quote |> Macro.to_string |> Code.string_to_quoted! injects indentation spacing in final quote string

[jiegillet]

Environment

• Elixir & Erlang/OTP versions (elixir --version):

Erlang/OTP 24 [erts-12.0.1] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1] [jit] [dtrace]

Elixir 1.12.0 (compiled with Erlang/OTP 23)

• Operating system: macOS 11.4

Current behavior

I tried quoting the following function, making it into a string and back into a quote:

def hi(name) do
  "hello\n#{name}" 
end

Currently:

iex(92)> quote do
...(92)>   def hi(name) do
...(92)>     "hello\n#{name}"
...(92)>   end
...(92)> end
{:def, [context: Elixir, import: Kernel],
 [
   {:hi, [context: Elixir], [{:name, [], Elixir}]},
   [
     do: {:<<>>, [],
      [
        "hello\n",       # Note the newline here...
        {:"::", [],
         [
           {{:., [], [Kernel, :to_string]}, [], [{:name, [], Elixir}]},
           {:binary, [], Elixir}
         ]}
      ]}
   ]
 ]}
iex(93)> |> Macro.to_string
"def(hi(name)) do\n  \"hello\n  \#{name}\"\nend"
iex(94)> |> tap(&IO.puts/1)
def(hi(name)) do
  "hello
  #{name}"       # ...is interpreted as an actual newline instead of being escaped...
end
"def(hi(name)) do\n  \"hello\n  \#{name}\"\nend"
iex(95)> |> Code.string_to_quoted!
{:def, [line: 1],
 [
   {:hi, [line: 1], [{:name, [line: 1], nil}]},
   [
     do: {:<<>>, [line: 2],
      [
        "hello\n  ",       # ...and the indentation after the newline is injected into the string
        {:"::", [line: 3],
         [
           {{:., [line: 3], [Kernel, :to_string]}, [line: 3],
            [{:name, [line: 3], nil}]},
           {:binary, [line: 3], nil}
         ]}
      ]}
   ]
 ]}

Expected behavior

I expected iex(95) to be identical to iex(92).

The string interpolation seems necessary to trigger the current behavior.
When I escape the newline as in "hello\\n#{name}", I get the expected behavior, but I can't escape the \n when using a multiline string.

[josevalim]

This has been fixed in Elixir master since Macro.to_string has been rewritten to use the same code path as the code formatter. Thank you!