Proposal: allow to create custom markers in EEx Engines

[Grych]

Hi all,

While building my own EEx Engine I encountered an issue, which might be easily resolved, if EEx.Engine allow to use custom markers.

As it stands in the documentation of EEx.Engine behaviour:

The allowed markers so far are: "" and "=".

The EExEngine API is prepared for having custom markers, as handle_expr/3 receives the marker, but currently it receives only "=" or "". Trying to put own marker treats it as a part of the expression.

My proposition is to create a list of additional markers to use by a developer who writes own EEx Engine. For a begin, it could be:

• "|"
• "/"

(none of those markers should confuse the "" marker, as they should not appear at the beginning of any Elixr expression)

By default, those markers may behave as "=". But when you create your own EEx Engine, you would be able to override handle_expr/3 for those markers.

-----------

Rough example:

defmodule ExtendedEngine do

  use EEx.Engine

  def handle_expr(buffer, "/", expr) do

    super(buffer, "=", modified_expression(expr))

  end

  def handle_expr(buffer, mark, expr) do

    super(buffer, mark, expr)

  end

end

Current behaviour:

iex> EEx.eval_string "foo <%/ bar %>", [bar: "baz"], engine: ExtendedEngine

** (SyntaxError) nofile:1: syntax error before: '/'

             lib/eex/compiler.ex:36: EEx.Compiler.generate_buffer/4

             lib/eex.ex:196: EEx.eval_string/3

    (stdlib) erl_eval.erl:670: :erl_eval.do_apply/6

       (iex) lib/iex/evaluator.ex:182: IEx.Evaluator.handle_eval/6

       (iex) lib/iex/evaluator.ex:175: IEx.Evaluator.do_eval/4

Expected behaviour:

iex> EEx.eval_string "foo <%/ bar %>", [bar: "baz"], engine: ExtendedEngine
"foo BAZ"

[José Valim]

Yes, we can support more markers. The default behaviour though should be to raise (and not be equiavlent to "=").

PR please?

José Valim

www.plataformatec.com.br

Skype: jv.ptec

Founder and Director of R&D

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[Grych]

Hi José,

W dniu sobota, 1 lipca 2017 12:33:58 UTC+2 użytkownik José Valim napisał:

Yes, we can support more markers. The default behaviour though should be to raise (and not be equiavlent to "=").

Good point, thanks!

 

PR please?

Will do.

 

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