separate out the parser for key because partials don't use a full path, only a key

src/parser/parser.rs

@@ -91,6 +91,9 @@ enum TemplateElement<'a> {
     TETag(DustTag<'a>),
 }
 
+/// Any element significant to dust that isn't plain text
+///
+/// These elements are always wrapped in curly braces
 fn dust_tag(i: &str) -> IResult<&str, DustTag> {
     alt((
         map(special, DustTag::DTSpecial),
@@ -102,6 +105,7 @@ fn dust_tag(i: &str) -> IResult<&str, DustTag> {
     ))(i)
 }
 
+/// Special characters
 fn special(i: &str) -> IResult<&str, Special> {
     delimited(
         tag("{~"),
@@ -116,27 +120,29 @@ fn special(i: &str) -> IResult<&str, Special> {
     )(i)
 }
 
+/// Part of a dust template that does not get rendered
 fn comment(i: &str) -> IResult<&str, Comment> {
     map(delimited(tag("{!"), take_until("!}"), tag("!}")), |body| {
         Comment { value: body }
     })(i)
 }
 
-fn path(i: &str) -> IResult<&str, Path> {
+/// A single element of a path
-    map(
+fn key(i: &str) -> IResult<&str, &str> {
-        separated_list(
+    recognize(tuple((
-            tag("."),
+        one_of("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_$"),
-            recognize(tuple((
+        opt(is_a(
-                one_of("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_$"),
+            "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_$0123456789-",
-                opt(is_a(
+        )),
-                    "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_$0123456789-",
+    )))(i)
-                )),
-            ))),
-        ),
-        |body| Path { keys: body },
-    )(i)
 }
 
+/// A series of keys separated by '.' to reference a variable in the context
+fn path(i: &str) -> IResult<&str, Path> {
+    map(separated_list(tag("."), key), |body| Path { keys: body })(i)
+}
+
+/// Display a value from the context
 fn reference(i: &str) -> IResult<&str, Reference> {
     let (remaining, (p, filters)) = delimited(tag("{"), tuple((path, many0(filter))), tag("}"))(i)?;
     Ok((