View Source Makeup.Lexer.Postprocess (Makeup v1.1.2)

Often you'll want to run the token list through a postprocessing stage before running the formatter.

Most of what we can do in a post-processing stage can be done with more parsing rules, but doing it in a post-processing stage is often easier and faster. Never assume one of the options is faster than the other, always measure performance.

Summary

Functions

Takes a list of the format [{key1, [val11, val12, ...]}, {key2, [val22, ...]}] and returns a map of the form %{val11 => key1, val12 => key2, ..., val22 => key2, ...}.

Converts the value of a token into a binary.

Converts the values of the tokens in the list into binaries.

Functions

Takes a list of the format [{key1, [val11, val12, ...]}, {key2, [val22, ...]}] and returns a map of the form %{val11 => key1, val12 => key2, ..., val22 => key2, ...}.

The resulting map may be useful to highlight some tokens in a special way in a postprocessing step.

You can also use pattern matching instead of the inverted map, and it will probably be faster, but always benchmark the alternatives before committing to an implementation.

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token_value_to_binary(arg)

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Converts the value of a token into a binary.

Token values are usually iolists for performance reasons. The BEAM is actually quite fast at printing or concatenating iolists, and some of the basic combinators output iolists, so there is no need to convert the token values into binaries.

This function should only be used for tesring purposes, when you might want to compare the token list into a reference output.

Converting the tokens into binaries has two advantges:

  1. It's much easier to compare tokens by visual inspection when the value is a binary
  2. When testing, two iolists that print to the same binary should be considered equal.

This function hasn't been optimized for speed. Don't use in production code.

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token_values_to_binaries(tokens)

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Converts the values of the tokens in the list into binaries.

Token values are usually iolists for performance reasons. The BEAM is actually quite fast at printing or concatenating iolists, and some of the basic combinators output iolists, so there is no need to convert the token values into binaries.

This function should only be used for tesring purposes, when you might want to compare the token list into a reference output.

Converting the tokens into binaries has two advantges:

  1. It's much easier to compare tokens by visual inspection when the value is a binary
  2. When testing, two iolists that print to the same binary should be considered equal.

Example

defmodule MyTest do
  use ExUnit.Case
  alias Makeup.Lexers.ElixirLexer
  alias Makeup.Lexer.Postprocess

  test "binaries are much easier on the eyes" do
    naive_tokens = ElixirLexer(":atom")
    # Hard to inspect visually
    assert naive_tokens == [{:string_symbol, %{language: :elixir}, [":", "a", "tom"]}]
    better_tokens =
      text
      |> ElixirLexer.lex()
      |> Postprocess.token_values_to_binaries()
    # Easy to inspect visually
    assert better_tokens == [{:string_symbol, %{language: :elixir}, ":atom"}]
  end
end

Actually, you'll want to define some kind of helper to make it less verbose. For example:

defmodule MyTest do
  use ExUnit.Case
  alias Makeup.Lexers.ElixirLexer
  alias Makeup.Lexer.Postprocess

  def lex(text) do
    text
    |> ElixirLexer.lex(group_prefix: "group")
    |> Postprocess.token_values_to_binaries()
  end

  test "even better with our little helper" do
    assert lex(":atom") == [{:string_symbol, %{language: :elixir}, ":atom"}]
  end
end