Allow paths to start with ::

askama_shared/src/generator.rs

@@ -1342,10 +1342,15 @@ impl<'a, S: std::hash::BuildHasher> Generator<'a, S> {
     }
 
     fn visit_path(&mut self, buf: &mut Buffer, path: &[&str]) -> DisplayWrap {
-        for (i, part) in path.iter().enumerate() {
-            if i > 0 {
-                buf.write("::");
+        let mut it = path.iter();
+        match it.next() {
+            Some(&part) if part != "::" => {
+                buf.write(part);
             }
+            _ => {}
+        }
+        for part in it {
+            buf.write("::");
             buf.write(part);
         }
         DisplayWrap::Unwrapped
@@ -1357,10 +1362,15 @@ impl<'a, S: std::hash::BuildHasher> Generator<'a, S> {
         path: &[&str],
         args: &[Expr],
     ) -> Result<DisplayWrap, CompileError> {
-        for (i, part) in path.iter().enumerate() {
-            if i > 0 {
-                buf.write("::");
+        let mut it = path.iter();
+        match it.next() {
+            Some(&part) if part != "::" => {
+                buf.write(part);
             }
+            _ => {}
+        }
+        for part in it {
+            buf.write("::");
             buf.write(part);
         }
         buf.write("(");

askama_shared/src/parser.rs

@@ -1,7 +1,7 @@
 use nom::branch::alt;
 use nom::bytes::complete::{escaped, is_not, tag, take_until};
 use nom::character::complete::{anychar, char, digit1};
-use nom::combinator::{complete, map, opt};
+use nom::combinator::{complete, map, opt, value};
 use nom::error::ParseError;
 use nom::multi::{many0, many1, separated_list0, separated_list1};
 use nom::sequence::{delimited, pair, tuple};
@@ -312,10 +312,12 @@ fn expr_var_call(i: &[u8]) -> IResult<&[u8], Expr> {
 }
 
 fn path(i: &[u8]) -> IResult<&[u8], Vec<&str>> {
+    let root = opt(value("::", ws(tag("::"))));
     let tail = separated_list1(ws(tag("::")), identifier);
-    let (i, (start, _, rest)) = tuple((identifier, ws(tag("::")), tail))(i)?;
-
-    let mut path = vec![start];
+    let (i, (root, start, _, rest)) = tuple((root, identifier, ws(tag("::")), tail))(i)?;
+    let mut path = Vec::new();
+    path.extend(root);
+    path.push(start);
     path.extend(rest);
     Ok((i, path))
 }