Read command line options from ./.rubocop file and RUBOCOP_OPTS env v…

…ariable. (rubocop#3003)

This may be useful when running rubocop using another tool, for example [pronto](https://github.com/mmozuras/pronto).

Default command-line options are loaded from `.rubocop` and `RUBOCOP_OPTS` and are combined with command-line options that are explicitly passed to `rubocop`.
Thus, the options have the following order of precedence (from highest to lowest):

1. Explicit command-line options
2. Options from `RUBOCOP_OPTS` environment variable
3. Options from `.rubocop` file.

CHANGELOG.md

@@ -8,6 +8,7 @@
 * [#2928](https://github.com/bbatsov/rubocop/issues/2928): `Style/NestedParenthesizedCalls` cop can auto-correct. ([@drenmi][])
 * `Style/RaiseArgs` cop can auto-correct. ([@drenmi][])
 * [#2993](https://github.com/bbatsov/rubocop/pull/2993): `Style/SpaceAfterColon` now checks optional keyword arguments. ([@owst][])
+* [#3003](https://github.com/bbatsov/rubocop/pull/3003): Read command line options from `.rubocop` file and `RUBOCOP_OPTS` environment variable. ([@bolshakov][])
 
 ### Bug fixes
 
@@ -2104,3 +2105,4 @@
 [@amuino]: https://github.com/amuino
 [@dylanahsmith]: https://github.com/dylanahsmith
 [@gerrywastaken]: https://github.com/gerrywastaken
+[@bolshakov]: https://github.com/bolshakov

README.md

@@ -203,6 +203,13 @@ Command flag              | Description
 `-s/--stdin`              | Pipe source from STDIN. This is useful for editor integration.
 `--[no-]color`            | Force color output on or off.
 
+Default command-line options are loaded from `.rubocop` and `RUBOCOP_OPTS` and are combined with command-line options that are explicitly passed to `rubocop`.
+Thus, the options have the following order of precedence (from highest to lowest):
+
+1. Explicit command-line options
+2. Options from `RUBOCOP_OPTS` environment variable
+3. Options from `.rubocop` file.
+
 ### Cops
 
 In RuboCop lingo the various checks performed on the code are called cops. There are several cop departments.

lib/rubocop/options.rb

@@ -2,6 +2,7 @@
 # frozen_string_literal: true
 
 require 'optparse'
+require 'shellwords'
 
 module RuboCop
   # This class handles command line options.
@@ -14,7 +15,8 @@ def initialize
       @validator = OptionsValidator.new(@options)
     end
 
-    def parse(args)
+    def parse(command_line_args)
+      args = args_from_file.concat(args_from_env).concat(command_line_args)
       define_options(args).parse!(args)
       # The --no-color CLI option sets `color: false` so we don't want the
       # `no_color` key, which is created automatically.
@@ -31,6 +33,18 @@ def parse(args)
 
     private
 
+    def args_from_file
+      if File.exist?('.rubocop')
+        IO.readlines('.rubocop').map(&:strip)
+      else
+        []
+      end
+    end
+
+    def args_from_env
+      Shellwords.split(ENV.fetch('RUBOCOP_OPTS', ''))
+    end
+
     def define_options(args)
       OptionParser.new do |opts|
         opts.banner = 'Usage: rubocop [options] [file1, file2, ...]'

spec/rubocop/options_spec.rb

@@ -262,4 +262,48 @@ def abs(path)
       end
     end
   end
+
+  describe 'options precedence' do
+    def with_env_options(options)
+      ENV['RUBOCOP_OPTS'] = options
+      yield
+    ensure
+      ENV.delete('RUBOCOP_OPTS')
+    end
+    let(:command_line_options) { %w(--no-color) }
+
+    subject { options.parse(command_line_options).first }
+
+    context '.rubocop file' do
+      before do
+        create_file('.rubocop', %w(--color --fail-level C))
+      end
+
+      it 'has lower precedence then command line options' do
+        is_expected.to eq(color: false, fail_level: :convention)
+      end
+
+      it 'has lower precedence then options from RUBOCOP_OPTS env variable' do
+        with_env_options '--fail-level W' do
+          is_expected.to eq(color: false, fail_level: :warning)
+        end
+      end
+    end
+
+    context 'RUBOCOP_OPTS environment variable' do
+      it 'has lower precedence then command line options' do
+        with_env_options '--color' do
+          is_expected.to eq(color: false)
+        end
+      end
+
+      it 'has higher precedence then options from .rubocop file' do
+        create_file('.rubocop', %w(--color --fail-level C))
+
+        with_env_options '--fail-level W' do
+          is_expected.to eq(color: false, fail_level: :warning)
+        end
+      end
+    end
+  end
 end