Merge pull request #155 from ok32/validation

Add optional config validation (using dry-validation schema)

README.md

@@ -275,6 +275,29 @@ located at `config/initializers/config.rb`.
 
 Check [Deep Merge](https://github.com/danielsdeleo/deep_merge) for more details.
 
+### Validation
+
+You can optionally define a schema to validate presence (and type) of specific config values:
+
+```ruby
+Config.setup do |config|
+  # ...
+  config.schema do
+    required(:youtube).schema do
+      required(:api_key).filled
+    end
+  end
+end
+```
+
+The above example demonstrates how to ensure that the configuration has the `youtube` structure
+with the `api_key` field filled.
+If you define a schema it will automatically be used to validate your config. If validation fails it will
+raise a `Config::ValidationError` containing a nice message with information about all the mismatches
+between the schema and your config.
+
+Check [dry-validation](https://github.com/dry-rb/dry-validation) for more details.
+
 ### Environment variables
 
 See section below for more details.

config.gemspec

@@ -26,6 +26,7 @@ Gem::Specification.new do |s|
 
   s.add_dependency 'activesupport',           '>= 3.0'
   s.add_dependency 'deep_merge',              '~> 1.1.1'
+  s.add_dependency 'dry-validation',          '~> 0.10.3'
 
   s.add_development_dependency 'bundler',     '~> 1.13',  '>= 1.13.1'
   s.add_development_dependency 'rake',        '~> 11.2',  '>= 11.2.2'

lib/config.rb

@@ -1,14 +1,18 @@
 require 'active_support/core_ext/module/attribute_accessors'
 
 require 'config/compatibility'
+require 'config/validation'
 require 'config/options'
 require 'config/version'
 require 'config/integrations/rails/engine' if defined?(::Rails)
 require 'config/sources/yaml_source'
 require 'config/sources/hash_source'
 require 'deep_merge'
+require 'dry-validation'
 
 module Config
+  class ValidationError < StandardError; end
+
   # Ensures the setup only gets run once
   @@_ran_once = false
 
@@ -25,11 +29,22 @@ module Config
   @@knockout_prefix = nil
   @@overwrite_arrays = true
 
+  mattr_writer :schema
+  @@schema = nil
+
   def self.setup
     yield self if @@_ran_once == false
     @@_ran_once = true
   end
 
+  def self.schema(&block)
+    if block_given?
+      @@schema = Dry::Validation.Schema(&block)
+    else
+      @@schema
+    end
+  end
+
   # Create a populated Options instance from a settings file. If a second file is given, then the sections of that
   # file will overwrite existing sections of the first file.
   def self.load_files(*files)

lib/config/options.rb

@@ -3,6 +3,7 @@
 module Config
   class Options < OpenStruct
     include Enumerable
+    include Validation
 
     def keys
       marshal_dump.keys
@@ -83,6 +84,7 @@ def reload!
       marshal_load(__convert(conf).marshal_dump)
 
       reload_env! if Config.use_env
+      validate! if Config.schema
 
       self
     end

lib/config/validation.rb

@@ -0,0 +1,28 @@
+module Config
+  module Validation
+    def validate!
+      v_res = Config.schema.(self.to_hash)
+
+      unless v_res.success?
+        raise ValidationError.new("Config validation failed:\n\n#{format_errors(v_res)}")
+      end
+    end
+
+    def format_errors(v_res)
+      flatten_hash(v_res.messages).map do |field, msgs|
+        "#{' ' * 2}#{field}: #{msgs.join('; ')}"
+      end.join('\n')
+    end
+
+    def flatten_hash(h, acc={}, pref=[])
+      h.inject(acc) do |a, (k,v)|
+        if v.is_a?(Hash)
+          flatten_hash(v, acc, pref + [k])
+        else
+          acc[(pref + [k]).join('.')] = v
+          acc
+        end
+      end
+    end
+  end
+end

spec/config_spec.rb

@@ -367,4 +367,38 @@
 
     end
   end
+
+  context 'validation' do
+    around(:each) do |example|
+      Config.reset
+      example.run
+      Config.reset
+    end
+
+    it 'should raise if schema is present and validation fails' do
+      Config.setup do |config|
+        config.schema do
+          required(:youtube).schema do
+            required(:nonexist_field).filled
+          end
+        end
+      end
+
+      expect { Config.load_files("#{fixture_path}/validation/config.yml") }.
+        to raise_error(Config::ValidationError, /youtube.nonexist_field: is missing/)
+    end
+
+    it 'should work if validation passes' do
+      Config.setup do |config|
+        config.schema do
+          required(:youtube).schema do
+            required(:api_key).filled
+          end
+        end
+      end
+
+      expect { Config.load_files("#{fixture_path}/validation/config.yml") }.
+        to_not raise_error
+    end
+  end
 end

spec/fixtures/validation/config.yml

@@ -0,0 +1,2 @@
+youtube:
+  api_key: ADSEF453

spec/spec_helper.rb

@@ -47,6 +47,8 @@ def self.reset
         self.use_env          = false
         self.knockout_prefix  = nil
         self.overwrite_arrays = true
+        self.schema           = nil
+        class_variable_set(:@@_ran_once, false)
       end
     end
   end