Add array.coerce.

CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.6.3
+
+* Add `coerce.array`
+
 ## 0.6.2 - 2022-09-29
 
 * Add `key_hash` option to `core.mapping`.

documentation/stdlib/coerce/array.md

@@ -0,0 +1,43 @@
+# coerce.array
+
+Coerces the input value to an array
+
+```
+coerce.array: Any -> Array
+```
+
+This lens convert its input to an Array.
+
+Mimicing ruby, null is coerced to an empty array.
+An array is kept unchanged.
+Any other value is converted to a singleton array.
+
+## Example
+
+Applying the following lens:
+
+```yaml
+---
+array.map:
+  on_error: 'null'
+  lenses:
+  - coerce.array
+```
+
+to the following input:
+
+```yaml
+---
+- ~
+- 'foo'
+- ['foo', 'bar']
+```
+
+will return:
+
+```yaml
+---
+- []
+- ['foo']
+- ['foo', 'bar']
+```

lib/monolens/stdlib/coerce.rb

@@ -22,10 +22,16 @@ def string(options, registry)
     end
     module_function :string
 
+    def array(options, registry)
+      Array.new(options, registry)
+    end
+    module_function :array
+
     Monolens.define_namespace 'coerce', self
   end
 end
 require_relative 'coerce/date'
 require_relative 'coerce/date_time'
 require_relative 'coerce/integer'
 require_relative 'coerce/string'
+require_relative 'coerce/array'

lib/monolens/stdlib/coerce/array.rb

@@ -0,0 +1,13 @@
+module Monolens
+  module Coerce
+    class Array
+      include Lens
+
+      signature(Type::Any, Type::Array)
+
+      def call(arg, world = {})
+        Array(arg)
+      end
+    end
+  end
+end

spec/monolens/stdlib/coerce/test_array.rb

@@ -0,0 +1,13 @@
+require 'spec_helper'
+
+describe Monolens, 'coerce.array' do
+  subject do
+    Monolens.lens('coerce.array')
+  end
+
+  it 'works' do
+    expect(subject.call(12)).to eql([12])
+    expect(subject.call(nil)).to eql([])
+    expect(subject.call([12, 13])).to eql([12, 13])
+  end
+end