Null should yield empty string when resolving variable

[lukaszb]

This is related to #236. Am upvoting for showing empty string when resolving null object.

This is more similar to engines that swig is based on (Jinja/Django both resolves None as empty strings) and most of the time is more desired (I guess) than opaque [Object object].

While writing tests was pretty straightforward, have to admit I am not sure about the implementation.

Let me know what you think.

[tweakmds]

I just switched from 0.14.0 to 1.3.2, and noticed that all my empty values are now rendered as "undefined".
This is also contrary to the documentation, which lists "If a variable is not defined, don't worry, your template won't explode. Instead, an empty-string will be output in its place"

[mannyvergel]

Please show empty string when value is null. Currently it shows [Object object]

[paularmstrong]

My only hesitations with this is that it suppresses some potential conditionals that one might do (see examples below)... however, they don't work as one might expect...

This doesn't work because null in the template is not actually null in javascript.

{% if foo === null %} ... {% endif %}

The JS equivalent would be:

if (ctx.foo === ctx.null) { ... }

The same can be said for undefined.

However, apparently I've never needed to do any comparisons on null or undefined and no one has complained thus far. I think this is one of those exceptions that's probably okay for Swig's way of doing things is okay to be different than JS.

[lukaszb]

Agree on JS vs Swig way. Thanks for the merge!

[fundon]

@paularmstrong Please release a new version. Thanks!