Warn on EOL Ruby Versions (#159)

CHANGELOG.md

@@ -1,6 +1,7 @@
 ## 0.6.5 (2018/08/16)
 
 * Fix incorrect http verb when revoking credentials.
+* Warn on EOL ruby versions.
 
 ## 0.6.4 (2018/08/03)
 

README.md

@@ -162,6 +162,17 @@ access and refresh tokens. Two storage implementations are included:
 Custom storage implementations can also be used. See
 [token_store.rb](lib/googleauth/token_store.rb) for additional details.
 
+## Supported Ruby Versions
+
+This library is currently supported on Ruby 1.9+.
+
+However, Ruby 2.4 or later is strongly recommended, as earlier releases have
+reached or are nearing end-of-life. After March 31, 2019, Google will provide
+official support only for Ruby versions that are considered current and
+supported by Ruby Core (that is, Ruby versions that are either in normal
+maintenance or in security maintenance).
+See https://www.ruby-lang.org/en/downloads/branches/ for further details.
+
 ## License
 
 This library is licensed under Apache 2.0. Full license text is

lib/googleauth.rb

@@ -33,3 +33,75 @@ require 'googleauth/credentials'
 require 'googleauth/default_credentials'
 require 'googleauth/user_authorizer'
 require 'googleauth/web_user_authorizer'
+
+module Google
+  # Module Auth provides classes that provide Google-specific authorization
+  # used to access Google APIs.
+  module Auth
+    # rubocop:disable MethodDefParentheses
+
+    # On March 31, 2019, set supported version to 2.4 and recommended to 2.6.
+    # Thereafter, follow the MRI support schedule: supported means non-EOL,
+    # and recommended means in normal (rather than security) maintenance.
+    # See https://www.ruby-lang.org/en/downloads/branches/
+    ##
+    # Minimum "supported" Ruby version (non-EOL)
+    # @private
+    #
+    SUPPORTED_VERSION_THRESHOLD = '1.9'.freeze
+    ##
+    # Minimum "recommended" Ruby version (normal maintenance)
+    # @private
+    #
+    RECOMMENDED_VERSION_THRESHOLD = '2.4'.freeze
+    ##
+    # Check Ruby version and emit a warning if it is old
+    # @private
+    #
+    def self.warn_on_old_ruby_version
+      return if ENV['GOOGLE_CLOUD_SUPPRESS_RUBY_WARNINGS']
+      cur_version = Gem::Version.new RUBY_VERSION
+      if cur_version < Gem::Version.new(SUPPORTED_VERSION_THRESHOLD)
+        warn_unsupported_ruby cur_version, RECOMMENDED_VERSION_THRESHOLD
+      elsif cur_version < Gem::Version.new(RECOMMENDED_VERSION_THRESHOLD)
+        warn_nonrecommended_ruby cur_version, RECOMMENDED_VERSION_THRESHOLD
+      end
+    rescue ArgumentError
+      warn 'Unable to determine current Ruby version.'
+    end
+
+    ##
+    # Print a warning for an EOL version of Ruby
+    # @private
+    #
+    def self.warn_unsupported_ruby cur_version, recommended_version
+      warn "WARNING: You are running Ruby #{cur_version}, which has reached" \
+        ' end-of-life and is no longer supported by Ruby Core.'
+      warn 'The Google Cloud API clients work best on supported versions of' \
+        ' Ruby. It is strongly recommended that you upgrade to Ruby' \
+        " #{recommended_version} or later."
+      warn 'See https://www.ruby-lang.org/en/downloads/branches/ for more' \
+        ' info on the Ruby maintenance schedule.'
+      warn 'To suppress this message, set the' \
+        ' GOOGLE_CLOUD_SUPPRESS_RUBY_WARNINGS environment variable.'
+    end
+
+    ##
+    # Print a warning for a supported but nearing EOL version of Ruby
+    # @private
+    #
+    def self.warn_nonrecommended_ruby cur_version, recommended_version
+      warn "WARNING: You are running Ruby #{cur_version}, which is nearing" \
+        ' end-of-life.'
+      warn 'The Google Cloud API clients work best on supported versions of' \
+        " Ruby. Consider upgrading to Ruby #{recommended_version} or later."
+      warn 'See https://www.ruby-lang.org/en/downloads/branches/ for more' \
+        ' info on the Ruby maintenance schedule.'
+      warn 'To suppress this message, set the' \
+        ' GOOGLE_CLOUD_SUPPRESS_RUBY_WARNINGS environment variable.'
+    end
+    # rubocop:enable MethodDefParentheses
+  end
+end
+
+Google::Auth.warn_on_old_ruby_version

lib/googleauth/version.rb

@@ -31,6 +31,6 @@ module Google
   # Module Auth provides classes that provide Google-specific authorization
   # used to access Google APIs.
   module Auth
-    VERSION = '0.6.4'.freeze
+    VERSION = '0.6.5'.freeze
   end
 end