String-related helpers return undefined for empty strings

A number of string-related helpers return undefined when passed empty strings:

• capitalize
• capitalizeAll
• center
• ellipsis
• hyphenate
• isString
• lowercase
• pathcase
• plusify
• replace
• reverse
• sentence
• split
• titleize
• truncate
• uppercase

The library uses this expression to validate string arguments:

utils.isString = function(val) {
  return val && typeof val === 'string';
};

This returns false for empty strings even though they’re valid strings. Usually, this is not an issue in a Handlebars template as undefined renders empty but, might be a problem if one is calling any of these helpers from other helpers.

I do understand that this might be intentional to skip string manipulation for empty strings and, that existing code could rely on these behavior but, interestingly, rectifying the above expression does not break any of the 419 tests.

I would propose changing the code or, docs and tests to make this explicit.

[jonschlinkert]

Are we okay with documenting this?

Yes, that looks good to me, thanks.

they should all be consistent

agreed, I think we should go with the first option as well. thanks

[jonschlinkert]

I mentioned that this would break code in the linked pr. Just because tests aren’t breaking doesn’t mean that downstream implementations won’t break.

Any subexpressions using these helpers that check for either a string or undefined will break.

edit: try the following:

var handlebars = require('handlebars');

handlebars.registerHelper('foo', function() {
});

var fn = handlebars.compile('{{foo}}')
console.log(fn());

When the value returned by a helper is undefined, handlebars renders an empty string. Are you using the helpers as subexpressions, and checking for an empty string? If so, that’s the problem. I believe these helpers are returning the correct value.

Also, since you pointed out a few helpers that aren’t using isString, we should probably update those to use isString as well.