Add an interactive console for users as well (#21803)

* Add an interactive console for users as well

* Proposed documentation

* Apply copy suggestions.

* Format copy.

---------

Co-authored-by: Roger Oba <rogerluan.oba@gmail.com>

ToolsAndDebugging.md

@@ -2,6 +2,12 @@
 
 For detailed instructions on how to get started with contributing to _fastlane_, first check out [YourFirstPR.md][first-pr] and [Testing.md](Testing.md). This guide will focus on more advanced instructions on how to debug _fastlane_ and _spaceship_ issues and work on patches.
 
+## Experiment with the _fastlane_ internals
+
+Open a _fastlane_ console by running `fastlane console` inside or outside your project.
+
+This will allow you to invoke any of the _fastlane_ modules and classes and test their behavior.
+
 ## Debug using [pry](https://pry.github.io/)
 
 Before you’re able to use [pry](https://pry.github.io/), make sure to have completed the [YourFirstPR.md][first-pr] setup part, as this will install all required development dependencies.

fastlane/lib/fastlane/commands_generator.rb

@@ -249,6 +249,15 @@ def run
         end
       end
 
+      command :console do |c|
+        c.syntax = 'fastlane console'
+        c.description = 'Opens an interactive developer console'
+        c.action do |args, options|
+          require 'fastlane/console'
+          Fastlane::Console.execute(args, options)
+        end
+      end
+
       command :enable_auto_complete do |c|
         c.syntax = 'fastlane enable_auto_complete'
         c.description = 'Enable tab auto completion'

fastlane/lib/fastlane/console.rb

@@ -0,0 +1,24 @@
+require 'irb'
+
+module Fastlane
+  # Opens an interactive developer console
+  class Console
+    def self.execute(args, options)
+      ARGV.clear
+      IRB.setup(nil)
+      @irb = IRB::Irb.new(nil)
+      IRB.conf[:MAIN_CONTEXT] = @irb.context
+      IRB.conf[:PROMPT][:FASTLANE] = IRB.conf[:PROMPT][:SIMPLE].dup
+      IRB.conf[:PROMPT][:FASTLANE][:RETURN] = "%s\n"
+      @irb.context.prompt_mode = :FASTLANE
+      @irb.context.workspace = IRB::WorkSpace.new(binding)
+      trap('INT') do
+        @irb.signal_handle
+      end
+
+      UI.message('Welcome to fastlane interactive!')
+
+      catch(:IRB_EXIT) { @irb.eval_input }
+    end
+  end
+end