Loading config file with Ruby head

[MSP-Greg]

Using Ruby head, the Psych gem raises errors when loading a config file, in the following code:

yard/lib/yard/config.rb

Lines 233 to 243 in 9865620

	# Loads the YAML configuration file into memory
	# @return [Hash] the contents of the YAML file from disk
	# @see CONFIG_FILE
	def self.read_config_file
	if File.file?(CONFIG_FILE)
	require 'yaml'
	YAML.load_file(CONFIG_FILE)
	else
	{}
	end
	end

Replacing it with the following fixes the issue.

def self.read_config_file
  if File.file?(CONFIG_FILE)
    require 'yaml'
    if YAML.respond_to?(:safe_load_file)
      begin
        YAML.safe_load_file(CONFIG_FILE)
      rescue Psych::DisallowedClass
        YAML.safe_load_file(CONFIG_FILE, permitted_classes: [SymbolHash, Symbol])
      end
    else
      YAML.load_file(CONFIG_FILE)
    end
  else
    {}
  end
end

Steps to reproduce

My config file has the following, used it for a long time, not sure whether causes the error:

--- !ruby/hash-with-ivars:SymbolHash
elements:
  :stuff
ivars:
  :@symbolize_value: false

Environment details:

• OS: Windows 10
• Ruby version (ruby -v): ruby 3.1.0dev (2021-10-12T08:12:01Z master 2143de251d) [x64-mingw32]
• YARD version (yard -v): yard 0.9.26

Most of my YARD code runs under Windows, as I haven't converted it to Ubuntu. I do not think this issue is platform specific...

I have read the Contributing Guide.