Misc: Prior art

a.k.a., “Why should I use Expug over other template engines?”

There’s calliope and slime that brings Haml and Slim to Elixir, respectively. Expug offers a bit more:

Pug/Jade syntax!

The Pug syntax is something I personally find more sensible than Slim, and less noisy than Haml.

# Expug
p.alert(align="center") Hello!

%p.alert{align: "center"} Hello!

# Slime
p.alert align="center" Hello!

Expug tries to infer what you mean based on balanced parentheses. In contrast, you’re forced to use "#{...}" in slime.

# Expug
script(src=static_path(@conn, "/js/app.js") type="text/javascript")
#          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

# Slime
script[src="#{static_path(@conn, "/js/app.js")}" type="text/javascript"]

Also notice that you’re forced to use [ in Slime if your attributes have ( in it. Expug doesn’t have this restriction.

# Slime
a[href="/link" onclick="alert('Are you sure?')"]

Slime has optional braces, which leads to a lot of confusion. In Expug, parentheses are required.

# Slime
strong This is bold text.
strong color="blue" This is also valid, but confusing.

# Expug
strong(color="blue") Easier and less confusing!

True multilines

Expug has a non-line-based tokenizer that can figure out multiline breaks.

# Expug
= render App.UserView,
  conn: @conn

  style="font-weight: bold"

Using brace-matching, Expug’s parser can reliably figure out what you mean.

# Expug

Correct line number errors

Errors in Expug will always map to the correct source line numbers.

CompileError in show.html.pug (line 2):
assign @xyz not available in eex template.