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serialization.cr
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serialization.cr
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module YAML
annotation Field
end
# The `YAML::Serializable` module automatically generates methods for YAML serialization when included.
#
# ### Example
#
# ```
# require "yaml"
#
# class Location
# include YAML::Serializable
#
# @[YAML::Field(key: "lat")]
# property latitude : Float64
#
# @[YAML::Field(key: "lng")]
# property longitude : Float64
# end
#
# class House
# include YAML::Serializable
# property address : String
# property location : Location?
# end
#
# house = House.from_yaml(%({"address": "Crystal Road 1234", "location": {"lat": 12.3, "lng": 34.5}}))
# house.address # => "Crystal Road 1234"
# house.location # => #<Location:0x10cd93d80 @latitude=12.3, @longitude=34.5>
# house.to_yaml # => "---\naddress: Crystal Road 1234\nlocation:\n lat: 12.3\n lng: 34.5\n"
#
# houses = Array(House).from_yaml("---\n- address: Crystal Road 1234\n location:\n lat: 12.3\n lng: 34.5\n")
# houses.size # => 1
# houses.to_yaml # => "---\n- address: Crystal Road 1234\n location:\n lat: 12.3\n lng: 34.5\n"
# ```
#
# ### Usage
#
# Including `YAML::Serializable` will create `#to_yaml` and `self.from_yaml` methods on the current class,
# and a constructor which takes a `YAML::PullParser`. By default, these methods serialize into a yaml
# object containing the value of every instance variable, the keys being the instance variable name.
# Most primitives and collections supported as instance variable values (string, integer, array, hash, etc.),
# along with objects which define to_yaml and a constructor taking a `YAML::PullParser`.
# Union types are also supported, including unions with nil. If multiple types in a union parse correctly,
# it is undefined which one will be chosen.
#
# To change how individual instance variables are parsed and serialized, the annotation `YAML::Field`
# can be placed on the instance variable. Annotating property, getter and setter macros is also allowed.
# ```
# class A
# include YAML::Serializable
#
# @[YAML::Field(key: "my_key", emit_null: true)]
# getter a : Int32?
# end
# ```
#
# `YAML::Field` properties:
# * **ignore**: if `true` skip this field in seriazation and deserialization (by default false)
# * **key**: the value of the key in the yaml object (by default the name of the instance variable)
# * **converter**: specify an alternate type for parsing and generation. The converter must define `from_yaml(YAML::PullParser)` and `to_yaml(value, YAML::Builder)` as class methods. Examples of converters are `Time::Format` and `Time::EpochConverter` for `Time`.
# * **presence**: if `true`, a `@{{key}}_present` instance variable will be generated when the key was present (even if it has a `null` value), `false` by default
# * **emit_null**: if `true`, emits a `null` value for nilable property (by default nulls are not emitted)
#
# Deserialization also respects default values of variables:
# ```
# struct A
# include YAML::Serializable
# @a : Int32
# @b : Float64 = 1.0
# end
#
# A.from_yaml("---\na: 1\n") # => A(@a=1, @b=1.0)
# ```
#
# ### Extensions: `YAML::Serializable::Strict` and `YAML::Serializable::Unmapped`.
#
# If the `YAML::Serializable::Strict` module is included, unknown properties in the YAML
# document will raise a parse exception. By default the unknown properties
# are silently ignored.
# If the `YAML::Serializable::Unmapped` module is included, unknown properties in the YAML
# document will be stored in a `Hash(String, YAML::Any)`. On serialization, any keys inside yaml_unmapped
# will be serialized appended to the current yaml object.
# ```
# struct A
# include YAML::Serializable
# include YAML::Serializable::Unmapped
# @a : Int32
# end
#
# a = A.from_yaml("---\na: 1\nb: 2\n") # => A(@yaml_unmapped={"b" => 2_i64}, @a=1)
# a.to_yaml # => "---\na: 1\nb: 2\n"
# ```
#
#
# ### Class annotation `YAML::Serializable::Options`
#
# supported properties:
# * **emit_nulls**: if `true`, emits a `null` value for all nilable properties (by default nulls are not emitted)
#
# ```
# @[YAML::Serializable::Options(emit_nulls: true)]
# class A
# include YAML::Serializable
# @a : Int32?
# end
# ```
module Serializable
annotation Options
end
macro included
# Define a `new` directly in the included type,
# so it overloads well with other possible initializes
def self.new(ctx : YAML::ParseContext, node : YAML::Nodes::Node)
ctx.read_alias(node, \{{@type}}) do |obj|
return obj
end
instance = allocate
ctx.record_anchor(node, instance)
instance.initialize(__context_for_yaml_serializable: ctx, __node_for_yaml_serializable: node)
GC.add_finalizer(instance) if instance.responds_to?(:finalize)
instance
end
# When the type is inherited, carry over the `new`
# so it can compete with other possible intializes
macro inherited
def self.new(ctx : YAML::ParseContext, node : YAML::Nodes::Node)
super
end
end
end
def initialize(*, __context_for_yaml_serializable ctx : YAML::ParseContext, __node_for_yaml_serializable node : ::YAML::Nodes::Node)
{% begin %}
{% properties = {} of Nil => Nil %}
{% for ivar in @type.instance_vars %}
{% ann = ivar.annotation(::YAML::Field) %}
{% unless ann && ann[:ignore] %}
{%
properties[ivar.id] = {
type: ivar.type,
key: ((ann && ann[:key]) || ivar).id.stringify,
has_default: ivar.has_default_value?,
default: ivar.default_value,
nilable: ivar.type.nilable?,
converter: ann && ann[:converter],
presence: ann && ann[:presence],
}
%}
{% end %}
{% end %}
{% for name, value in properties %}
%var{name} = nil
%found{name} = false
{% end %}
case node
when YAML::Nodes::Mapping
YAML::Schema::Core.each(node) do |key_node, value_node|
unless key_node.is_a?(YAML::Nodes::Scalar)
key_node.raise "Expected scalar as key for mapping"
end
key = key_node.value
{% if properties.size > 0 %}
case key
{% for name, value in properties %}
when {{value[:key]}}
%found{name} = true
begin
%var{name} =
{% if value[:nilable] || value[:has_default] %} YAML::Schema::Core.parse_null_or(value_node) { {% end %}
{% if value[:converter] %}
{{value[:converter]}}.from_yaml(ctx, value_node)
{% elsif value[:type].is_a?(Path) || value[:type].is_a?(Generic) %}
{{value[:type]}}.new(ctx, value_node)
{% else %}
::Union({{value[:type]}}).new(ctx, value_node)
{% end %}
{% if value[:nilable] || value[:has_default] %} } {% end %}
end
{% end %}
else
on_unknown_yaml_attribute(ctx, key, key_node, value_node)
end
{% else %}
on_unknown_yaml_attribute(ctx, key, key_node, value_node)
{% end %}
end
when YAML::Nodes::Scalar
if node.value.empty? && node.style.plain? && !node.tag
# We consider an empty scalar as an empty mapping
else
node.raise "Expected mapping, not #{node.class}"
end
else
node.raise "Expected mapping, not #{node.class}"
end
{% for name, value in properties %}
{% unless value[:nilable] || value[:has_default] %}
if %var{name}.nil? && !%found{name} && !::Union({{value[:type]}}).nilable?
node.raise "Missing YAML attribute: {{value[:key].id}}"
end
{% end %}
{% if value[:nilable] %}
{% if value[:has_default] != nil %}
@{{name}} = %found{name} ? %var{name} : {{value[:default]}}
{% else %}
@{{name}} = %var{name}
{% end %}
{% elsif value[:has_default] %}
@{{name}} = %var{name}.nil? ? {{value[:default]}} : %var{name}
{% else %}
@{{name}} = (%var{name}).as({{value[:type]}})
{% end %}
{% if value[:presence] %}
@{{name}}_present = %found{name}
{% end %}
{% end %}
{% end %}
after_initialize
end
protected def after_initialize
end
protected def on_unknown_yaml_attribute(ctx, key, key_node, value_node)
end
protected def on_to_yaml(yaml : ::YAML::Nodes::Builder)
end
def to_yaml(yaml : ::YAML::Nodes::Builder)
{% begin %}
{% options = @type.annotation(::YAML::Serializable::Options) %}
{% emit_nulls = options && options[:emit_nulls] %}
{% properties = {} of Nil => Nil %}
{% for ivar in @type.instance_vars %}
{% ann = ivar.annotation(::YAML::Field) %}
{% unless ann && ann[:ignore] %}
{%
properties[ivar.id] = {
type: ivar.type,
key: ((ann && ann[:key]) || ivar).id.stringify,
converter: ann && ann[:converter],
emit_null: (ann && (ann[:emit_null] != nil) ? ann[:emit_null] : emit_nulls),
}
%}
{% end %}
{% end %}
yaml.mapping(reference: self) do
{% for name, value in properties %}
_{{name}} = @{{name}}
{% unless value[:emit_null] %}
unless _{{name}}.nil?
{% end %}
{{value[:key]}}.to_yaml(yaml)
{% if value[:converter] %}
if _{{name}}
{{ value[:converter] }}.to_yaml(_{{name}}, yaml)
else
nil.to_yaml(yaml)
end
{% else %}
_{{name}}.to_yaml(yaml)
{% end %}
{% unless value[:emit_null] %}
end
{% end %}
{% end %}
on_to_yaml(yaml)
end
{% end %}
end
module Strict
protected def on_unknown_yaml_attribute(ctx, key, key_node, value_node)
key_node.raise "Unknown yaml attribute: #{key}"
end
end
module Unmapped
@[YAML::Field(ignore: true)]
property yaml_unmapped = Hash(String, YAML::Any).new
protected def on_unknown_yaml_attribute(ctx, key, key_node, value_node)
yaml_unmapped[key] = YAML::Any.new(ctx, value_node)
end
protected def on_to_yaml(yaml)
yaml_unmapped.each do |key, value|
key.to_yaml(yaml)
value.to_yaml(yaml)
end
end
end
end
end