Newlines and Temple

[Magnus Holm]

Okay, Temple does now support line-handling!

~> What's line-handling all about? Getting nicer error messages!

Let's say you have a Liquid-template called user.liquid:

Hello World!

{% if user.name == current_user.name %}

  {{ user.name | downcase }}

{% endif %}

If the downcase-filter raises an error, then the error should be reported as:

RuntimeError: OH NO!

from user.liquid:3

~> How?

I've introduced a new type: [:newline]. This basically means: "There was a newline here in the source, so there should also be a newline here in the generated code." Please note that this has *nothing* to do with newlines in the rendered string (that would simply be [:static, "\n"]).

To show you some examples:

[:multi,

  [:static, "Hello"],

  [:dynamic, "world"]]

Because there are no :newlines, this will be put on a single line:

_buf = [] ; _buf << "Hello" ; _buf << (world) ; _buf.join

[:multi,

  [:static, "Hello"],

  [:newline],

  [:dynamic, "world"]]

Here it's a method on line 2 (world), and because there is a :newline above it, it will stay on line 2:

_buf = [] ; _buf << "Hello" ; 

 ; _buf << (world) ; _buf.join

~> What about DynamicInliner?

DynamicInliner is a filter which compiles static and dynamic into a single dynamic string where the dynamic parts are added as interpolation:

[:multi,

  [:static, "Hello"],

  [:dynamic, "@world"],

  [:dynamic, "@yeah"],

  [:static, "Nice"]]

After running DynamicInliner, the generated code will be:

_buf = [] ; _buf << ("Hello#{@world}#{@yeah}Nice") ; _buf.join

We just saved 3 method calls and 3 strings which had to be garbage collected :-)

So how does this work with newlines? I think I've found a quite elegant solution:

_buf = [] ; _buf << ("Hello"\

"#{@world}#{@yeah}"\

"Nice") ; _buf.join

Because Ruby supports escaping of newlines and automatically concated strings (try this in IRB: "Hello " "World!"), it's syntactically equal to the previous code, but it's now spread across several lines. Victory!

// Magnus Holm