Class: Rewrite::Prelude::Please

Inherits:
SexpProcessor
  • Object
show all
Defined in:
lib/rewrite/prelude/please.rb

Overview

Adds a polite method invocation to Ruby:

with(please) do
  ...
  @phone = Location.find(:first, ...elided... ).please.phone
  ...
end

Based on “try()”:ozmm.org/posts/try.html by Chris Wanstrath, but with method chaining syntax instead of with a send-like syntax.

It also works with parameters, blocks, and procs passed as blocks.

Works by rewriting expressions like:

numbers.please.inject(&:+)

Into:

lambda { |__1234567890__|
  if __1234567890__.respond_to? :inject
    __1234567890__.inject(&:+)
  end
}.call(numbers)

See also: Try, Andand

Instance Method Summary collapse

Instance Method Details

#process_block_pass(exp) ⇒ Object 



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# File 'lib/rewrite/prelude/please.rb', line 127

def process_block_pass(exp)
  orig = lambda { |exp_dup|
    lambda { Ruby2Ruby.new.process(exp_dup) }
  }.call(exp)
  # [:block_pass, [:lit, :+], [:call, [:call, [:vcall, :foo], :please], :bar]]
  # [:block_pass, [:lit, :blitz], [:call, [:call, [:vcall, :foo], :please], :bar, [:array, [:lit, :bash]]]]
  exp.shift
  # [[:lit, :+], [:call, [:call, [:vcall, :foo], :please], :bar]]
  # [[:lit, :blitz], [:call, [:call, [:vcall, :foo], :please], :bar, [:array, [:lit, :bash]]]]
  block_exp = process_inner_expr(exp.shift)
  call_exp = exp.shift
  raise "expected block_pass to have a receiver and a call form near #{orig.call}" unless exp.empty?
  # [:call, [:call, [:vcall, :foo], :please], :bar]
  # [:call, [:call, [:vcall, :foo], :please], :bar, [:array, [:lit, :bash]]]
  raise 'confused' unless call_exp.shift == :call
  # [[:call, [:vcall, :foo], :please], :bar]
  # [[:call, [:vcall, :foo], :please], :bar, [:array, [:lit, :bash]]]
  receiver_sexp = call_exp.first
  if matches_please_invocation(receiver_sexp) # [:call, [:vcall, :foo], :please]
    call_exp.shift
    # [:bar]
    # [:bar, [:array, [:lit, :bash]]]
    mono_parameter = Rewrite.gensym()
    s(:call, 
      s(:iter, 
        s(:fcall, :lambda), 
        s(:dasgn_curr, mono_parameter), 
        s(:if, 
          s(:call, s(:dvar, mono_parameter), :respond_to?, s(:array, s(:lit, receiver_sexp[2]))),
          s(:block_pass,
            block_exp,
            s(:call, 
              s(:dvar, mono_parameter), 
              *(call_exp.map { |inner| process_inner_expr inner })
            )
          ), 
          s(:nil)
        )
      ), 
      :call, 
      s(:array, 
        process_inner_expr(receiver_sexp[1]) # s(:lit, :foo)
      )
    )
  else
    s(:block_pass,
      block_exp,
      s(:call,
        *(call_exp.map { |inner| process_inner_expr inner })
      )
    )
  end
end

#process_call(exp) ⇒ Object 



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# File 'lib/rewrite/prelude/please.rb', line 84

def process_call(exp)
  # s(:call, s(:call, s(:lit, :foo), :please), :bar)
  exp.shift
  # s(s(:call, s(:lit, :foo), :please), :bar)
  receiver_sexp = exp.first
  if matches_please_invocation(receiver_sexp) # s(:call, s(:lit, :foo), :please)
    exp.shift
    # s( :bar )
    mono_parameter = Rewrite.gensym()
    s(:call, 
      s(:iter, 
        s(:fcall, :lambda), 
        s(:dasgn_curr, mono_parameter), 
        s(:if, 
          s(:call, s(:dvar, mono_parameter), :respond_to?, s(:array, s(:lit, receiver_sexp[2]))),
          begin
            s(:call, 
              s(:dvar, mono_parameter), 
              *(exp.map { |inner| process_inner_expr inner })
            )
          ensure
            exp.clear
          end,
          s(:nil)
        )
      ), 
      :call, 
      s(:array, 
        process_inner_expr(receiver_sexp[1]) # s(:lit, :foo)
      )
    )
  else
    # pass through
    begin
      s(:call,
        *(exp.map { |inner| process_inner_expr inner })
      )
    ensure
      exp.clear
    end
  end
end

#process_iter(exp) ⇒ Object 



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# File 'lib/rewrite/prelude/please.rb', line 41

def process_iter(exp)
  exp.shift
  receiver_sexp = exp.first #[:call, [:call, [:lit, 1..10], :please], :inject]
  if receiver_sexp[0] == :call && matches_please_invocation(receiver_sexp[1])
    exp.shift
    mono_parameter = Rewrite.gensym()
    s(:call, 
      s(:iter, 
        s(:fcall, :lambda), 
        s(:dasgn_curr, mono_parameter),
        #[:if, [:call, [:dvar, :mono], :respond_to?, [:array, [:lit, :foo]]], [:call, [:dvar, :mono], :foo], nil] 
        s(:if, 
          s(:call, s(:dvar, mono_parameter), :respond_to?, s(:array, s(:lit, receiver_sexp[2]))),
          begin
            s(:iter, 
              s(:call, 
                s(:dvar, mono_parameter), 
                *(receiver_sexp[2..-1].map { |inner| process_inner_expr inner })
              ), 
              *(exp.map { |inner| process_inner_expr inner })
            )
          ensure
            exp.clear
          end, 
          s(:nil)
        )
      ), 
      :call, 
      s(:array, 
        process_inner_expr(receiver_sexp[1][1]) # s(:lit, 1..10)
      )
    )
  else
    begin
      s(:iter,
        *(exp.map { |inner| process_inner_expr inner })
      )
    ensure
      exp.clear
    end
  end
end