[ruby/irb] Encapsulate input details in Statement objects

(https://github.com/ruby/irb/pull/682)

* Introduce Statement class

* Split Statement class for better clarity

https://github.com/ruby/irb/commit/65e8e68690

lib/irb.rb

@@ -570,26 +570,19 @@ module IRB
 
       configure_io
 
-      @scanner.each_top_level_statement do |line, line_no, is_assignment|
+      @scanner.each_top_level_statement do |statement, line_no|
         signal_status(:IN_EVAL) do
           begin
             # If the integration with debugger is activated, we need to handle certain input differently
-            if @context.with_debugger
-              command_class = load_command_class(line)
-              # First, let's pass debugging command's input to debugger
-              # Secondly, we need to let debugger evaluate non-command input
-              # Otherwise, the expression will be evaluated in the debugger's main session thread
-              # This is the only way to run the user's program in the expected thread
-              if !command_class || ExtendCommand::DebugCommand > command_class
-                return line
-              end
+            if @context.with_debugger && statement.should_be_handled_by_debugger?
+              return statement.code
             end
 
-            evaluate_line(line, line_no)
+            @context.evaluate(statement.evaluable_code, line_no)
 
             # Don't echo if the line ends with a semicolon
-            if @context.echo? && !line.match?(/;\s*\z/)
-              if is_assignment
+            if @context.echo? && !statement.suppresses_echo?
+              if statement.is_assignment?
                 if @context.echo_on_assignment?
                   output_value(@context.echo_on_assignment? == :truncate)
                 end
@@ -659,29 +652,6 @@ module IRB
       end
     end
 
-    def evaluate_line(line, line_no)
-      # Transform a non-identifier alias (@, $) or keywords (next, break)
-      command, args = line.split(/\s/, 2)
-      if original = @context.command_aliases[command.to_sym]
-        line = line.gsub(/\A#{Regexp.escape(command)}/, original.to_s)
-        command = original
-      end
-
-      # Hook command-specific transformation
-      command_class = ExtendCommandBundle.load_command(command)
-      if command_class&.respond_to?(:transform_args)
-        line = "#{command} #{command_class.transform_args(args)}"
-      end
-
-      @context.evaluate(line, line_no)
-    end
-
-    def load_command_class(line)
-      command, _ = line.split(/\s/, 2)
-      command_name = @context.command_aliases[command.to_sym]
-      ExtendCommandBundle.load_command(command_name || command)
-    end
-
     def convert_invalid_byte_sequence(str, enc)
       str.force_encoding(enc)
       str.scrub { |c|

lib/irb/ruby-lex.rb

@@ -7,6 +7,7 @@
 require "ripper"
 require "jruby" if RUBY_ENGINE == "jruby"
 require_relative "nesting_parser"
+require_relative "statement"
 
 # :stopdoc:
 class RubyLex
@@ -221,16 +222,30 @@ class RubyLex
       break unless code
 
       if code != "\n"
-        code.force_encoding(@context.io.encoding)
-        yield code, @line_no, assignment_expression?(code)
+        yield build_statement(code), @line_no
       end
       increase_line_no(code.count("\n"))
     rescue TerminateLineInput
     end
   end
 
-  def assignment_expression?(line)
-    # Try to parse the line and check if the last of possibly multiple
+  def build_statement(code)
+    code.force_encoding(@context.io.encoding)
+    command_or_alias, arg = code.split(/\s/, 2)
+    # Transform a non-identifier alias (@, $) or keywords (next, break)
+    command_name = @context.command_aliases[command_or_alias.to_sym]
+    command = command_name || command_or_alias
+    command_class = IRB::ExtendCommandBundle.load_command(command)
+
+    if command_class
+      IRB::Statement::Command.new(code, command, arg, command_class)
+    else
+      IRB::Statement::Expression.new(code, assignment_expression?(code))
+    end
+  end
+
+  def assignment_expression?(code)
+    # Try to parse the code and check if the last of possibly multiple
     # expressions is an assignment type.
 
     # If the expression is invalid, Ripper.sexp should return nil which will
@@ -239,7 +254,7 @@ class RubyLex
     # array of parsed expressions. The first element of each expression is the
     # expression's type.
     verbose, $VERBOSE = $VERBOSE, nil
-    code = "#{RubyLex.generate_local_variables_assign_code(@context.local_variables) || 'nil;'}\n#{line}"
+    code = "#{RubyLex.generate_local_variables_assign_code(@context.local_variables) || 'nil;'}\n#{code}"
     # Get the last node_type of the line. drop(1) is to ignore the local_variables_assign_code part.
     node_type = Ripper.sexp(code)&.dig(1)&.drop(1)&.dig(-1, 0)
     ASSIGNMENT_NODE_TYPES.include?(node_type)

lib/irb/statement.rb

@@ -0,0 +1,78 @@
+# frozen_string_literal: true
+
+module IRB
+  class Statement
+    attr_reader :code
+
+    def is_assignment?
+      raise NotImplementedError
+    end
+
+    def suppresses_echo?
+      raise NotImplementedError
+    end
+
+    def should_be_handled_by_debugger?
+      raise NotImplementedError
+    end
+
+    def evaluable_code
+      raise NotImplementedError
+    end
+
+    class Expression < Statement
+      def initialize(code, is_assignment)
+        @code = code
+        @is_assignment = is_assignment
+      end
+
+      def suppresses_echo?
+        @code.match?(/;\s*\z/)
+      end
+
+      def should_be_handled_by_debugger?
+        true
+      end
+
+      def is_assignment?
+        @is_assignment
+      end
+
+      def evaluable_code
+        @code
+      end
+    end
+
+    class Command < Statement
+      def initialize(code, command, arg, command_class)
+        @code = code
+        @command = command
+        @arg = arg
+        @command_class = command_class
+      end
+
+      def is_assignment?
+        false
+      end
+
+      def suppresses_echo?
+        false
+      end
+
+      def should_be_handled_by_debugger?
+        IRB::ExtendCommand::DebugCommand > @command_class
+      end
+
+      def evaluable_code
+        # Hook command-specific transformation to return valid Ruby code
+        if @command_class.respond_to?(:transform_args)
+          arg = @command_class.transform_args(@arg)
+        else
+          arg = @arg
+        end
+
+        [@command, arg].compact.join(' ')
+      end
+    end
+  end
+end