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https://github.com/viralpraxis/purist
Automatic runtime impure ruby methods invocation detection
https://github.com/viralpraxis/purist
functional-programming purity rspec ruby testing
Last synced: 18 days ago
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Automatic runtime impure ruby methods invocation detection
- Host: GitHub
- URL: https://github.com/viralpraxis/purist
- Owner: viralpraxis
- License: mit
- Created: 2024-03-04T20:31:32.000Z (9 months ago)
- Default Branch: main
- Last Pushed: 2024-03-10T14:23:15.000Z (8 months ago)
- Last Synced: 2024-10-09T10:44:55.953Z (about 1 month ago)
- Topics: functional-programming, purity, rspec, ruby, testing
- Language: Ruby
- Homepage:
- Size: 15.6 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE.txt
- Code of conduct: CODE_OF_CONDUCT.md
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README
# Purst
Purist is a tool designed to help detecting impure ruby code in runtime.
Ruby's stdlib and corelibs include a bunch of impure methods, including
1. randomization: `Kernel.rand`, `Random.rand`, `SecureRandom.hex` and so on
2. IO-related methods like `Kernel.readline` or `IO.popen`
3. specialized side-effects like `Kernel.fork` or `Kernel.syscall`
Purist hooks into ruby's `tracepoint` API to detect any invocation of these methods.
You can see the full list of target methods in `configuration.rb` source file.
## Installation
Install the gem and add to the application's Gemfile by executing:
$ bundle add purist
If bundler is not being used to manage dependencies, install the gem by executing:
$ gem install purist
## Usage
To check if your code is pure, simply pass it into `Purist.trace` method:
```ruby
Purist.trace { 3 * 3 } # 9
```
If provided block is impure, an exception will be raised:
```ruby
irb(main):001> Purist.trace { p "I'm impure" }
gems/purist/lib/purist/handler.rb:23:in `call': {:path=>"(irb)", :lineno=>1, :module_name=>Kernel, :method_name=>:p} (Purist::Errors::PurityViolationError)
```
You can retrieve exception details like this:
```ruby
exception = Purist.trace { p 1 } rescue $!
p exception.trace_point
{
:path => ".../zeitwerk-2.6.13/lib/zeitwerk/kernel.rb",
:lineno => 23,
:module_name => Kernel,
:method_name => :require,
:backtrace => [...]
}
```
### RSpec integration
Purist comes with built-in `RSpec` integration. To enable it, add `require "purist/integrations/rspec"` to your
`spec_helper.rb` and manually include `Purist::Integrations::RSpec::Matchers`:
```ruby
require "purist/integrations/rspec"
...
RSpec.configure do |config|
...
config.include Purist::Integrations::RSpec::Matchers
...
end
```
And not `be_pure` and `be_impure` matchers are available:
```ruby
expect { Module.new }.to be_pure
expect { User.where(name: :john) }.to be_impure
```
### Caveats
1. Passing `Purist.trace` check does not mean your function is totally pure, for instance
```ruby
def foo(n)
if n > 0 # pure branch
n.succ
else # impure branch
p n
end
end
Purist.trace { foo(3) } # 4
```
2. Ruby stdlib/corelib is quite big, I'm pretty sure some impure functions are missing from the list.
3. Obviously, Purist is unable to detect anything within 3rd-party C extensions.
## 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 the created tag, and push the `.gem` file to [rubygems.org](https://rubygems.org).
## Contributing
Bug reports and pull requests are welcome on GitHub at https://github.com/viralpraxis/purist. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the [code of conduct](https://github.com/viralpraxis/purist/blob/main/CODE_OF_CONDUCT.md).
## License
The gem is available as open source under the terms of the [MIT License](https://opensource.org/licenses/MIT).
## Code of Conduct
Everyone interacting in the Purist project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the [code of conduct](https://github.com/viralpraxis/purist/blob/main/CODE_OF_CONDUCT.md).