Starting Byebug with a block - ruby-on-rails

I'm wondering if it's possible to start a Byebug session giving a starting point from a Rails console. I know I can insert a byebug statement wherever I want and start debugging, but I'd like to do something like this:
Byebug.start do
# entry point
User.find(12).problematic_method
end
Thanks.

I opened the class and override the problematic_method inside the Rails console and added the byebug statement where I wanted it. This way I don't have to change the running production code (I forgot to mention above I want to debug in production).
This workaround will be enough for my purposes. The only problem is that you don't have the debug code listing available for that method, but its fine.

That is not possible. What you can do, is write your code inside a .rb file and debug that file/script using byebug.

Related

Make Byebug finish executing without exiting Pry

When I set a breakpoint with Byebug in Rails, I sometimes want it to finish executing, but the guide on github says to use exit which also exits Pry. Typing continue repeatedly can be annoying if the breakpoint is in a loop.
Is there anyway to stop byebug without exiting the Rails console?
When running byebug under the Rails console or in Rails' server I usually quit only byebug by hitting Ctrl+D.
The catch with this approach is, if you do this in Rails' server then Byebug will not stop and debug the next time it hits a byebug statement in your code anywhere. But it works perfectly in the Rails console.
Try !!!. It works on pry gem, but not sure if it does on byebug.
Well this isn't the most elegant solution but it works for me so far.
If you have a base controller in your rails application you can add an accessor to hold a variable saying whether you want debugging to happen or not:
attr_accessor :debugging
Then add/modify initializer to set the variable to true on each request (or each time there is an instance created for that object):
def initialize
#debugging=true
super
end
And finally, always use the byebug call with a conditional wherever you want this behavior:
byebug if debugging
Then when you are at the IRB console and you want to exit the debugger but continue executing the code you just set the variable:
#debugging=false; finish
You could even encapsulate this in a helper or do some OOP magic but this is a good starting point. Nice thing is that if you repeat the request you'll get the standard behavior again unless you set the variable to false again.
If you want to exit a loop try skip.
It'll runs until the next breakpoint as long as it is different from the current one.
Then, once you are out of the loop you can continue.
Typing finish in the console exits byebug, without closing pry/rails console/rails server.
Ctrl + D also works.
Go to your code and remove byebug and save, then in the buybug terminal write continue then press enter.
Tadaaa your app will continue and you will exit byebug all without closing your app.
Try continue or finish
Source: https://edgeguides.rubyonrails.org/debugging_rails_applications.html#resuming-execution
Remove "debugger from your code and type in "finish" in console
(byebug) quit
Really quit? (y/n) y
user ~
The only one that works quickly and without issues for me so far.

Why do ActiveRecord queries from console print sql statements?

I'm using pry, and ActiveRecord queries from the console always print out their corresponding SQL statements. I don't want this behavior. Googling around I only see that this must be explicitly achieved by setting the ActiveRecord logger to standard out.
Is this the default behavior of pry or is it the result of something I set that I forgot about? And how can I stop it?
Try looking for a .irbrc file in the project root or your home directory. You may see this or similar:
ActiveRecord::Base.logger = Logger.new(STDOUT)
Sometimes this ends up in another script that gets included in .irbrc.
YMMV, but I really like having SQL logged to the console. To each his own...
If you are using Rails 3.1+ this is now the default behaviour. Check here Disable Rails SQL logging in console

Debugging/Breakpoint-ing the Rails Core with Ruby-Debug?

How do I debug the rails gems? I've just found the beauty of ruby-debug and am real excited, but I want to step through the routing code in action_controller, but the debugger isn't set up at this time, it seems like it's just skipping over my "debugger" calls in action_controller/routing/route_set.rb for example.
What am I missing?
I just tested this with Rails 2.3.4. I added a 'debugger' line to the call method in vendor/rails/actionpack/lib/action_controller/routing/route_set.rb, ran 'rdebug script/server', browsed to a page, and it stopped at the correct line.
You can also use a class/method breakpoint; you'll need to step through the first few lines of the app until you're past the require 'action_controller' line, and then enter: b ActionController::Routing::RouteSet.call.
Or you can try setting a breakpoint based on the file name and line number.

How do I use a custom log for my rake tasks in Ruby on Rails?

I have a rake task that calls functions like this:
namespace :blah do
task :hello_world => :environment do
logger.info("Hello World")
helloworld2
end
end
def helloworld2
logger.info("Hello Again, World")
end
I want the log output to a custom log, and I really don't want to have to pass a log reference every time I make a function call. I found this somewhere (can't find it again):
def logger
##logger ||= Logger.new("#{RAILS_HOME}/log/blah.log")
end
But this does not work for me and I am not sure what it even does because I grabbed the code a long time ago and haven't used it until now. I can't search for ## on google (tried +"##" rails) to see what it does. Any help on this issue would be great. I am hoping for a quick solution and not having to install a gem or plugin (unless there is a really really good reason to.
Thanks!
rake disables logging in production mode. make sure you're running in development mode if you want it to log
What do you mean by "does not work for me"? I just tried this same code and it worked - created a new log file and put some text in it.
##logger is a class variable, it's a language issue, not Rails' one. I believe there's no need in further explanations :)
You've probably mistaken typing "function helloworld2" :)
Advanced Rails Recipes Recipe 84 from #topfunky shows how to define a custom logger. He has some code in the environment config file (production would look like this): RAILS_ROOT/config/environments/production.rb:
config.logger = RAILS_DEFAULT_LOGGER = Logger.new(config.log_path)
I'd test that out instead of redefining the class variable as you have. He might have something on http://nubyonrails.com to check as well.

How to determine the value of a controller variable during execution in Ruby on Rails?

What is the best way for me to determine a controller variable's value during execution?
For example, is there a way I can insert a break in the code, and cause the value of the variable to be output to the screen (or the log)?
Yes. The easiest way is to raise the value as a string. Like so: raise #foo.to_s
Or, you can install the debugger (gem install ruby-debug), and then start the development server with the --debugger flag. Then, in your code, call the debugger instruction.
Inside the debugger prompt, you have many commands, including p to print the value of a variable.
Update: here's a bit more about ruby-debug.
If you have a controller instance variable named #foo, then in your controller you can simply do something like:
logger.debug "#foo is: #{#foo}"
Additionally, you can output the value in your view template using:
<%= debug #foo %>
I prefer using the inspect method like so:
raise #foo.inspect
It has more information than to_s, like the attribute values.
Summary from Jordi Bunster, John Topley, and Jaryl:
I. Quick and dirty way:
raise #foo.inspect
in your controller. Or
<% raise #foo.inspect %>
in your view.
II. Proper logging to you development.log:
logger.debug "#foo == #{#foo.inspect}"
III. Full-fledged debugging:
Install the debugger (gem install ruby-debug), and then start the development server with the --debugger flag. Then, in your code, call the debugger instruction.
Inside the debugger prompt, you have many commands, including p to print the value of a variable.
Raising an exception is the fastest way if you just need to look at a value, but it's worth the time to learn how to use the debugger properly. It's rare that you would only need to just see the value of a variable, you are likely trying to find a bug in your code, and that's what a debugger is for.
Sending the info to the development log is slower than either of the other two options here so far if you learn how to use the debugger (who wants to read through log files). Use the logger for production, you are going to want to see what the value was when somebody calls you up and says everything is broken.
Well, I usually prefer the standard error output
$stderr.print("whatever")
Its simple and does the job.
Add pry-moves to Gemfile: gem 'pry-moves'
Insert binding.pry where you want to stop
Type variable's name to see its value
Then continue by typing c, move to next line with n or perform other debugging actions until you will resolve the issue.

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