Simplify and allow to configure rubocop formatter (#403)

* fix(formatter): avoid temporary files when formatting with RuboCop

By supplying the file content to RubyCop as a in-memory string the same
way as RuboCop's own CLI tool handles STDIN, we completely avoid having
to write any temporary files to disk, and formatting can occur purely
in-memory.

This also has the benefit of Solargraph no longer needing to be
responsible for finding and passing along any config file paths. RuboCop
will correctly find any relevant .rubocop.yml files for the file being
formatted, as RuboCop behaves exactly as if it was running against the
real file in it's original location on disk, except with the content it
is formatting coming from the in-memory string rather than reading it
from the file on disk.

A new blank formatter is also passed to RuboCop, just to make it print
as little as possible to STDOUT, since we don't need and ignore the
STDOUT produced.

* feat(formatter): add "formatter" option to .solargraph.yml

Allows customizing if format command should run safe, or all cops when
formatting files.

Also includes a `extra_args` option to pass custom CLI arguments to
RuboCop. If you primarily only format via solargraph interactively from
an editor, it might be useful to disable certain cops that causes
annoyances in interactive use. For example:

    formatter:
      cops: safe # use "all" to include unsafe cops
      extra_args:
        - --except
        - Lint/Debugger,Lint/UnusedBlockArgument,Lint/UnusedMethodArgument,Style/EmptyMethod

* chore(diagnostics): don't pass .rubocop.yml file path to RuboCop

RuboCop will itself find and use any relevant configuration files based
on the file path of the file it is analyzing. Hence there is no need for
Solargraph to have it's own implementation of this logic.

* chore(formatter): future proof rubocop formatter configuration structure

Solargraph will gain support for multiple formatters soon, so let's
ensure configuration for the rubocop formatter is future proof.

New nested configuration:

    formatter:
      rubocop:
        cops: all
        extra_args: []

Previously:

    formatter:
      cops: all
      extra_args: []

* feat(formatter): add "except" and "only" rubocop formatter options

They take a list or comma separated string of cops, which will be passed
to rubocop as --except and/or --only.

The "except" option is useful to disable cops which can cause annoyance
when using solargraph's formatter as a before save hook in text
editors.

I'm less aware of what the "only" option might be useful for, but might
as well add it so both are covered.

lib/solargraph/diagnostics/rubocop_helpers.rb

@@ -13,32 +13,13 @@ module RubocopHelpers
       # @param code [String]
       # @return [Array(Array<String>, Array<String>)]
       def generate_options filename, code
-        args = ['-f', 'j']
-        rubocop_file = find_rubocop_file(filename)
-        args.push('-c', fix_drive_letter(rubocop_file)) unless rubocop_file.nil?
-        args.push filename
+        args = ['-f', 'j', filename]
         base_options = RuboCop::Options.new
         options, paths = base_options.parse(args)
         options[:stdin] = code
         [options, paths]
       end
 
-      # Find a RuboCop configuration file in a file's directory tree.
-      #
-      # @param filename [String]
-      # @return [String, nil]
-      def find_rubocop_file filename
-        return nil unless File.exist?(filename)
-        filename = File.realpath(filename)
-        dir = File.dirname(filename)
-        until File.dirname(dir) == dir
-          here = File.join(dir, '.rubocop.yml')
-          return here if File.exist?(here)
-          dir = File.dirname(dir)
-        end
-        nil
-      end
-
       # RuboCop internally uses capitalized drive letters for Windows paths,
       # so we need to convert the paths provided to the command.
       #

lib/solargraph/language_server/host.rb

@@ -494,6 +494,11 @@ def read_text uri
         library.read_text(filename)
       end
 
+      def formatter_config uri
+        library = library_for(uri)
+        library.workspace.config.formatter
+      end
+
       # @param uri [String]
       # @param line [Integer]
       # @param column [Integer]

lib/solargraph/language_server/message/text_document/formatting.rb

@@ -11,29 +11,58 @@ module TextDocument
         class Formatting < Base
           include Solargraph::Diagnostics::RubocopHelpers
 
+          class BlankRubocopFormatter < ::RuboCop::Formatter::BaseFormatter; end
+
           def process
-            filename = uri_to_file(params['textDocument']['uri'])
-            Dir.mktmpdir do |tempdir|
-              tempfile = File.join(tempdir, File.basename(filename))
-              rubocop_file = Diagnostics::RubocopHelpers.find_rubocop_file(filename)
-              original = host.read_text(params['textDocument']['uri'])
-              File.write tempfile, original
-              begin
-                args = ['-a', '-f', 'fi', tempfile]
-                args.unshift('-c', fix_drive_letter(rubocop_file)) unless rubocop_file.nil?
-                options, paths = RuboCop::Options.new.parse(args)
-                store = RuboCop::ConfigStore.new
-                redirect_stdout { RuboCop::Runner.new(options, store).run(paths) }
-                result = File.read(tempfile)
-                format original, result
-              rescue RuboCop::ValidationError, RuboCop::ConfigNotFoundError => e
-                set_error(Solargraph::LanguageServer::ErrorCodes::INTERNAL_ERROR, "[#{e.class}] #{e.message}")
-              end
+            file_uri = params['textDocument']['uri']
+            config = config_for(file_uri)
+            original = host.read_text(file_uri)
+            args = cli_args(file_uri, config)
+
+            options, paths = RuboCop::Options.new.parse(args)
+            options[:stdin] = original
+            redirect_stdout do
+              RuboCop::Runner.new(options, RuboCop::ConfigStore.new).run(paths)
             end
+            result = options[:stdin]
+
+            format original, result
+          rescue RuboCop::ValidationError, RuboCop::ConfigNotFoundError => e
+            set_error(Solargraph::LanguageServer::ErrorCodes::INTERNAL_ERROR, "[#{e.class}] #{e.message}")
           end
 
           private
 
+          def config_for(file_uri)
+            conf = host.formatter_config(file_uri)
+            return {} unless conf.is_a?(Hash)
+
+            conf['rubocop'] || {}
+          end
+
+          def cli_args file, config
+            args = [
+              config['cops'] == 'all' ? '--auto-correct-all' : '--auto-correct',
+              '--cache', 'false',
+              '--format', 'Solargraph::LanguageServer::Message::' \
+                          'TextDocument::Formatting::BlankRubocopFormatter',
+            ]
+
+            ['except', 'only'].each do |arg|
+              cops = cop_list(config[arg])
+              args += ["--#{arg}", cops] if cops
+            end
+
+            args += config['extra_args'] if config['extra_args']
+            args + [file]
+          end
+
+          def cop_list(value)
+            value = value.join(',') if value.respond_to?(:join)
+            return nil if value == '' || !value.is_a?(String)
+            value
+          end
+
           # @param original [String]
           # @param result [String]
           # @return [void]

lib/solargraph/workspace/config.rb

@@ -85,6 +85,13 @@ def reporters
         raw_data['reporters']
       end
 
+      # A hash of options supported by the formatter
+      #
+      # @return [Hash]
+      def formatter
+        raw_data['formatter']
+      end
+
       # An array of plugins to require.
       #
       # @return [Array<String>]
@@ -144,6 +151,14 @@ def default_config
           'require' => [],
           'domains' => [],
           'reporters' => %w[rubocop require_not_found],
+          'formatter' => {
+            'rubocop' => {
+              'cops' => 'safe',
+              'except' => [],
+              'only' => [],
+              'extra_args' =>[]
+            }
+          },
           'require_paths' => [],
           'plugins' => [],
           'max_files' => MAX_FILES

spec/diagnostics/rubocop_helpers_spec.rb

@@ -1,11 +1,4 @@
 describe Solargraph::Diagnostics::RubocopHelpers do
-  it "finds a .rubocop.yml file in a parent directory" do
-    file = File.realpath(File.join 'spec', 'fixtures', 'rubocop-subfolder-configuration', 'folder1', 'folder2', 'test.rb')
-    conf = File.realpath(File.join 'spec', 'fixtures', 'rubocop-subfolder-configuration', '.rubocop.yml')
-    found = Solargraph::Diagnostics::RubocopHelpers.find_rubocop_file(file)
-    expect(found).to eq(conf)
-  end
-
   it "converts lower-case drive letters to upper-case" do
     input = 'c:/one/two'
     output = Solargraph::Diagnostics::RubocopHelpers.fix_drive_letter(input)

spec/language_server/message/text_document/formatting_spec.rb

@@ -1,6 +1,6 @@
 describe Solargraph::LanguageServer::Message::TextDocument::Formatting do
   it 'gracefully handles empty files' do
-    host = double(:Host, read_text: '')
+    host = double(:Host, read_text: '', formatter_config: {})
     request = {
       'params' => {
           'textDocument' => {