Don't assume we have Rails.env if we have Rails

As referenced in #1739

Just because the `Rails` constant is defined, it doesn't mean we're
actually in a Rails app. Since there are people who use Paperclip
outside of Rails, and there's no reason we shouldn't be able to run in
those situations. This commit checks for `Rails.env` instead of just
checking for `Rails` and assuming `Rails.env` works.

Gemfile

@@ -2,7 +2,7 @@ source "https://rubygems.org"
 
 gemspec
 
-gem 'sqlite3', '1.3.8', :platforms => :ruby
+gem 'sqlite3', '~>1.3.8', :platforms => :ruby
 
 gem 'jruby-openssl', :platforms => :jruby
 gem 'activerecord-jdbcsqlite3-adapter', :platforms => :jruby

lib/paperclip.rb

@@ -55,6 +55,7 @@
 require 'paperclip/has_attached_file'
 require 'paperclip/attachment_registry'
 require 'paperclip/filename_cleaner'
+require 'paperclip/rails_environment'
 require 'mime/types'
 require 'logger'
 require 'cocaine'

lib/paperclip/rails_environment.rb

@@ -0,0 +1,23 @@
+module Paperclip
+  class RailsEnvironment
+    def self.get
+      new.get
+    end
+
+    def get
+      if rails_exists? && rails_environment_exists?
+        Rails.env
+      else
+        nil
+      end
+    end
+
+    def rails_exists?
+      Object.const_defined?("Rails")
+    end
+
+    def rails_environment_exists?
+      Rails.respond_to?(:env)
+    end
+  end
+end

lib/paperclip/storage/fog.rb

@@ -156,8 +156,7 @@ def expiring_url(time = (Time.now + 3600), style_name = default_style)
 
       def parse_credentials(creds)
         creds = find_credentials(creds).stringify_keys
-        env = Object.const_defined?(:Rails) ? Rails.env : nil
-        (creds[env] || creds).symbolize_keys
+        (creds[RailsEnvironment.get] || creds).symbolize_keys
       end
 
       def copy_to_local_file(style, local_dest_path)

lib/paperclip/storage/s3.rb

@@ -288,8 +288,7 @@ def set_storage_class(storage_class)
       def parse_credentials creds
         creds = creds.respond_to?('call') ? creds.call(self) : creds
         creds = find_credentials(creds).stringify_keys
-        env = Object.const_defined?(:Rails) ? Rails.env : nil
-        (creds[env] || creds).symbolize_keys
+        (creds[RailsEnvironment.get] || creds).symbolize_keys
       end
 
       def exists?(style = default_style)

spec/paperclip/rails_environment_spec.rb

@@ -0,0 +1,33 @@
+require 'spec_helper'
+
+describe Paperclip::RailsEnvironment do
+
+  it "returns nil when Rails isn't defined" do
+    resetting_rails_to(nil) do
+      expect(Paperclip::RailsEnvironment.get).to be_nil
+    end
+  end
+
+  it "returns nil when Rails.env isn't defined" do
+    resetting_rails_to({}) do
+      expect(Paperclip::RailsEnvironment.get).to be_nil
+    end
+  end
+
+  it "returns the value of Rails.env if it is set" do
+    resetting_rails_to(OpenStruct.new(env: "foo")) do
+      expect(Paperclip::RailsEnvironment.get).to eq "foo"
+    end
+  end
+
+  def resetting_rails_to(new_value)
+    begin
+      previous_rails = Object.send(:remove_const, "Rails")
+      Object.const_set("Rails", new_value) unless new_value.nil?
+      yield
+    ensure
+      Object.send(:remove_const, "Rails") if Object.const_defined?("Rails")
+      Object.const_set("Rails", previous_rails)
+    end
+  end
+end