Proposal: allow newline after `with`

[Po Chen]

x = %{x: 1}

with %{x: x} <- x do
  IO.inspect x
end

^ This works.

x = %{x: 1}

with
  %{x: x} <- x
do
  IO.inspect x
end

^ This is a syntax error.

Proposing that the latter should be allowed for 2 reasons:

1) it looks like it should work ¯\_(ツ)_/¯

this sounds like trolling but is really not. the syntax that looks valid should be valid.

2) it is better, more consistent for indentation and code formatting.

with %{a: a} <-
       some_really_long_line_about_a,
     %{b: b} <-
       some_really_long_line_about_a
do
  ...
end

^ this is what it would look like when formatted with the current syntax rules

• note the indentation of line 2 is 7 spaces
• and line 3 is indented 5 spaces

if newline is allow after `with`

with
  %{a: a} <-
    some_really_long_line_about_a,
  %{b: b} <-
    some_really_long_line_about_a
do
  ...
end

^ it would look like that

• everything is indented consistently, 2 spaces and 4
• no need to waste extra horizontal space
• also makes it easier for text editors to auto indent without having trouble with abnormal indent sizes

[José Valim]

Imagine you have this code:

   foo = 1

   bar = 2

   foo bar do

     :ok

   end

Would you expect it to be equivalent to:

   foo = 1

   bar = 2

   foo

   bar do

     :ok

   end

It isn’t because “foo” in its own line is a valid expression. Replace “foo” by “with” and you can see why your proposed syntax doesn’t work.

If you want to write it as you proposed, you need to use parens:

   foo = 1

   bar = 2

   foo(

     bar

   ) do

     :ok

   end

--

José Valim

www.plataformatec.com.br

Founder and 

Director of R&D

[Po Chen]

Ah I thought `with` was part of the language, then I realized how small the language core is.

Now I wish the language is actually a little bigger :S mixed feelings.

Thanks for the reply!

[Ben Wilson]

This is achievable with `\` btw:

with \

  %{x: x} <- y
do
  x
end

[José Valim]

Good call Ben! The formatter will rewrite it though, while it does keep parens.

José Valim

www.plataformatec.com.br

Founder and 

Director of R&D

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[OvermindDL1]

I'm still quite curious why `with` is not entirely in the body like `cond` and `case` and so forth is (ditto with `for`), so it'd be:

```elixir

with do

  %{x: x} <- y

  x

end

```

It follows the pattern of cond and so forth, no weird comma's needed, no weird prefix `do:` or so forth, you only need to split on `<-`, etc....

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[José Valim]

In the with proposal we explain that "with" was meant to mirror for-comprehensions. It has been also discussed that nowhere in Elixir we traverse the body retrieving expressions and that's not a precedent we want to introduce in the core language itself.

José Valim

www.plataformatec.com.br

Founder and 

Director of R&D

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[Po Chen]

Hi Jose,

I just tried going with parens, the formatter does not seem to keep parens either in this case..

[José Valim]

Please open up a bug report!

José Valim

www.plataformatec.com.br

Founder and 

Director of R&D

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