From: Robert Klemme <shortcutter@...>
Date: 2011-06-14T18:53:40+09:00
Subject: Re: A way to find out when a constant gets defined?

On Tue, Jun 14, 2011 at 11:32 AM, Josh Cheek <josh.cheek@gmail.com> wrote:
> Hi, I'd like to be able to find out when a constant gets defined. I think I
> have a gem that vendored Psych, so it doesn't get listed in my dependencies,
> but causes the most unusual and difficult to track bugs (because other
> things, like rake tasks that don't load the entire environment, don't get
> Psych loaded, and thus behave differently when doing things like serializing
> data).
>
>
> Here is my reasoning:
>
> # I do not even have psych installed (it isn't listed)
> $ gem list psych
>
> *** LOCAL GEMS ***
>
>
> # Psych is not a dependency (no output)
> $ cat Gemfile.lock | grep -i psych
>
>
> # When I load irb with my app, Psych is somehow defined
> $ bundle exec irb
> ruby-1.9.2-p180 :001 > Psych
>  => Psych
> ruby-1.9.2-p180 :002 > exit
>
>
> # When I load irb without my app, Psych is not defined
> $ irb
> ruby-1.9.2-p180 :001 > Psych
> NameError: uninitialized constant Object::Psych
> from (irb):1
> from /Users/josh/.rvm/rubies/ruby-1.9.2-p180/bin/irb:16:in `<main>'
> ruby-1.9.2-p180 :002 > exit
>
>
> # For each file in my dir, exempting files in ./git, list the lines matching
> /psych/i
> # prints nothing, so Psych is not coming from my code.
> $ find . -name \* | ruby -ne 'puts $_ unless /^\.\/\.git/' | xargs grep -i
> psych
>
>
>
> I don't really know what to do, I tried `$ bundle package` and then
> untarring and gunzipping all the gems, and then grepping them for it, but
> didn't find anything. I can't figure out where this is coming from, so I'd
> like to be able to monitor the constant Psych to find out when it gets set.

These options come to mind:

Define constant Psych yourself before any requires and watch out for
the warning "already initialized constant" which also mentions file
and line number.

Use set_trace_func lambda {|*a| p a} before the first require and try
to see whether you can find out from there psych code is loaded.

$ find /c/Archives/ruby-lang.org/ruby-1.9.2-p180 -name '*.[ch]' |
xargs fgrep -nw Psych
/c/Archives/ruby-lang.org/ruby-1.9.2-p180/ext/psych/emitter.c:36:/*
call-seq: Psych::Emitter.new(io)
/c/Archives/ruby-lang.org/ruby-1.9.2-p180/ext/psych/emitter.c:38: *
Create a new Psych::Emitter that writes to +io+.
/c/Archives/ruby-lang.org/ruby-1.9.2-p180/ext/psych/emitter.c:54: *
See Psych::Handler#start_stream
/c/Archives/ruby-lang.org/ruby-1.9.2-p180/ext/psych/emitter.c:74: *
See Psych::Handler#end_stream
/c/Archives/ruby-lang.org/ruby-1.9.2-p180/ext/psych/emitter.c:94: *
See Psych::Handler#start_document
/c/Archives/ruby-lang.org/ruby-1.9.2-p180/ext/psych/emitter.c:159: *
See Psych::Handler#end_document
/c/Archives/ruby-lang.org/ruby-1.9.2-p180/ext/psych/emitter.c:179: *
See Psych::Handler#scalar
/c/Archives/ruby-lang.org/ruby-1.9.2-p180/ext/psych/emitter.c:217: *
See Psych::Handler#start_sequence
/c/Archives/ruby-lang.org/ruby-1.9.2-p180/ext/psych/emitter.c:247: *
See Psych::Handler#end_sequence
/c/Archives/ruby-lang.org/ruby-1.9.2-p180/ext/psych/emitter.c:267: *
See Psych::Handler#start_mapping
/c/Archives/ruby-lang.org/ruby-1.9.2-p180/ext/psych/emitter.c:297: *
See Psych::Handler#end_mapping
/c/Archives/ruby-lang.org/ruby-1.9.2-p180/ext/psych/emitter.c:316: *
See Psych::Handler#alias
/c/Archives/ruby-lang.org/ruby-1.9.2-p180/ext/psych/emitter.c:388:
VALUE psych     = rb_define_module("Psych");
/c/Archives/ruby-lang.org/ruby-1.9.2-p180/ext/psych/parser.c:49: * See
Psych::Parser and Psych::Parser#handler
/c/Archives/ruby-lang.org/ruby-1.9.2-p180/ext/psych/parser.c:292:
mPsych = rb_define_module("Psych");
/c/Archives/ruby-lang.org/ruby-1.9.2-p180/ext/psych/psych.c:3:/*
call-seq: Psych.libyaml_version
/c/Archives/ruby-lang.org/ruby-1.9.2-p180/ext/psych/psych.c:25:
mPsych = rb_define_module("Psych");
/c/Archives/ruby-lang.org/ruby-1.9.2-p180/ext/psych/to_ruby.c:33:
VALUE psych     = rb_define_module("Psych");
/c/Archives/ruby-lang.org/ruby-1.9.2-p180/ext/psych/yaml_tree.c:17:
VALUE psych     = rb_define_module("Psych");

:-)

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/