Phoenix: Unwanted whitespace trimming in EEx templates

[sn3p]

This is a known issue (#3482) but it was closed some time ago.
We are experiencing similar issues which are blocking us from updating to Elixir v1.9.0 and up.

According to the Elixir v1.9.0 release notes:

1. Bug fixes
   [EEx] Consistently trim newlines when you have a single EEx expression per line on multiple lines

What bug does this actually fix?

Edit: https://github.com/elixir-lang/elixir/issues/8792 fixed via https://github.com/phoenixframework/phoenix/commit/04295d8eb19ff7c65bd9f2b8f836040bd925c897

For now I would recommend to either go with double spaces or an explicit  .

I would expect everything outside EEx expressions to output exactly the way I write it, only replacing the expressions itself. Writing   or additional newlines feels like a hack rather than a fix. Extra load and error prone because this is not how you would write HTML.

Does this make sense or am I missing a bigger picture here? Please help me understand 😆

If this continues to be an issue, we can make trim optional.

That would be awesome!! Would be happy to give this a go.

Example

<%= "Hello" %> <%= "World" %>

"Hello World" (expected)

<%= "Hello" %>
<%= "World" %>

"HelloWorld" (unexpected)

<%= "Hello" %>

<%= "World" %>

"Hello World" (expected)

[josevalim]

The second example is an EEx bug. The trimming should only trim space after newlines, leaving at least one new line. It will be fixed on Elixir master and v1.10.

[josevalim]

Fixed in Elixir master. It was bigger than I thought, so I won't backport it to v1.10. If you want to make it configurable in Phoenix, a PR is also welcome. Thank you!

[josevalim]

I have added the option to master and v1.4 too.

[sn3p]

I have added the option to master and v1.4 too.

Awesome thank you so much 🎉
Wanted to give this a go tomorrow but you're too fast ⚡️

[sn3p]

I was thinking, in Ruby ERB you can enable trim mode per line by adding a - when closing the expression:

<% # avoids line break after expression -%>

Would this be possible and a helpful addition in EEx?