README.md
# Loba
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Easy tracing for debugging: handy methods for adding trace lines to output (or Rails 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)?
1. 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 not have any (much) more impact than regular `puts` or `Rails.logger.debug` statements.
Loba statements are expected to be removed when you're done with them. No point in cluttering up production code.
Loba will always write to STDOUT (i.e., `puts`).
Loba will work equally well with or without Rails. If Rails is present, in addition to STDOUT, Loba can also be made to write to `Rails.logger.debug`.
Loba uses the [rainbow gem](https://rubygems.org/gems/rainbow) to help make trace statements more visible.
## Usage
My advice is to align Loba statements to the far left in your source code (a la `=begin` or `=end`) so they're easy to see and remove when you're done.
#### 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](http://ruby-doc.org/core-2.2.3/Kernel.html#method-i-set_trace_func). Also does a simple elapsed time check since the previous timestamp notice to help with quick, minimalist profiling.
For example,
```text
[TIMESTAMP] #=0002, diff=93.478016, at=1451444972.970602 (in=/home/usracct/src/myapp/app/models/target.rb:55:in `some_calculation')
```
To invoke,
```ruby
Loba.ts # or with optional keyword arguments
```
`Loba.timestamp` is an alias for `Loba.ts`.
You can read [more detail](readme/ts.md) on this command.
#### Variable or method return inspection: `Loba.val`
Writes line to STDOUT (or optionally to Rails.logger.debug if available) showing value with method and class identification.
```ruby
Loba.val :var_sym # the :var_sym argument is the variable or method name given as a symbol
```
For example,
```text
[Target.some_calculation] my_var: 54 (in /home/usracct/src/myapp/app/models/target.rb:55:in `some_calculation')
```
You can read [more detail](readme/val.md) on this command.
#### Snippet example
```ruby
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:
```text
[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 options hash with `:production => true` as an additional last 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 be avoided, but we're consenting adults.
WARNING: this gem depends on the [binding_of_caller gem](https://rubygems.org/gems/binding_of_caller) -- 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's usually 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 those statements to 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:
```ruby
class HelloWorld
def initialize
@x = 42
Loba.ts production: true
@y = "Charlie"
end
def hello
Loba.val :@x, 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):
```bash
gem install loba
```
To bundle, add this line to your application's Gemfile:
```ruby
group :development, :test do
gem 'loba', require: false
end
```
or for all environments (for example, if `production: true` used):
```ruby
gem 'loba', require: false
```
And then execute:
```bash
bundle
```
## 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](https://rubygems.org).
## Changelog
See [CHANGELOG.md](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](http://contributor-covenant.org) code of conduct.
## License
The gem is available as open source under the terms of the [MIT License](http://opensource.org/licenses/MIT).