Macro.to_string and Code.string_to_quoted adding more \ escape characters

[polvalente]

Environment

• Elixir & Erlang/OTP versions (elixir --version): Elixir 1.11.2 (compiled with Erlang/OTP 23), Erlang 23.2.5
• Operating system: Ubuntu 20.04

Current behavior

It seems that Macro.to_string is applying some escapes where it shouldn't. Maybe this is intended behavior, but I wasn't expecting it.

iex> "~r/\\a/" |> Code.string_to_quoted!() |> Macro.to_string             
"~r/\\\\a/"
iex> "~r/\\a/" |> Code.string_to_quoted!() |> Macro.to_string == "~r/\\a/"
false

From what I gathered, it seems to be something specific to explicit sigils:

iex> "~s/\\a/" |> Code.string_to_quoted!() |> Macro.to_string
"~s/\\\\a/" # This has two \\ added and isn't equivalent to the original input
iex> ~s/"\\a"/ |> Code.string_to_quoted!() |> Macro.to_string   
"\"\\a\"" # This yields an equivalent string to the original input

Expected behavior

iex> "~s/\\a/" |> Code.string_to_quoted!() |> Macro.to_string
"~s/\\a/"

[polvalente]

After digging a little through Macro.to_string/1 tests, it seems that this is the expected behavior. I noticed that IO.puts does print the original string back. Is there a way to yield this conversion as a string instead of writing it to stdio?

[polvalente]

It seems that quoted |> Macro.to_string() |> String.replace(~r/\\\\/, "\\") is what I want. If this is the correct solution to my problem, please let me know (and we can close the issue)!