Class: SimpleCov::TestTracker::ConstantWatch

Inherits:
Module
  • Object
show all
Defined in:
lib/simplecov/test_tracker/constant_watch.rb

Overview

A one-shot watch that runs a callback the moment a constant of a given name is defined under a host module, via Ruby's Module#const_added. TestTracker uses it to install the Minitest wrapper in the ordering minitest 6 abandoned plugins for: SimpleCov starts first, as coverage must to see the app load, and minitest is required later, so nothing of minitest's exists yet to hook into.

Each watch is its own Module so it can be prepended to the host's singleton class and compose with any const_added the host already has. A prepend cannot be removed, so after firing the watch stays in place as a name comparison per constant definition, which is as close to free as Ruby gets.

Instance Method Summary collapse

Constructor Details

#initialize(name, &on_added) ⇒ ConstantWatch

No super: it would forward the implicit block even given explicit arguments, and Module#initialize module_evals any block it gets.



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# File 'lib/simplecov/test_tracker/constant_watch.rb', line 19

def initialize(name, &on_added)
  @name = name
  @on_added = on_added
  watch = self #: ConstantWatch
  define_method(:const_added) do |added|
    super(added) # steep:ignore UnexpectedPositionalArgument
    watch.notice(added)
  end
end

Instance Method Details

#attach(host) ⇒ Object

host.const_added runs with the host as self, so reaching this watch's state takes the closure. At runtime the super inside is the host's next const_added; Steep resolves a define_method block's super against the lexically enclosing method instead.



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# File 'lib/simplecov/test_tracker/constant_watch.rb', line 33

def attach(host)
  host.singleton_class.prepend(self)
  self
end

#notice(added) ⇒ Object 



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# File 'lib/simplecov/test_tracker/constant_watch.rb', line 38

def notice(added)
  return unless added.equal?(@name)

  callback = @on_added
  return unless callback

  @on_added = nil
  callback.call
end