[ruby/irb] Reduce internal operations' exposure to benchmarking

(https://github.com/ruby/irb/pull/618)

* Test last value is assigned with measure enabled

* Remove unnecessary `result` variable

`Context#evaluate` always assigns the result of the evaluation to `_` so
we don't need to do it in `Irb#eval_input`.

* Move benchmarking logic into `Context#evaluate`

Current location of the benchmarking logic is too high up and includes
operations like command loading and argument transformation, which should
be excluded. So this commit moves it into `Context#evaluate` to reduce the
noise.

We don't move it further down to `Workspace#evaluate` because `Context`
is an argument of the measure block, which is not available in `Workspace`.

1 files changed, 23 insertions, 1 deletions

diff --git a/lib/irb/context.rb b/lib/irb/context.rb
index 58964aa832..6f209b596a 100644
--- a/lib/irb/context.rb
+++ b/lib/irb/context.rb
@@ -475,7 +475,29 @@ module IRB
 
     def evaluate(line, line_no) # :nodoc:
       @line_no = line_no
-      set_last_value(@workspace.evaluate(line, irb_path, line_no))
+      result = nil
+
+      if IRB.conf[:MEASURE] && IRB.conf[:MEASURE_CALLBACKS].empty?
+        IRB.set_measure_callback
+      end
+
+      if IRB.conf[:MEASURE] && !IRB.conf[:MEASURE_CALLBACKS].empty?
+        last_proc = proc do
+          result = @workspace.evaluate(line, irb_path, line_no)
+        end
+        IRB.conf[:MEASURE_CALLBACKS].inject(last_proc) do |chain, item|
+          _name, callback, arg = item
+          proc do
+            callback.(self, line, line_no, arg) do
+              chain.call
+            end
+          end
+        end.call
+      else
+        result = @workspace.evaluate(line, irb_path, line_no)
+      end
+
+      set_last_value(result)
     end
 
     def inspect_last_value # :nodoc: