Fix usage of tracer gem and add tests

The new tests are skipped when ruby below 3.1, as it was a default gem on it, and in a version we do not support.

This also move definition of `use_tracer` to module Context instead of monkey patch.

.github/workflows/test.yml

@@ -25,17 +25,19 @@ jobs:
         run: bundle exec rubocop
   irb:
     needs: ruby-versions
-    name: rake test ${{ matrix.ruby }} ${{ matrix.with_latest_reline && '(latest reline)' || '' }}
+    name: rake test ${{ matrix.ruby }} ${{ matrix.with_latest_reline && '(latest reline)' || '' }} ${{ matrix.with_tracer && '(with tracer)' || '' }}
     strategy:
       matrix:
         ruby: ${{ fromJson(needs.ruby-versions.outputs.versions) }}
         with_latest_reline: [true, false]
+        with_tracer: [true, false]
         exclude:
           - ruby: truffleruby
       fail-fast: false
     runs-on: ubuntu-latest
     env:
       WITH_LATEST_RELINE: ${{matrix.with_latest_reline}}
+      WITH_TRACER: ${{matrix.with_tracer}}
     timeout-minutes: 30
     steps:
       - uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11

Gemfile

@@ -19,6 +19,7 @@ gem "test-unit-ruby-core"
 
 gem "rubocop"
 
+gem "tracer" if ENV["WITH_TRACER"] == "true"
 gem "debug", github: "ruby/debug", platforms: [:mri, :mswin]
 
 if RUBY_VERSION >= "3.0.0" && !is_truffleruby

lib/irb/context.rb

@@ -161,6 +161,11 @@ def initialize(irb, workspace = nil, input_method = nil)
 
     private_constant :KEYWORD_ALIASES
 
+    def use_tracer=(val)
+      require_relative "ext/tracer"
+      @use_tracer = val
+    end
+
     private def build_completor
       completor_type = IRB.conf[:COMPLETOR]
       case completor_type

lib/irb/ext/tracer.rb

@@ -3,76 +3,30 @@
 #   irb/lib/tracer.rb -
 #   	by Keiju ISHITSUKA([email protected])
 #
-
+# Loading the gem "tracer" will cause it to extend IRB commands with:
+# https://github.com/ruby/tracer/blob/v0.2.2/lib/tracer/irb.rb
 begin
   require "tracer"
 rescue LoadError
   $stderr.puts "Tracer extension of IRB is enabled but tracer gem wasn't found."
-  module IRB
-    class Context
-      def use_tracer=(opt)
-        # do nothing
-      end
-    end
-  end
   return # This is about to disable loading below
 end
 
 module IRB
-
-  # initialize tracing function
-  def IRB.initialize_tracer
-    Tracer.verbose = false
-    Tracer.add_filter {
-      |event, file, line, id, binding, *rests|
-      /^#{Regexp.quote(@CONF[:IRB_LIB_PATH])}/ !~ file and
-        File::basename(file) != "irb.rb"
-    }
-  end
-
-  class Context
-    # Whether Tracer is used when evaluating statements in this context.
-    #
-    # See +lib/tracer.rb+ for more information.
-    attr_reader :use_tracer
-    alias use_tracer? use_tracer
-
-    # Sets whether or not to use the Tracer library when evaluating statements
-    # in this context.
-    #
-    # See +lib/tracer.rb+ for more information.
-    def use_tracer=(opt)
-      if opt
-        Tracer.set_get_line_procs(@irb_path) {
-          |line_no, *rests|
-          @io.line(line_no)
-        }
-      elsif !opt && @use_tracer
-        Tracer.off
-      end
-      @use_tracer=opt
-    end
-  end
-
   class WorkSpace
     alias __evaluate__ evaluate
     # Evaluate the context of this workspace and use the Tracer library to
     # output the exact lines of code are being executed in chronological order.
     #
-    # See +lib/tracer.rb+ for more information.
-    def evaluate(context, statements, file = nil, line = nil)
-      if context.use_tracer? && file != nil && line != nil
-        Tracer.on
-        begin
+    # See https://github.com/ruby/tracer for more information.
+    def evaluate(statements, file = __FILE__, line = __LINE__)
+      if IRB.conf[:USE_TRACER] == true
+        CallTracer.new(colorize: Color.colorable?).start do
           __evaluate__(statements, file, line)
-        ensure
-          Tracer.off
         end
       else
-        __evaluate__(statements, file || __FILE__, line || __LINE__)
+        __evaluate__(statements, file, line)
       end
     end
   end
-
-  IRB.initialize_tracer
 end

lib/irb/extend-command.rb

@@ -317,7 +317,6 @@ module ContextExtender
 
     @EXTEND_COMMANDS = [
       [:eval_history=, "ext/eval_history.rb"],
-      [:use_tracer=, "ext/tracer.rb"],
       [:use_loader=, "ext/use-loader.rb"],
     ]
 

test/irb/test_context.rb

@@ -1,7 +1,7 @@
 # frozen_string_literal: false
 require 'tempfile'
 require 'irb'
-require 'rubygems' if defined?(Gem)
+require 'rubygems'
 
 require_relative "helper"
 

test/irb/test_init.rb

@@ -216,6 +216,12 @@ def test_dash
       assert_equal(['-f'], argv)
     end
 
+    def test_option_tracer
+      argv = %w[--tracer]
+      IRB.setup(eval("__FILE__"), argv: argv)
+      assert_equal(true, IRB.conf[:USE_TRACER])
+    end
+
     private
 
     def with_argv(argv)

test/irb/test_tracer.rb

@@ -0,0 +1,97 @@
+# frozen_string_literal: false
+require 'tempfile'
+require 'irb'
+require 'rubygems'
+
+require_relative "helper"
+
+module TestIRB
+  class ContextWithTracerIntegrationTest < IntegrationTestCase
+    def setup
+      super
+
+      @envs.merge!("NO_COLOR" => "true", "RUBY_DEBUG_HISTORY_FILE" => '')
+    end
+
+    def example_ruby_file
+      <<~'RUBY'
+        class Foo
+          def self.foo
+            100
+          end
+        end
+
+        def bar(obj)
+          obj.foo
+        end
+
+        binding.irb
+      RUBY
+    end
+
+    def test_use_tracer_is_disabled_by_default
+      write_rc <<~RUBY
+        IRB.conf[:USE_TRACER] = false
+      RUBY
+
+      write_ruby example_ruby_file
+
+      output = run_ruby_file do
+        type "bar(Foo)"
+        type "exit!"
+      end
+
+      assert_nil IRB.conf[:USER_TRACER]
+      assert_not_include(output, "#depth:")
+      assert_not_include(output, "Foo.foo")
+    end
+
+    def test_use_tracer_enabled_when_gem_is_unavailable
+      begin
+        gem 'tracer'
+        omit "Skipping because 'tracer' gem is available."
+      rescue Gem::LoadError
+        write_rc <<~RUBY
+          IRB.conf[:USE_TRACER] = true
+        RUBY
+
+        write_ruby example_ruby_file
+
+        output = run_ruby_file do
+          type "bar(Foo)"
+          type "exit!"
+        end
+
+        assert_include(output, "Tracer extension of IRB is enabled but tracer gem wasn't found.")
+      end
+    end
+
+    def test_use_tracer_enabled_when_gem_is_available
+      if Gem::Version.new(RUBY_VERSION) < Gem::Version.new('3.1.0')
+        omit "Ruby version before 3.1.0 does not support Tracer integration. Skipping this test."
+      end
+
+      begin
+        gem 'tracer'
+      rescue Gem::LoadError
+        omit "Skipping because 'tracer' gem is not available. Enable with WITH_TRACER=true."
+      end
+
+      write_rc <<~RUBY
+        IRB.conf[:USE_TRACER] = true
+      RUBY
+
+      write_ruby example_ruby_file
+
+      output = run_ruby_file do
+        type "bar(Foo)"
+        type "exit!"
+      end
+
+      assert_include(output, "Object#bar at")
+      assert_include(output, "Foo.foo at")
+      assert_include(output, "Foo.foo #=> 100")
+      assert_include(output, "Object#bar #=> 100")
+    end
+  end
+end