Refactor workspace management into dedicated WorkspaceStack class

[st0012]

Summary

This PR refactors IRB's workspace management by extracting workspace stack logic into a dedicated WorkspaceStack class. This improves code organization, encapsulation, and makes workspace operations more explicit and testable.

Key Changes

• New WorkspaceStack class (lib/irb/workspace_stack.rb):

  • Manages the stack of workspaces with a fixed home workspace at the bottom
  • Provides methods: push, pop, swap, replace, and with (context manager)
  • Automatically loads helper methods when workspaces become current
  • Includes Enumerable for iteration support

• Refactored Context class:

  • Replaced @workspace_stack array with @workspaces (WorkspaceStack instance)
  • Added from_binding parameter to initialize to track if context was started by Binding#irb
  • Moved from_binding? logic from IRB class to Context
  • Added home_workspace accessor to get the initial workspace
  • Integrated change_workspace and push_workspace methods directly into Context (previously in extension files)
  • Moved evaluate method logic to IRB class as evaluate_statement

• Refactored WorkSpace class:

  • Extracted binding creation logic into class method base_binding
  • Simplified initialize to use the new base_binding method

• Updated IRB class:

  • Moved from_binding to a method that delegates to @context.from_binding?
  • Removed manual helper method loading (now handled by WorkspaceStack)
  • Moved statement evaluation logic to new evaluate_statement method
  • Simplified suspend_workspace to use WorkspaceStack#with
  • Improved suspend_input_method to use direct property assignment instead of instance_eval

• Removed extension files:

  • lib/irb/ext/change-ws.rb - functionality moved to Context
  • lib/irb/ext/workspaces.rb - functionality moved to Context
  • Removed unused old method from lib/irb/ext/loader.rb

• Added comprehensive tests (test/irb/test_workspace_stack.rb):

  • Tests for push/pop operations
  • Tests for swap functionality
  • Tests for replace and with (context manager) operations
  • Tests for helper method loading on workspace changes

• Minor improvements:

  • Removed unnecessary initialize method from Measure command
  • Updated command implementations to use new workspaces accessor

Notable Implementation Details

• The WorkspaceStack ensures the home workspace is never removed from the stack
• Helper methods are loaded into a workspace's main object when it becomes current, centralizing this responsibility
• The with method provides exception-safe temporary workspace switching
• All workspace operations now go through WorkspaceStack, making it the single source of truth for workspace management

https://claude.ai/code/session_0175QjMQGeUPByLSqoL6ye5U