Support TappingDevice::Device#stop_when

lib/tapping_device/device.rb

@@ -1,8 +1,10 @@
 require "active_record"
+require "tapping_device/exceptions"
 
 module TappingDevice
   class Device
     CALLER_START_POINT = 2
+    FORCE_STOP_WHEN_MESSAGE = "You must set stop_when condition before start tapping"
 
     attr_reader :options, :calls
 
@@ -26,6 +28,21 @@ def tap_assoc!(record)
       track(record, condition: :tap_associations?, block: @block, **@options)
     end
 
+    def tap_init(klass)
+      validate_tapping(__method__)
+      tap_init!(klass)
+    end
+
+    def tap_on(object)
+      validate_tapping(__method__)
+      tap_on!(object)
+    end
+
+    def tap_assoc(record)
+      validate_tapping(__method__)
+      tap_assoc!(record)
+    end
+
     def set_block(&block)
       @block = block
     end
@@ -34,9 +51,24 @@ def stop!
       @trace_point.disable if @trace_point
     end
 
+    def stop_when(&block)
+      @stop_when = block
+    end
+
     private
 
+    def validate_tapping(method_name)
+      unless @stop_when
+        raise TappingDevice::Exception.new <<~ERROR
+          You must set stop_when condition before calling #{method_name}. Or you can use #{method_name}! to force tapping.
+          Tapping without stop condition can largely slow down or even halt your application, because it'll need to
+          screen literally every call happened.
+        ERROR
+      end
+    end
+
     def track(object, condition:, block:, with_trace_to: nil, exclude_by_paths: [], filter_by_paths: nil)
+
       @trace_point = TracePoint.trace(:return) do |tp|
         filepath, line_number = caller(CALLER_START_POINT).first.split(":")[0..1]
 
@@ -70,6 +102,8 @@ def track(object, condition:, block:, with_trace_to: nil, exclude_by_paths: [],
             @calls << yield_parameters
           end
         end
+
+        stop! if @stop_when&.call(yield_parameters)
       end
 
       self

lib/tapping_device/exceptions.rb

@@ -0,0 +1,4 @@
+module TappingDevice
+  class Exception < StandardError
+  end
+end

spec/performance_spec.rb

@@ -0,0 +1,51 @@
+require "spec_helper"
+require 'benchmark'
+
+RSpec.describe TappingDevice::Device do
+  let(:devices) do
+    devices = []
+    100.times { devices << TappingDevice::Device.new }
+    devices
+  end
+
+  after do
+    devices.each(&:stop!)
+  end
+
+  context "without stop_when" do
+    it "takes long time when tapping multiple devices" do
+      time = Benchmark.realtime do
+        devices.each do |device|
+          s = Student.new("foo", 10)
+          device.tap_on!(s)
+          10.times { s.name }
+
+          expect(device.calls.count).to eq(10)
+        end
+      end
+      devices.each { |d| d.stop! }
+      expect(time).to be_between(4, 10)
+    end
+  end
+
+  context "with stop_when" do
+    it "takes very short time when tapping multiple devices" do
+      time = Benchmark.realtime do
+        devices.each do |device|
+          device.stop_when do
+            device.calls.count == 10
+          end
+
+          s = Student.new("foo", 10)
+          device.tap_on!(s)
+          10.times { s.name }
+
+          expect(device.calls.count).to eq(10)
+        end
+      end
+
+      devices.each { |d| d.stop! }
+      expect(time).to be_between(0, 1)
+    end
+  end
+end

spec/tapping_device_spec.rb

@@ -200,4 +200,49 @@
       expect(count).to eq(1)
     end
   end
+
+  describe "#tap_init" do
+    let(:device) { TappingDevice::Device.new }
+    let(:stan) { Student.new("stan", 25) }
+
+    it "raises error if device has no stop_when set" do
+      expect { device.tap_init(Student) }.to raise_error(TappingDevice::Exception)
+    end
+  end
+
+  describe "#tap_on" do
+    let(:device) { TappingDevice::Device.new }
+    let(:stan) { Student.new("stan", 25) }
+
+    it "raises error if device has no stop_when set" do
+      expect { device.tap_on(stan) }.to raise_error(TappingDevice::Exception)
+    end
+  end
+
+  describe "#tap_assoc" do
+    let(:device) { TappingDevice::Device.new }
+    let(:post) { Post.new }
+
+    it "raises error if device has no stop_when set" do
+      expect { device.tap_assoc(post) }.to raise_error(TappingDevice::Exception)
+    end
+  end
+
+  describe "#stop_when" do
+    it "stops tapping once fulfill stop_when condition" do
+      device = TappingDevice::Device.new
+      device.stop_when do |payload|
+        device.calls.count == 10
+      end
+
+      s = Student.new("foo#", 10)
+      device.tap_on!(s)
+
+      100.times do
+        s.name
+      end
+
+      expect(device.calls.count).to eq(10)
+    end
+  end
 end