Issue 23: Trying to iterate over a string with repeated section should throw an error (JavaScript version)
Status:  New
Owner: ----
Reported by b.l.st...@gmail.com, May 27, 2009
Given the following template fragment
{.section term}
  {.repeated section @}
    <li>{@}</li>
  {.or}
    <li>{@}</li>
  {.end}
{.end}

The following input works as expected:
{term: ['one', 'two', 'three'] }

The following input however does not:
{term: 'one'}

On Firefox the string is treated as an array and returns a list element for
each character. On Internet Explorer it throws an error. The expected
result would have been to call the {.or} section of the template and only
produce a single list element.
 
The problem occurs on line 276 of json-template.js (210 2009-04-30), where
the code assumes that if the object exists and has a length value greater
than zero it will repeat the section:
  if (items && items.length > 0) 

Changing this line to test for the presence of an array fixes the error and
produces the expected result. The resulting fix is as follows:

  if (items && Object.prototype.toString.apply(items) === '[object Array]'
&& items.length > 0)
May 27, 2009
Project Member #1 gtempacc...@yahoo.com
This is basically a case where the error handling could be stricter rather than
silently trying to iterate over a string.

The behavior you describe as expected isn't what's intended, see:
https://code.google.com/p/json-template/wiki/Reference

The .or section is only expanded if the section is empty or missing -- not if it has
an item which isn't a list.

So I think we should just raise EvaluationError in case the node for a repeated
section isn't a list.


May 28, 2009
#2 b.l.st...@gmail.com
Ah, I interpreted the reference document slightly different and assumed the .or
section to be also executed if the intended target (a list) was not there. Perhaps
that was just wishful thinking.

The use case for this is automatically generated JSON from an XML source. I often get
the following XML:
  <list>
    <item>one</item>
    <item>two</item>
  </list>

The generated JSON then becomes:
  {list: {item: ['one', 'two'] }}

Unfortunately, when the list has only one element, the resulting JSON is:
  {list: {item: 'one'}}

I don't have much control (or rather, I don't want to) over the way the JSON is
generated as it is done automatically by an XSLT stylesheet from an XML source. I was
hoping to catch this case in the template.
May 31, 2009
Project Member #3 gtempacc...@yahoo.com
I see.  Yeah it's unforunate that you have that type of output and don't have control
over it.

But there are a lot of issues you can get with arbitrary JSON, and the general
solution is to modify the data dictionary (automatically).  I just checked in a
Python example of this, in python/jsontemplate/datadict*.py.

It should be simple to do a similar thing from JavaScript for your case, although
possibly  issue 22  is relevant too.

Jul 9, 2009
Project Member #4 gtempacc...@yahoo.com
(No comment was entered for this change.)
Summary: Trying to iterate over a string with repeated section should throw an error (JavaScript version)
Jul 24, 2009
#5 mikkelg
b.l.stein, what did you end up doing? I have the same issue; my JSON is converted from XML, so sometimes a 
value is an array of strings, sometimes it is a string.

I was thinking about converting certain strings to an array of a string (a singleton) manually, but it's not the 
nicest solution ...
Jul 27, 2009
#6 b.l.st...@gmail.com
I ended up writing formatter functions for some of my problem cases and rewriting the
JSON in other cases (with a simple recursive function.)
Nov 7, 2009
Project Member #7 gtempacc...@yahoo.com
(No comment was entered for this change.)
Labels: Todo-JS