Handlebars now supports subexpressions.
{{foo (bar 3)}}
Subexpressions are always evaluated as helpers; if
`3` were omitted from the above example, `bar`
would be invoked as a param-less helper, even
though a top-levell `{{bar}}` would be considered
ambiguous.
The return value of a subexpression helper is
passed in as a parameter of a parent subexpression
helper, even in string params mode. Their type,
as listed in `options.types` or `options.hashTypes`
in string params mode, is "sexpr".
The main conceptual change in the Handlebars code
is that there is a new AST.SexprNode that manages
the params/hash passed into a mustache, as well
as the logic that governs whether that mustache
is a helper invocation, property lookup, etc.
MustacheNode, which used to manage this stuff,
still exists, but only manages things like
white-space stripping and whether the mustache
is escaped or not. So, a MustacheNode _has_
a SexprNode.
The introduction of subexpressions is fully
backwards compatible, but a few things needed
to change about the compiled output of a template
in order to support subexpressions. The main one
is that the options hash is no longer stashed in
a local `options` var before being passed to
either the helper being invoked or the
`helperMissing` fallback. Rather, the options
object is inlined in these cases. This does
mean compiled template sizes will be a little
bit larger, even those that don't make use of
subexpressions, but shouldn't have any noticeable
impact on performance when actually rendering
templates as only one of these inlined objects
will actually get evaluated.
Escaped-escape mustaches ("\\{{") immediately following escaped
mustaches ("\{{") were being handled incorrectly.
Fix the lookahead to make sure yytext still contains the appropriate
slashes when we pop out of <emu> so they can be handled consistently
by the initial state.
The idea is that the environment wraps up the mutable stuff in
Handlebars (like the helpers) and that you could theoretically create a
new one at any time and pass it in to Handlebars.template.
Every test makes a new environment and uses it in template compilation.
kpdecker
machty
Blake Embrey
Stanley Stuart
Daniel Marcotte
denniskuczynski
Laurie Harper
Yehuda Katz