Macro.to_string/2 hard deprecated with no suitable replacement

[lukaszsamson]

Environment

• Elixir & Erlang/OTP versions (elixir --version):
  Erlang/OTP 24 [erts-12.1.2] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [jit]
  Elixir 1.13.0-rc.0 (48b838a) (compiled with Erlang/OTP 24)
• Operating system: macOS

Current behavior

Macro.to_string(expr, &modify_codegen/2)

warning: Macro.to_string/2 is deprecated. Use Macro.to_string/1 instead
  lib/erl2ex/pipeline/codegen.ex:505: Erl2ex.Pipeline.Codegen.expr_to_string/1

There is no suitable replacement (or the docs are missing) for code that used Macro.to_sting/2 with custom changes to code output. Clearly Macro.to_string/1 cannot be used instead.

Expected behavior

No deprecation or otherwise a suitable warning pointing to how a similar effect can be achieved with Inspect.Algebra.format and Code.quoted_to_algebra. An example in Code.quoted_to_algebra docs would also help.

[josevalim]

We have replaced it on ExDoc and Ecto. The approaches are usually by doing a pre-pass on the data or a post-pass on the output. From a quick look at erl2ex, you could do a prewalk that matches on {:?, metadata, Elixir} and return a new variable that will be printed as is. If that's not enough, then please expand and I will be glad to help find a solution. In the worst case scenario you can part the Macro.to_string functionality. :)

Thanks for the reports btw!

[lukaszsamson]

Yep, doing a prewalk is always an option.