Extract WorkspaceStack and loosen Context's coupling to Irb and WorkSpace

The workspace stack lived in Context, but several places changed it
directly, and each had to remember the rules itself, like keeping the
home workspace and loading helper methods. That caused a bug: `pushws
foo` followed by a bare `chws` stayed on `foo` instead of going back to
main.

- Add WorkspaceStack and make it the only place that changes the stack.
- Move the workspace methods from ext/workspaces.rb and ext/change-ws.rb
  into Context, and delete those files.
- Store from_binding on Context, so it no longer asks Irb.
- Stop reading Context's instance variables from outside it.
- Extract WorkSpace.base_binding from WorkSpace#initialize.
- Remove dead code: Context#workspace_home, IrbLoader#old and
  Measure#initialize.

A file loaded with `irb_load file, true` now also gets helper methods
like `conf`.

Author: claude

lib/irb.rb

@@ -98,14 +98,15 @@ class << self
     # The lexer used by this irb session
     attr_accessor :scanner
 
-    attr_reader :from_binding
+    # Whether this session was started by Binding#irb
+    def from_binding
+      @context.from_binding?
+    end
 
     # Creates a new irb session
     def initialize(workspace = nil, input_method = nil, from_binding: false)
-      @from_binding = from_binding
       @prompt_part_cache = nil
-      @context = Context.new(self, workspace, input_method)
-      @context.workspace.load_helper_methods_to_main
+      @context = Context.new(self, workspace, input_method, from_binding: from_binding)
       @signal_status = :IN_IRB
       @scanner = RubyLex.new
       @line_no = 1
@@ -124,9 +125,7 @@ def debug_break
     end
 
     def debug_readline(binding)
-      workspace = IRB::WorkSpace.new(binding)
-      context.replace_workspace(workspace)
-      context.workspace.load_helper_methods_to_main
+      context.replace_workspace(IRB::WorkSpace.new(binding))
       @line_no += 1
 
       # When users run:
@@ -489,12 +488,8 @@ def suspend_name(path = nil, name = nil)
     # Context#workspace.
     #
     # Used by the irb command `irb_load`, see IRB@IRB+Sessions for more information.
-    def suspend_workspace(workspace)
-      current_workspace = @context.workspace
-      @context.replace_workspace(workspace)
-      yield
-    ensure
-      @context.replace_workspace current_workspace
+    def suspend_workspace(workspace, &block)
+      @context.workspaces.with(workspace, &block)
     end
 
     # Evaluates the given block using the given `input_method` as the Context#io.
@@ -503,11 +498,11 @@ def suspend_workspace(workspace)
     # more information.
     def suspend_input_method(input_method)
       back_io = @context.io
-      @context.instance_eval{@io = input_method}
+      @context.io = input_method
       begin
         yield back_io
       ensure
-        @context.instance_eval{@io = back_io}
+        @context.io = back_io
       end
     end
 

lib/irb/command/chws.rb

@@ -3,7 +3,6 @@
 #   change-ws.rb -
 #   	by Keiju ISHITSUKA(keiju@ruby-lang.org)
 #
-require_relative "../ext/change-ws"
 
 module IRB
   # :stopdoc:

lib/irb/command/measure.rb

@@ -8,10 +8,6 @@ class Measure < Base
       category "Misc"
       description "`measure` enables the mode to measure processing time. `measure :off` disables it."
 
-      def initialize(*args)
-        super(*args)
-      end
-
       def execute(arg)
         if arg&.match?(/^do$|^do[^\w]|^\{/)
           warn 'Configure IRB.conf[:MEASURE_PROC] to add custom measure methods.'

lib/irb/command/pushws.rb

@@ -4,8 +4,6 @@
 #   	by Keiju ISHITSUKA(keiju@ruby-lang.org)
 #
 
-require_relative "../ext/workspaces"
-
 module IRB
   # :stopdoc:
 
@@ -15,7 +13,7 @@ class Workspaces < Base
       description "Show workspaces."
 
       def execute(_arg)
-        inspection_results = irb_context.instance_variable_get(:@workspace_stack).map do |ws|
+        inspection_results = irb_context.workspaces.map do |ws|
           truncated_inspect(ws.main)
         end
 

lib/irb/context.rb

@@ -5,6 +5,7 @@
 #
 
 require_relative "workspace"
+require_relative "workspace_stack"
 require_relative "inspector"
 require_relative "input-method"
 require_relative "output-method"
@@ -24,14 +25,10 @@ class Context
     # +nil+::     uses stdin or Reline or Readline
     # +String+::  uses a File
     # +other+::   uses this as InputMethod
-    def initialize(irb, workspace = nil, input_method = nil)
+    def initialize(irb, workspace = nil, input_method = nil, from_binding: false)
       @irb = irb
-      @workspace_stack = []
-      if workspace
-        @workspace_stack << workspace
-      else
-        @workspace_stack << WorkSpace.new
-      end
+      @from_binding = from_binding
+      @workspaces = WorkspaceStack.new(workspace || WorkSpace.new)
       @thread = Thread.current
 
       # copy of default configuration
@@ -190,24 +187,61 @@ def history_file=(hist)
       IRB.conf[:HISTORY_FILE] = hist
     end
 
+    # The stack of workspaces in this context, see WorkspaceStack.
+    attr_reader :workspaces
+
     # Workspace in the current context.
     def workspace
-      @workspace_stack.last
+      @workspaces.current
+    end
+
+    # The workspace this context started with.
+    def home_workspace
+      @workspaces.home
     end
 
     # Replace the current workspace with the given +workspace+.
     def replace_workspace(workspace)
-      @workspace_stack.pop
-      @workspace_stack.push(workspace)
+      @workspaces.replace(workspace)
+    end
+
+    # Changes the current workspace to given object or binding.
+    #
+    # If the optional argument is omitted, the workspace will be
+    # #home_workspace.
+    #
+    # See IRB::WorkSpace.new for more information.
+    def change_workspace(*_main)
+      if _main.empty?
+        replace_workspace(home_workspace)
+        return main
+      end
+
+      replace_workspace(WorkSpace.new(_main[0]))
+    end
+
+    # Creates a new workspace with the given object, and pushes it onto the
+    # workspace stack. Without an argument, swaps the two topmost workspaces.
+    #
+    # See IRB::WorkSpace.new for more information.
+    def push_workspace(*_main)
+      if _main.empty?
+        @workspaces.swap
+      else
+        @workspaces.push(WorkSpace.new(workspace.binding, _main[0]))
+      end
+    end
+
+    # Removes the current workspace from the stack and returns it, or +nil+ if
+    # only the home workspace is left.
+    def pop_workspace
+      @workspaces.pop
     end
 
     # The top-level workspace, see WorkSpace#main
     def main
       workspace.main
     end
-
-    # The toplevel workspace, see #home_workspace
-    attr_reader :workspace_home
     # The current thread in this context.
     attr_reader :thread
     # The current input method.
@@ -565,8 +599,9 @@ def evaluate(statement, line_no) # :nodoc:
       nil
     end
 
+    # Whether this context was started by Binding#irb.
     def from_binding?
-      @irb.from_binding
+      @from_binding
     end
 
     def evaluate_expression(code, line_no) # :nodoc:

lib/irb/ext/change-ws.rb

@@ -92,33 +92,5 @@ def load_file(path, priv = nil)
         end
       end
     end
-
-    def old # :nodoc:
-      back_io = @io
-      back_path = irb_path
-      back_name = @irb_name
-      back_scanner = @irb.scanner
-      begin
-        @io = FileInputMethod.new(path)
-        @irb_name = File.basename(path)
-        self.irb_path = path
-        @irb.signal_status(:IN_LOAD) do
-          if back_io.kind_of?(FileInputMethod)
-            @irb.eval_input
-          else
-            begin
-              @irb.eval_input
-            rescue LoadAbort
-              print "load abort!!\n"
-            end
-          end
-        end
-      ensure
-        @io = back_io
-        @irb_name = back_name
-        self.irb_path = back_path
-        @irb.scanner = back_scanner
-      end
-    end
   end
 end

lib/irb/ext/loader.rb

@@ -9,22 +9,18 @@
 IRB::TOPLEVEL_BINDING = binding
 module IRB # :nodoc:
   class WorkSpace
-    # Creates a new workspace.
-    #
-    # set self to main if specified, otherwise
-    # inherit main from TOPLEVEL_BINDING.
-    def initialize(*main)
-      if Binding === main[0]
-        @binding = main.shift
-      elsif IRB.conf[:SINGLE_IRB]
-        @binding = TOPLEVEL_BINDING
-      else
+    class << self
+      # The binding new workspaces are created from when none is given, as
+      # configured by <code>IRB.conf[:CONTEXT_MODE]</code>.
+      def base_binding
+        return TOPLEVEL_BINDING if IRB.conf[:SINGLE_IRB]
+
         case IRB.conf[:CONTEXT_MODE]
         when 0	# binding in proc on TOPLEVEL_BINDING
-          @binding = eval("proc{binding}.call",
-                          TOPLEVEL_BINDING,
-                          __FILE__,
-                          __LINE__)
+          eval("proc{binding}.call",
+               TOPLEVEL_BINDING,
+               __FILE__,
+               __LINE__)
         when 1	# binding in loaded file
           require "tempfile"
           f = Tempfile.open("irb-binding")
@@ -33,7 +29,7 @@ def initialize(*main)
 EOF
           f.close
           load f.path
-          @binding = $binding
+          $binding
 
         when 2	# binding in loaded file(thread use)
           unless defined? BINDING_QUEUE
@@ -44,17 +40,17 @@ def initialize(*main)
             end
             Thread.pass
           end
-          @binding = BINDING_QUEUE.pop
+          BINDING_QUEUE.pop
 
         when 3	# binding in function on TOPLEVEL_BINDING
-          @binding = eval("self.class.remove_method(:irb_binding) if defined?(irb_binding); private; def irb_binding; binding; end; irb_binding",
-                          TOPLEVEL_BINDING,
-                          __FILE__,
-                          __LINE__ - 3)
+          eval("self.class.remove_method(:irb_binding) if defined?(irb_binding); private; def irb_binding; binding; end; irb_binding",
+               TOPLEVEL_BINDING,
+               __FILE__,
+               __LINE__ - 3)
         when 4  # binding is a copy of TOPLEVEL_BINDING (default)
           # Note that this will typically be IRB::TOPLEVEL_BINDING
           # This is to avoid RubyGems' local variables (see issue #17623)
-          @binding = TOPLEVEL_BINDING.dup
+          TOPLEVEL_BINDING.dup
 
         when 5  # binding in Ruby::Box
           unless defined?(Ruby::Box)
@@ -63,9 +59,17 @@ def initialize(*main)
           end
 
           puts 'Context-mode 5 (binding in Ruby::Box) is experimental. It may be removed or changed without notice.'
-          @binding = Ruby::Box.new.eval('Kernel.binding')
+          Ruby::Box.new.eval('Kernel.binding')
         end
       end
+    end
+
+    # Creates a new workspace.
+    #
+    # set self to main if specified, otherwise
+    # inherit main from TOPLEVEL_BINDING.
+    def initialize(*main)
+      @binding = Binding === main[0] ? main.shift : self.class.base_binding
 
       if main.empty?
         @main = eval("self", @binding)