Add support for partials and path segments for Handlebars.

This introduces support for some missing features to the Handlebars lexer:
Partials and path segments. Partials mostly appeared to work before, but the
`>` in `{{> ... }}` would appear as a syntax error, as could other
components of the partial. This change introduces support for:

* Standard partials: `{{> partialName}}`
* Partials with parameters: `{{> partialName varname="value"}}`
* Ddynamic partials: `{{> (partialFunc)}}`
* Ddynamic partials with lookups: `{{> (lookup ../path "partialName")}}`
* Partial blocks: `{{> @partial-block}}`
* Inline partials: `{{#*inline}}..{{/inline}}`

It also introduces support for path segments, which can reference content in
the current context or in a parent context. For instance, `this.name`,
`this/name`, `./name`, `../name`, `this/name`, etc. These are all now tracked
as variables.

2 files changed, 52 insertions, 3 deletions

diff --git a/pygments/lexers/templates.py b/pygments/lexers/templates.py
index e6eeaa25..da54c336 100644
--- a/pygments/lexers/templates.py
+++ b/pygments/lexers/templates.py
@@ -1814,8 +1814,9 @@ class HandlebarsLexer(RegexLexer):
             (r'\}\}', Comment.Preproc, '#pop'),
 
             # Handlebars
-            (r'([#/]*)(each|if|unless|else|with|log|in)', bygroups(Keyword,
+            (r'([#/]*)(each|if|unless|else|with|log|in(line)?)', bygroups(Keyword,
              Keyword)),
+            (r'#\*inline', Keyword),
 
             # General {{#block}}
             (r'([#/])([\w-]+)', bygroups(Name.Function, Name.Function)),
@@ -1823,11 +1824,37 @@ class HandlebarsLexer(RegexLexer):
             # {{opt=something}}
             (r'([\w-]+)(=)', bygroups(Name.Attribute, Operator)),
 
+            # Partials {{> ...}}
+            (r'(>)(\s*)(@partial-block)', bygroups(Keyword, Text, Keyword)),
+            (r'(#?>)(\s*)([\w-]+)', bygroups(Keyword, Text, Name.Variable)),
+            (r'(>)(\s*)(\()', bygroups(Keyword, Text, Punctuation),
+             'dynamic-partial'),
+
+            include('generic'),
+        ],
+        'dynamic-partial': [
+            (r'\s+', Text),
+            (r'\)', Punctuation, '#pop'),
+
+            (r'(lookup)(\s+)(\.|this)(\s+)', bygroups(Keyword, Text,
+                                                      Name.Variable, Text)),
+            (r'(lookup)(\s+)([^\s]+)', bygroups(Keyword, Text,
+                                                using(this, state='variable'))),
+            (r'[\w-]+', Name.Function),
+
+            include('generic'),
+        ],
+        'variable': [
+            (r'[a-zA-Z][\w-]*', Name.Variable),
+            (r'\.[\w-]+', Name.Variable),
+            (r'(this\/|\.\/|(\.\.\/)+)[\w-]+', Name.Variable),
+        ],
+        'generic': [
+            include('variable'),
+
             # borrowed from DjangoLexer
             (r':?"(\\\\|\\"|[^"])*"', String.Double),
             (r":?'(\\\\|\\'|[^'])*'", String.Single),
-            (r'[a-zA-Z][\w-]*', Name.Variable),
-            (r'\.[\w-]+', Name.Variable),
             (r"[0-9](\.[0-9]*)?(eE[+-][0-9])?[flFLdD]?|"
              r"0[xX][0-9a-fA-F]+[Ll]?", Number),
         ]
diff --git a/tests/examplefiles/demo.hbs b/tests/examplefiles/demo.hbs
index 1b9ed5a7..ae80cc1b 100644
--- a/tests/examplefiles/demo.hbs
+++ b/tests/examplefiles/demo.hbs
@@ -10,3 +10,25 @@
 {{else}}
   <button {{action expand}}>Show More...</button>
 {{/if}}
+
+{{> myPartial}}
+{{> myPartial var="value" }}
+{{> myPartial var=../value}}
+{{> (myPartial)}}
+{{> (myPartial) var="value"}}
+{{> (lookup . "myPartial")}}
+{{> ( lookup . "myPartial" ) var="value" }}
+{{> (lookup ../foo "myPartial") var="value" }}
+{{> @partial-block}}
+
+{{#>myPartial}}
+...
+{{/myPartial}}
+
+{{#*inline "myPartial"}}
+...
+{{/inline}}
+
+{{../name}}
+{{./name}}
+{{this/name}}