Add core.literal lens.

CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.5.3
+
+* Add core.literal lens.
+
 ## 0.5.2 - 2022-05-20
 
 * Add check.notEmpty lens that throw an error if the input is

README.md

@@ -79,6 +79,7 @@ result = lens.call(input)
 core.dig          - Extract from the input value (object or array) using a path.
 core.chain        - Applies a chain of lenses to an input value
 core.mapping      - Converts the input value via a key:value mapping
+core.literal      - Returns a constant value takens as lens definition
 
 str.strip         - Remove leading and trailing spaces of an input string
 str.split         - Splits the input string as an array

lib/monolens/core.rb

@@ -10,6 +10,11 @@ def dig(options)
     end
     module_function :dig
 
+    def literal(options)
+      Literal.new(options)
+    end
+    module_function :literal
+
     def mapping(options)
       Mapping.new(options)
     end
@@ -21,3 +26,4 @@ def mapping(options)
 require_relative 'core/chain'
 require_relative 'core/dig'
 require_relative 'core/mapping'
+require_relative 'core/literal'

lib/monolens/core/literal.rb

@@ -0,0 +1,11 @@
+module Monolens
+  module Core
+    class Literal
+      include Lens
+
+      def call(arg, world = {})
+        option(:defn)
+      end
+    end
+  end
+end

spec/monolens/core/test_literal.rb

@@ -0,0 +1,13 @@
+require 'spec_helper'
+
+describe Monolens, "core.literal" do
+  let(:lens) do
+    Monolens.lens('core.literal' => { defn: 'hello' })
+  end
+
+  it 'works' do
+    input = {}
+    expected = 'hello'
+    expect(lens.call(input)).to eql(expected)
+  end
+end