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Bug #16383

closed

TracePoint does not report calls to attribute reader methods

Added by AndyMaleh (Andy Maleh) over 4 years ago. Updated over 2 years ago.

Status:
Closed
Assignee:
-
Target version:
-
ruby -v:
ruby 2.5.7p206 (2019-10-01 revision 67816) [x86_64-darwin19]
[ruby-core:96032]

Description

TracePoint does not report calls to attribute reader methods (e.g. methods defined using attr_accessor or attr_reader.)

Code sample to demonstrate:

class Person
  attr_accessor :first_name
  attr_accessor :last_name
  def name
    "#{self.last_name}, #{self.first_name}"
  end
end

person = Person.new
person.first_name = 'Josh'
person.last_name = 'McGibbon'
trace = TracePoint.new(:call) do |tp|
  p [tp.path, tp.lineno, tp.defined_class, tp.event, tp.method_id]
end
trace.enable
person.name
trace.disable

class Person
  attr_writer :first_name
  attr_writer :last_name
  def name
    "#{self.last_name}, #{self.first_name}"
  end
  def first_name
    @first_name
  end
  def last_name
    @last_name
  end
end

person = Person.new
person.first_name = 'Josh'
person.last_name = 'McGibbon'
trace = TracePoint.new(:call) do |tp|
  p [tp.path, tp.lineno, tp.defined_class, tp.event, tp.method_id]
end
trace.enable
person.name
trace.disable

Output:

["trace_point_issue.rb", 4, Person, :call, :name]
["trace_point_issue.rb", 22, Person, :call, :name]
["trace_point_issue.rb", 28, Person, :call, :last_name]
["trace_point_issue.rb", 25, Person, :call, :first_name]

Please note how :last_name and :first_name show up only the second time Person#name is called. In other words, they show up when defined as actual methods using def keyword, but not when defined via attr_accessor.

Expected Output:

["trace_point_issue.rb", 22, Person, :call, :name]
["trace_point_issue.rb", 28, Person, :call, :last_name]
["trace_point_issue.rb", 25, Person, :call, :first_name]
["trace_point_issue.rb", 22, Person, :call, :name]
["trace_point_issue.rb", 28, Person, :call, :last_name]
["trace_point_issue.rb", 25, Person, :call, :first_name]

Your help in fixing or explaining this issue is greatly appreciated.

My goal is to monitor all method calls when invoking a certain method (Person#name in this case) in order to attach observers to them dynamically for desktop UI data-binding use in my open-source project Glimmer: https://github.com/AndyObtiva/glimmer

Cheers,

Andy Maleh


Files

trace_point_issue.rb (791 Bytes) trace_point_issue.rb contains code sample to demonstrate issue AndyMaleh (Andy Maleh), 11/30/2019 03:16 AM
tracepoint-attr-16383.patch (1.97 KB) tracepoint-attr-16383.patch jeremyevans0 (Jeremy Evans), 12/04/2019 12:42 AM

Related issues 2 (0 open2 closed)

Related to Ruby master - Bug #10470: TracePoint cannot trace attr_accessor/reader/writer methodClosedko1 (Koichi Sasada)Actions
Related to Ruby master - Bug #18886: Struct aref and aset don't trigger any tracepoints.Closedko1 (Koichi Sasada)Actions
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