Class: RubyTransform::Transformers::Tapifier

Inherits:
RubyTransform::Transformer show all
Defined in:
lib/ruby_transform/transformers/tapifier.rb

Overview

Method Temporary Variables to Tap Block

Looks for instances of method declarations where:

  1. A local variable is assigned to something as the first statement.

  2. As the last statement, that local variable is returned is expressed.

These instances of using “temporary variables” to construct something for returning can be more elegantly expressed by using the .tap idiom.

Example:

def my_method
  temp = ""
  temp << "Something"
  call_something(temp)
  temp
end

Converts To:

def my_method
  "".tap do |temp|
    temp << "Something"
    call_something(temp)
  end
end

Instance Method Summary collapse

Methods included from RubyTransform::TransformerHelpers

#sexp?

Instance Method Details

#expresses_local_variable?(e, local_variable) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/ruby_transform/transformers/tapifier.rb', line 56

def expresses_local_variable?(e, local_variable)
  (e.kind == :lvar && e.body[0] == local_variable) ||
  (e.kind == :return && expresses_local_variable?(e.body[0], local_variable))
end

#matches_block_to_use_tap?(e) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/ruby_transform/transformers/tapifier.rb', line 48

def matches_block_to_use_tap?(e)
  return matches_block_to_use_tap?(e.body[0]) if e.body.size == 1 && e.body[0].kind == :block
  
  e.is_a?(Sexp) && e.kind == :block &&   # Some block (or method body)
  e.body[0].kind == :lasgn &&  # The first line assigns to a local variable
  expresses_local_variable?(e.body[-1], e.body[0].body[0])
end

#matches_method_to_use_tap?(e) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/ruby_transform/transformers/tapifier.rb', line 43

def matches_method_to_use_tap?(e)
  e.is_a?(Sexp) && [:defn, :defs].include?(e.kind) && 
  matches_block_to_use_tap?(e.body[2])
end

#transform(e) ⇒ Object 



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# File 'lib/ruby_transform/transformers/tapifier.rb', line 31

def transform(e)
  super(transform_tapify_candidates(e))
end

#transform_block_to_use_tap(e) ⇒ Object 



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# File 'lib/ruby_transform/transformers/tapifier.rb', line 65

def transform_block_to_use_tap(e)
  return s(:scope, transform_block_to_use_tap(e.body[0])) if e.body.size == 1 && e.kind == :scope && e.body[0].kind == :block
  
  s(:block, s(:iter, 
    s(:call, e.body[0].body[1], :tap, s(:arglist)),
    s(:lasgn, e.body[0].body[0]),
    s(*([:block] + e.body[1..-2]))
  ))
end

#transform_method_to_use_tap(e) ⇒ Object 



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# File 'lib/ruby_transform/transformers/tapifier.rb', line 61

def transform_method_to_use_tap(e)
  s(e.kind, e.body[0], e.body[1], transform_block_to_use_tap(e.body[2]))
end

#transform_tapify_candidates(e) ⇒ Object 



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# File 'lib/ruby_transform/transformers/tapifier.rb', line 35

def transform_tapify_candidates(e)
  if matches_method_to_use_tap?(e)
    transform_method_to_use_tap(e)
  else
    e
  end
end