resolves #566 add CLI option to specify a config file containing API options

CHANGELOG.adoc

@@ -35,6 +35,7 @@ Enhancements::
   * Honor `level` and `formatter` keyword arguments passed to Logger constructor (#4250)
   * Set logdev to $stderr if no arguments are passed to Logger constructor (#4250)
   * Add support for skipping TOML front matter (Hugo) when `skip-front-matter` attribute is set (#4300) (*@abhinav*)
+  * Add `-c, --config-file` option to CLI to specify a config file containing API options (#566)
 
 Compliance::
 

lib/asciidoctor/cli/invoker.rb

@@ -46,6 +46,27 @@ def invoke!
         # NOTE in Ruby 2.7, RubyGems sets SOURCE_DATE_EPOCH if it's not set
         ::ENV.delete 'SOURCE_DATE_EPOCH' if (::ENV.key? 'IGNORE_SOURCE_DATE_EPOCH') && (::Gem.respond_to? :source_date_epoch)
 
+        if (config_file = @options[:config_file])
+          require 'yaml'
+          if ::Hash === (config_data = ::YAML.load_file config_file)
+            if ::Hash === (nested_config_data = config_data['asciidoc'] || config_data[:asciidoc])
+              config_data = nested_config_data
+            end
+            config_data.each do |opt_name, opt_val|
+              case (opt_name = opt_name.to_sym)
+              when :attributes
+                if ::Hash === opt_val
+                  opt_val.each_with_object(@options[:attributes] ||= {}) {|(n, v), accum| accum[n] = v }
+                end
+              when :input_file, :output_file, :source_dir, :destination_dir
+                # ignore
+              else
+                @options[opt_name] = opt_val
+              end
+            end
+          end
+        end
+
         @options.map do |key, val|
           case key
           when :input_files

lib/asciidoctor/cli/options.rb

@@ -9,6 +9,7 @@ module Cli
     class Options < ::Hash
       def initialize options = {}
         self[:attributes] = options[:attributes] || {}
+        self[:config_file] = options[:config_file]
         self[:input_files] = options[:input_files]
         self[:output_file] = options[:output_file]
         self[:safe] = options[:safe] || SafeMode::UNSAFE
@@ -99,6 +100,9 @@ def parse! args
             name, _, val = attr.partition '='
             self[:attributes][name] = val
           end
+          opts.on '-c', '--config-file FILE', 'a YAML file that contains API options defined as key-value pairs' do |config_file|
+            self[:config_file] = config_file
+          end
           opts.on '-T', '--template-dir DIR', 'a directory containing custom converter templates that override the built-in converter (requires tilt gem)',
             'may be specified multiple times' do |template_dir|
             if self[:template_dirs].nil?

test/fixtures/config.yml

@@ -0,0 +1,3 @@
+asciidoc:
+  attributes:
+    toc: ''

test/invoker_test.rb

@@ -210,6 +210,20 @@
     assert_equal 'asciidoctor: INFO: possible invalid reference: install', output.chomp
   end
 
+  test 'should allow API options to be passed from config file' do
+    input_path = fixture_path 'sample.adoc'
+    config_path = fixture_path 'config.yml'
+    output = run_command(asciidoctor_cmd, '-c', config_path, '-o', '-', input_path) {|out| out.read }
+    assert_includes output, '<div id="toc" class="toc">'
+  end
+
+  test 'should merge attributes from config file with attributes passed as CLI options' do
+    input_path = fixture_path 'sample.adoc'
+    config_path = fixture_path 'config.yml'
+    output = run_command(asciidoctor_cmd, '-c', config_path, '-a', 'toc-class=interactive-toc', '-o', '-', input_path) {|out| out.read }
+    assert_includes output, '<div id="toc" class="interactive-toc">'
+  end
+
   test 'should not log when --log-level and -q are both specified' do
     input = <<~'EOS'
     skip to <<install>>