add json parser

Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    decanter (5.0.0)
+    decanter (5.1.0)
       actionpack (>= 7.1.3.2)
       activesupport
       rails (>= 7.1.3.2)

README.md

@@ -12,21 +12,31 @@ gem 'decanter', '~> 5.0'
 
 ## Contents
 
-- [Basic Usage](#basic-usage)
-  - [Decanters](#decanters)
-  - [Generators](#generators)
-  - [Decanting Collections](#decanting-collections)
-  - [Nested resources](#nested-resources)
-  - [Default parsers](#default-parsers)
-  - [Parser options](#parser-options)
-  - [Exceptions](#exceptions)
-- [Advanced usage](#advanced-usage)
-  - [Custom parsers](#custom-parsers)
-  - [Squashing inputs](#squashing-inputs)
-  - [Chaining parsers](#chaining-parsers)
-  - [Requiring params](#requiring-params)
-  - [Global configuration](#global-configuration)
-- [Contributing](#contributing)
+- [Decanter](#decanter)
+  - [Migration Guides](#migration-guides)
+  - [Contents](#contents)
+  - [Basic Usage](#basic-usage)
+    - [Decanters](#decanters)
+    - [Generators](#generators)
+      - [Decanters](#decanters-1)
+      - [Parsers](#parsers)
+      - [Resources](#resources)
+    - [Decanting Collections](#decanting-collections)
+      - [Control Over Decanting Collections](#control-over-decanting-collections)
+    - [Nested resources](#nested-resources)
+    - [Default parsers](#default-parsers)
+    - [Parser options](#parser-options)
+    - [Exceptions](#exceptions)
+  - [Advanced Usage](#advanced-usage)
+    - [Custom Parsers](#custom-parsers)
+      - [Custom parser methods](#custom-parser-methods)
+      - [Custom parser base classes](#custom-parser-base-classes)
+    - [Squashing inputs](#squashing-inputs)
+    - [Chaining parsers](#chaining-parsers)
+    - [Requiring params](#requiring-params)
+    - [Default values](#default-values)
+    - [Global configuration](#global-configuration)
+  - [Contributing](#contributing)
 
 ## Basic Usage
 
@@ -163,13 +173,19 @@ Decanter comes with the following parsers out of the box:
 - `:phone`
 - `:string`
 - `:array`
+- `:json`
 
 Note: these parsers are designed to operate on a single value, except for `:array`. This parser expects an array, and will use the `parse_each` option to call a given parser on each of its elements:
 
 ```ruby
 input :ids, :array, parse_each: :integer
 ```
 
+The `:json` parser may also accept an array, but the array must be provided as a single JSON-encoded string value:
+```
+'["abc", "def"]'
+```
+
 ### Parser options
 
 Some parsers can receive options that modify their behavior. These options are passed in as named arguments to `input`:

lib/decanter/parser/json_parser.rb

@@ -0,0 +1,20 @@
+module Decanter
+  module Parser
+    class JsonParser < ValueParser
+
+      parser do |val, options|
+        next if val.nil? || val === ''
+        raise Decanter::ParseError.new 'Expects a JSON string' unless val.is_a?(String)
+        parse_json(val)
+      end
+
+      def self.parse_json(val)
+        begin
+          JSON.parse(val)
+        rescue 
+          raise Decanter::ParseError.new 'Invalid JSON string'
+        end
+      end
+    end
+  end
+end

lib/decanter/version.rb

@@ -1,3 +1,3 @@
 module Decanter
-  VERSION = '5.0.0'.freeze
+  VERSION = '5.1.0'.freeze
 end

spec/decanter/parser/json_parser_spec.rb

@@ -0,0 +1,48 @@
+require 'spec_helper'
+
+describe 'JsonParser' do
+
+  let(:name) { :foo }
+
+  let(:parser) { Decanter::Parser::JsonParser }
+
+  describe '#parse' do
+
+  context 'with a valid JSON string' do
+    it 'parses the string value and returns a parsed JSON' do
+      expect(parser.parse(name, '{"key": "value"}')).to match({name => {"key" => "value"}})
+      expect(parser.parse(name, '["hello", "goodbye"]')).to match({name => ["hello", "goodbye"]})
+    end
+  end
+
+    context 'with empty string' do
+      it 'returns nil' do
+        expect(parser.parse(name, '')).to match({name => nil})
+      end
+    end
+
+    context 'with nil' do
+      it 'returns nil' do
+        expect(parser.parse(name, nil)).to match({name => nil})
+      end
+    end
+
+    context 'with a non-string value' do
+      it 'raises a Decanter::ParseError' do
+        expect { parser.parse(name, 1) }.to raise_error(Decanter::ParseError, 'Expects a JSON string')
+        expect { parser.parse(name, true) }.to raise_error(Decanter::ParseError, 'Expects a JSON string')
+        expect { parser.parse(name, {}) }.to raise_error(Decanter::ParseError, 'Expects a JSON string')
+      end
+    end
+
+    context 'with a string that is invalid JSON' do
+      json_parser_error = 'Invalid JSON string'
+      it 'raises a Decanter::ParseError' do
+        expect { parser.parse(name, 'invalid') }.to raise_error(Decanter::ParseError, json_parser_error)
+        expect { parser.parse(name, '{ name: "John Smith", age: 30 }') }.to raise_error(Decanter::ParseError, json_parser_error)
+        expect { parser.parse(name, '{\"bio\": \"Line1 \n Line2\"}') }.to raise_error(Decanter::ParseError, json_parser_error)
+        expect { parser.parse(name, '{ "name": "John Smith", "age": 30, }') }.to raise_error(Decanter::ParseError, json_parser_error)
+      end
+    end
+  end
+end