licenses/LICENSE-2.0 +# +# Unless required by applicable law or agreed to in writing, software +# distributed under the License is distributed on an "AS IS" BASIS, +# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +# See the License for the specific language governing permissions and +# limitations under the License. +# + +require 'chef/exceptions' +require 'chef/delayed_evaluator' + +class Chef + # + # 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 Chef::Resource.property + # @see Chef::DelayedEvaluator + # + class Property + # + # Create a reusable property type that can be used in multiple properties + # in different resources. + # + # @param options [Hash<Symbol,Object>] Validation options. See Chef::Resource.property for + # the list of options. + # + # @example + # Property.derive(default: 'hi') + # + def self.derive(**options) + new(**options) + end + + # + # Create a new property. + # + # @param options [Hash<Symbol,Object>] Property options, including + # control options here, as well as validation options (see + # Chef::Mixin::ParamsValidate#validate for a description of validation + # options). + # @option options [Symbol] :name The name of this property. + # @option options [Class] :declared_in The class this property comes from. + # @option options [Symbol] :instance_variable_name The instance variable + # tied to this property. Must include a leading `@`. Defaults to `@<name>`. + # `nil` means the property is opaque and not tied to a specific instance + # variable. + # @option options [Boolean] :desired_state `true` if this property is part of desired + # state. Defaults to `true`. + # @option options [Boolean] :identity `true` if this property is part of object + # identity. Defaults to `false`. + # @option options [Boolean] :name_property `true` if this + # property defaults to the same value as `name`. Equivalent to + # `default: lazy { name }`, except that #property_is_set? will + # return `true` if the property is set *or* if `name` is set. + # @option options [Object] :default The value this property + # will return if the user does not set one. If this is `lazy`, it will + # be run in the context of the instance (and able to access other + # properties) and cached. If not, the value will be frozen with Object#freeze + # to prevent users from modifying it in an instance. + # @option options [Proc] :coerce A proc which will be called to + # transform the user input to canonical form. The value is passed in, + # and the transformed value returned as output. Lazy values will *not* + # be passed to this method until after they are evaluated. Called in the + # context of the resource (meaning you can access other properties). + # @option options [Boolean] :required `true` if this property + # must be present; `false` otherwise. This is checked after the resource + # is fully initialized. + # + def initialize(**options) + options.each { |k,v| options[k.to_sym] = v if k.is_a?(String) } + options[:name_property] = options.delete(:name_attribute) unless options.has_key?(:name_property) + @options = options + + if options.has_key?(:default) + options[:default] = options[:default].freeze + end + options[:name] = options[:name].to_sym if options[:name] + options[:instance_variable_name] = options[:instance_variable_name].to_sym if options[:instance_variable_name] + end + + # + # The name of this property. + # + # @return [String] + # + def name + options[:name] + end + + # + # The class this property was defined in. + # + # @return [Class] + # + def declared_in + options[:declared_in] + end + + # + # The instance variable associated with this property. + # + # Defaults to `@<name>` + # + # @return [Symbol] + # + def instance_variable_name + if options.has_key?(:instance_variable_name) + options[:instance_variable_name] + elsif name + :"@#{name}" + end + end + + # + # 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` + # + def default + return options[:default] if options.has_key?(:default) + return Chef::DelayedEvaluator.new { name } if name_property? + nil + end + + # + # Whether this is part of the resource's natural identity or not. + # + # @return [Boolean] + # + def identity? + options[:identity] + end + + # + # Whether this is part of desired state or not. + # + # Defaults to true. + # + # @return [Boolean] + # + def desired_state? + return true if !options.has_key?(:desired_state) + options[:desired_state] + end + + # + # Whether this is name_property or not. + # + # @return [Boolean] + # + def name_property? + options[:name_property] + end + + # + # Whether this property has a default value. + # + # @return [Boolean] + # + def has_default? + options.has_key?(:default) || name_property? + end + + # + # Whether this property is required or not. + # + # @return [Boolean] + # + def required? + options[:required] + end + + # + # Validation options. (See Chef::Mixin::ParamsValidate#validate.) + # + # @return [Hash<Symbol,Object>] + # + def validation_options + @validation_options ||= options.reject { |k,v| + [:declared_in,:name,:instance_variable_name,:desired_state,:identity,:default,:name_property,:coerce,:required].include?(k) + } + end + + # + # 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. + # + # @param resource [Chef::Resource] The resource to get the property from. + # @param value The value to set (or NOT_PASSED if it is a get). + # + # @return The current value of the property. If it is a `set`, lazy values + # will be returned without running, validating or coercing. If it is a + # `get`, the non-lazy, coerced, validated value will always be returned. + # + def call(resource, value=NOT_PASSED) + if value == NOT_PASSED + return get(resource) + end + + # myprop nil is sometimes a get (backcompat) + if value.nil? && !explicitly_accepts_nil?(resource) + # If you say "my_property nil" and the property explicitly accepts + # nil values, we consider this a get. + Chef::Log.deprecation("#{name} nil currently does not overwrite the value of #{name}. This will change in Chef 13, and the value will be set to nil instead. Please change your code to explicitly accept nil using \"property :#{name}, [MyType, nil]\", or stop setting this value to nil.") + return get(resource) + end + + # Anything else (myprop value) is a set + set(resource, value) + end + + # + # 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. + # + # @param resource [Chef::Resource] The resource to get the property from. + # + # @return The value of the property. + # + # @raise Chef::Exceptions::ValidationFailed If the value is invalid for + # this property, or if the value is required and not set. + # + def get(resource) + if is_set?(resource) + value = get_value(resource) + if value.is_a?(DelayedEvaluator) + value = exec_in_resource(resource, value) + value = coerce(resource, value) + validate(resource, value) + end + value + + else + if has_default? + value = default + if value.is_a?(DelayedEvaluator) + value = exec_in_resource(resource, value) + end + + value = coerce(resource, value) + + # We don't validate defaults + + # 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? + set_value(resource, value) + end + + value + + elsif required? + raise Chef::Exceptions::ValidationFailed, "#{name} is required" + end + end + end + + # + # 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. + # + # @param resource [Chef::Resource] The resource to set this property in. + # @param value The value to set. + # + # @return The value that was set, after coercion (if lazy, still returns + # the lazy value) + # + # @raise Chef::Exceptions::ValidationFailed If the value is invalid for + # this property. + # + def set(resource, value) + unless value.is_a?(DelayedEvaluator) + value = coerce(resource, value) + validate(resource, value) + end + set_value(resource, value) + end + + # + # 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. + # + # @param resource [Chef::Resource] The resource to get the property from. + # + # @return [Boolean] + # + def is_set?(resource) + value_is_set?(resource) + end + + # + # Reset the value of this property so that is_set? will return false and the + # default will be returned in the future. + # + # @param resource [Chef::Resource] The resource to get the property from. + # + def reset(resource) + reset_value(resource) + end + + # + # 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. + # + # @param resource [Chef::Resource] The resource we're coercing against + # (to provide context for the coerce). + # @param value The value to coerce. + # + # @return The coerced value. + # + # @raise Chef::Exceptions::ValidationFailed If the value is invalid for + # this property. + # + def coerce(resource, value) + if options.has_key?(:coerce) + value = exec_in_resource(resource, options[:coerce], value) + end + value + end + + # + # Validate a value. + # + # Calls Chef::Mixin::ParamsValidate#validate with #validation_options as + # options. + # + # @param resource [Chef::Resource] The resource we're validating against + # (to provide context for the validate). + # @param value The value to validate. + # + # @raise Chef::Exceptions::ValidationFailed If the value is invalid for + # this property. + # + def validate(resource, value) + resource.validate({ name => value }, { name => validation_options }) + end + + # + # Derive a new Property that is just like this one, except with some added or + # changed options. + # + # @param options [Hash<Symbol,Object>] List of options that would be passed + # to #initialize. + # + # @return [Property] The new property type. + # + def derive(**modified_options) + Property.new(**options.merge(**modified_options)) + end + + # + # Emit the DSL for this property into the resource class (`declared_in`). + # + # Creates a getter and setter for the property. + # + 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 + + # 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) + self.class.properties[#{name.inspect}].call(self, value) + end + def #{name}=(value) + self.class.properties[#{name.inspect}].set(self, value) + end + EOM + rescue SyntaxError + # If the name is not a valid ruby name, we use define_method. + resource_class.define_method(name) do |value=NOT_PASSED| + self.class.properties[name].call(self, value) + end + resource_class.define_method("#{name}=") do |value| + self.class.properties[name].set(self, value) + end + end + + protected + + # + # The options this Property will use for get/set behavior and validation. + # + # @see #initialize for a list of valid options. + # + attr_reader :options + + # + # 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. + # + # 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? } } + # ``` + # + # @param resource [Chef::Resource] The resource we're coercing against + # (to provide context for the coerce). + # + # @return [Boolean] Whether this value explicitly accepts nil. + # + # @api private + def explicitly_accepts_nil?(resource) + options.has_key?(:is) && resource.send(:_pv_is, { name => nil }, name, options[:is], raise_error: false) + end + + def get_value(resource) + if instance_variable_name + resource.instance_variable_get(instance_variable_name) + else + resource.send(name) + end + end + + def set_value(resource, value) + if instance_variable_name + resource.instance_variable_set(instance_variable_name, value) + else + resource.send(name, value) + end + end + + def value_is_set?(resource) + if instance_variable_name + resource.instance_variable_defined?(instance_variable_name) + else + true + end + end + + 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 + + def exec_in_resource(resource, proc, *args) + if resource + if proc.arity > args.size + value = proc.call(resource, *args) + else + value = resource.instance_exec(*args, &proc) + end + else + value = proc.call + end + + if value.is_a?(DelayedEvaluator) + value = coerce(resource, value) + validate(resource, value) + end + value + end + end +end |