Loba

Easy tracing for debugging: handy methods for adding trace lines to output (or logs).

(Installation is pretty much what you'd expect for a gem, but read Environment Notes below first.)

Overview

There are two kinds of questions I usually want to answer when trying to diagnose code behavior:

1. Is this spot of code being reached (or is it reached in the order I think it is)?
2. What is the value of this variable?

Loba statements are intended to be terse to minimize typing.

Loba statements are intended to be minimally invasive and atomic. They should have negligible impact over regular puts or logging statements.

Loba statements are expected to be removed when you're done with them. No point in cluttering up production code.

Loba will generally always write to $stdout (i.e., puts). In addition to $stdout, Loba can also be made to write to a log (:debug). Writing to $stdout can be overridden.

Loba will work equally well with or without Rails. If Rails is present and writing to a log is wanted, it will use the Rails log (e.g., Rails.logger.debug).

Loba uses the rainbow gem to help make trace statements more visible.

Usage

Aligning Loba statements to the far left in your source code (a la =begin or =end) will make them easier to see and remove when you're done. You may though find this somewhat annoying to do if your editor auto-indents.

Timestamp notices: Loba.ts

Outputs a timestamped notice, useful for quick traces to see the code path and easier than, say, Kernel#set_trace_func. Also does a simple elapsed time check since the previous timestamp notice to help with quick, minimalist profiling.

For example,

[TIMESTAMP] #=0002, diff=93.478016, at=1451444972.970602     (in=/home/usracct/src/myapp/app/models/target.rb:55:in `some_calculation')

To invoke,

Loba.ts    # or with optional keyword arguments

Loba.timestamp is an alias for Loba.ts.

You can read more detail on this command.

Variable or method return inspection: Loba.val

Writes line to $stdout (or optionally to a log, logger.debug) showing value with method and class identification.

Loba.val :var_sym   # the :var_sym argument is the variable or method name given as a symbol

For example,

[Target.some_calculation] my_var: 54       (in /home/usracct/src/myapp/app/models/target.rb:55:in `some_calculation')

You can read more detail on this command.

Output and logging options

There are several options to control where Loba writes its output:

• out: controls whether puts to $stdout occurs (default: true)
• log: controls whether logging occurs (default: false)
• logger: controls which logger is used
• logdev: in non-Rails environments, another way to direct where logging occurs

You can read more detail about how to use these options.

Snippet example

require 'loba'    # not generally necessary in Rails projects
class HelloWorld
  def initialize
    @x = 42
Loba.ts          # Loba statement put to the far left as a reminder to remove when done
    @y = "Charlie"
  end

  def hello
Loba.val :@x
    puts "Hello, #{@y}" if @x == 42
Loba.ts
  end
end
HelloWorld.new.hello

Output:

[TIMESTAMP] #=0001, diff=0.000463, at=1451615389.505411   (in=/home/usracct/src/lobademo/hello_world.rb:4:in 'initialize'
[HelloWorld#hello] @x: 42       (in /home/usracct/src/loba/spec/hello_world.rb:9:in `hello')
Hello, Charlie
[TIMESTAMP] #=0002, diff=0.000720, at=1451615389.506132   (in=/home/usracct/src/lobademo/hello_world.rb:11:in 'hello'

Environment Notes

This section is only relevant in Rails environments.

The expectation is that Loba statements are just for development or test trace statements. Generally, it's a bad idea to leave diagnostic code in Rails production; still, it can happen. And, occasionally, it can be useful to have trace statements in production too if you have an issue that is difficult to reproduce.

Loba.ts and Loba.val try to protect against timestamp or value notice requests being accidentally left in the code by checking for the Rails environment Loba is being invoked under. If in production, Loba.ts and Loba.val will normally just return immediately without attempting to render anything to help minimize any impact on production code.

However, that behavior can be overridden by using the option production: true as an additional argument to output a notice even when in the production environment. Note also behavior of the log option, which defaults to false (introduced in v2.0.0). In general, enabling in production should not be done, but we're consenting adults.

WARNING: this gem depends on the binding_of_caller gem -- use production: true with their warning in mind:

Recommended for use only in debugging situations. Do not use this in production apps.

These considerations also have an impact on how you install the Loba gem when using bundler. If you only install the gem for :development and :test, then any Loba statements left in the code when it goes to production will cause an error because the statements wouldn't be recognized. That can be a good thing if you never want them left in.

If you simply install the gem for all environments, then Loba will be available in production, but you may not notice as easily if some Loba calls are unintentionally left in. Of course, if you want Loba statements to possibly work in production, then you should install the gem for all environments.

The following is the code example snippet but always logging even in Rails production environments:

class HelloWorld
  def initialize
    @x = 42
Loba.ts log: true, production: true
    @y = "Charlie"
  end

  def hello
Loba.val :@x, log: true, production: true
    puts "Hello, #{@y}" if @x == 42
Loba.ts true
  end
end
HelloWorld.new.hello

Installation

See above Environment Notes if using with Rails.

Install as below to be generally available (recommended to restrict to only local use):

gem install loba

To bundle, add this line to your application's Gemfile:

group :development, :test do
  gem 'loba', require: false
end

or for all environments (for example, if production: true used):

gem 'loba', require: false

And then execute:

bundle install

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install.

To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Changelog

See CHANGELOG.md for details. This gem follows semantic versioning.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/rdnewman/loba. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The gem is available as open source under the terms of the MIT License.