feat(env): Allow disabling Typelizer with Rails development

We faced an issue which is resolved by disabling Typelizer.
Disabling was hard when Rails env is development, so this commit
changed env name from `TYPELIZER` to `DISABLE_TYPELIZER` and
the logic for disabling.
This commit also adds a description of this environment variable
to README.

README.md

@@ -184,6 +184,10 @@ When [Listen](https://github.com/guard/listen) is installed, Typelizer automatic
 Typelizer.listen = false
 ```
 
+### Disabling Typelizer
+
+Sometimes we want to use Typelizer only with manual generation. To disable Typelizer during development, we can set `DISABLE_TYPELIZER` environment variable to true. This doesn't affect manual generation.
+
 ## Configuration
 
 ### Global Configuration

lib/tasks/generate.rake

@@ -3,7 +3,7 @@ namespace :typelizer do
   task generate: :environment do
     require "benchmark"
 
-    ENV["TYPELIZER"] = "true"
+    ENV["DISABLE_TYPELIZER"] = "false"
 
     puts "Generating TypeScript interfaces..."
     serializers = []

lib/typelizer.rb

@@ -26,7 +26,9 @@
 module Typelizer
   class << self
     def enabled?
-      ENV["RAILS_ENV"] == "development" || ENV["RACK_ENV"] == "development" || ENV["TYPELIZER"] == "true"
+      return false if ENV["DISABLE_TYPELIZER"] == "true" || ENV["DISABLE_TYPELIZER"] == "1"
+
+      ENV["RAILS_ENV"] == "development" || ENV["RACK_ENV"] == "development" || ENV["DISABLE_TYPELIZER"] == "false"
     end
 
     attr_accessor :dirs

spec/spec_helper.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-ENV["TYPELIZER"] = "true"
+ENV["DISABLE_TYPELIZER"] = "false"
 ENV["RAILS_ENV"] = "test"
 require File.expand_path("app/config/environment", __dir__)