Subexpressions don't work with context resolving

[JustBlackBird]

In the current implementation subexpressions do not work with context at all.

I've created several tests to illustrate the problem.

[fzerorubigd]

Its not like that, I think. For example in {{concat a (concat c b)}} with array('a' => 'A', 'b' => 'B', 'c' => 'C') context :

result of concat c b is CB , so the final concat is concat a CB and CB is not in context and so the result is null (for CB), the real result we get is only 'c' and its correct.

I change your tests, If you think this is wrong, please explain it with more example.

Thank you!

[JustBlackBird]

@fzerorubigd you are wrong with your changes. In all my cases concat helper returns strings, not variables names. And that is the main problem -- there is no way to tell subexpressions that you return just strings.

Here is the example:

{{concat (concat a "\"\'[]") b}}

"\"\'[]" is a correct string, but not a correct variable name. If I try to render the template above I get an InvalidArgumentException with "variable name is invalid" message.

Moreover, according to your changes concat helper tries to get variable from the context and if it is not found it uses just it's name. It is the same as render {{var}} to "var" string if the var variable is not found in the context.

[fzerorubigd]

We need a better argument parser and a simple way to detect variables from the "string" inside helpers. In current API, the helper must detect this, but the better way is to pass an Arguments class to helpers (with ability to transform into string for preventing BC break) And this need much more work.

[everplays]

Before going for parsing arguments and stuff like that, I think we can use a warpper class like safe string to make difference between variable names and static strings. On Aug 29, 2014 1:26 PM, "Fzerorubigd" notifications@github.com wrote:

We need a better argument parser and a simple way to detect variables from the "string" inside helpers. In current API, the helper must detect this, but the better way is to pass an Arguments class to helpers (with ability to transform into string for preventing BC break) And this need much more work.

— Reply to this email directly or view it on GitHub https://github.com/XaminProject/handlebars.php/pull/80#issuecomment-53852431 .

[JustBlackBird]

@fzerorubigd, I agree. I think the current problem is tightly related with #74. It seems that all arguments stuff must be done in Handlebars core, not in a helper.

As for subexpressions, they are useless without proper work with context resolving.

[JustBlackBird]

@everplays, we cannot return string wrapper from a helper. Here any wrapper will be converted to string, so the parent helper will know nothing about such wrappers.

[everplays]

That needs to be fixed as well. However, Regardless of #74, we need a way to know what the result of a subexpression would mean. Subexpression might return the text "a". When it is referring to the variable a and when it means the static string a? We can fix this (which fixes this issue as well) by having a wrapper for static string. On Aug 29, 2014 1:38 PM, "Dmitriy S. Simushev" notifications@github.com wrote:

@everplays https://github.com/everplays, we cannot return string wrapper from a helper. Here https://github.com/XaminProject/handlebars.php/blob/master/src/Handlebars/Template.php#L359 any wrapper will be converted to string, so the parent helper will know nothing about such wrappers.

— Reply to this email directly or view it on GitHub https://github.com/XaminProject/handlebars.php/pull/80#issuecomment-53853357 .

[fzerorubigd]

I don't know exactly, How handlebars.js handle this? for example in concat a b how we can detect if this is plain a or variable name a? or simple we could use concat "a" "b" and concat a b the first for string and other for variable?

[JustBlackBird]

Here is Handlebars.js specs for subexpressions: https://github.com/wycats/handlebars.js/blob/master/spec/subexpressions.js

As I can see arguments in subexpressions are the same as in normal helpers:

• "smth" and 'smth' are strings;
• all other things are variables.

[everplays]

https://github.com/wycats/handlebars.js/blob/f4b8c5260c203d6ab7631fa394696f5c7a442586/spec/subexpressions.js#L125 is what we need which, from my understanding, is what I have described.

@fzerorubigd, @JustBlackBird What do you think?

[JustBlackBird]

@everplays, as I can see helpers always return strings, not variables names.

@fzerorubigd I found one more problem with tests. Here the test helper does not resolve variable name, but it should to! The correct helper's body is:

return $context->get($arg) . 'Test.';

As the result the tests are false positive, because they describe incorrect behavior.

@everplays, @fzerorubigd May be I should create a separate issue for discussion?

[fzerorubigd]

@JustBlackBird yes. Please create a seperate issue for that one too. Thank you!