Unify handling of calls (#614)

Instead of having `Expr::VarCall`, `Expr::PathCall` and
`Expr::MethodCall`, this PR unifies the handling of calls by removing
the former three variants, and introducing `Expr::Call`.

3 files changed, 239 insertions, 145 deletions

diff --git a/askama_shared/src/generator.rs b/askama_shared/src/generator.rs
index 53729c6..fabe277 100644
--- a/askama_shared/src/generator.rs
+++ b/askama_shared/src/generator.rs
@@ -603,7 +603,7 @@ impl<'a, S: std::hash::BuildHasher> Generator<'a, S> {
             // If `iter` is a call then we assume it's something that returns
             // an iterator. If not then the user can explicitly add the needed
             // call without issues.
-            Expr::MethodCall(..) | Expr::PathCall(..) | Expr::Index(..) => {
+            Expr::Call(..) | Expr::Index(..) => {
                 buf.writeln(&format!("let _iter = ({}).into_iter();", expr_code))
             }
             // If accessing `self` then it most likely needs to be
@@ -1049,9 +1049,7 @@ impl<'a, S: std::hash::BuildHasher> Generator<'a, S> {
             Expr::StrLit(s) => self.visit_str_lit(buf, s),
             Expr::CharLit(s) => self.visit_char_lit(buf, s),
             Expr::Var(s) => self.visit_var(buf, s),
-            Expr::VarCall(var, ref args) => self.visit_var_call(buf, var, args)?,
             Expr::Path(ref path) => self.visit_path(buf, path),
-            Expr::PathCall(ref path, ref args) => self.visit_path_call(buf, path, args)?,
             Expr::Array(ref elements) => self.visit_array(buf, elements)?,
             Expr::Attr(ref obj, name) => self.visit_attr(buf, obj, name)?,
             Expr::Index(ref obj, ref key) => self.visit_index(buf, obj, key)?,
@@ -1060,9 +1058,7 @@ impl<'a, S: std::hash::BuildHasher> Generator<'a, S> {
             Expr::BinOp(op, ref left, ref right) => self.visit_binop(buf, op, left, right)?,
             Expr::Range(op, ref left, ref right) => self.visit_range(buf, op, left, right)?,
             Expr::Group(ref inner) => self.visit_group(buf, inner)?,
-            Expr::MethodCall(ref obj, method, ref args) => {
-                self.visit_method_call(buf, obj, method, args)?
-            }
+            Expr::Call(ref obj, ref args) => self.visit_call(buf, obj, args)?,
             Expr::RustMacro(name, args) => self.visit_rust_macro(buf, name, args),
         })
     }
@@ -1234,20 +1230,15 @@ impl<'a, S: std::hash::BuildHasher> Generator<'a, S> {
                 buf.write("&(");
             }
 
-            let scoped = matches!(
-                arg,
-                Expr::Filter(_, _)
-                    | Expr::MethodCall(_, _, _)
-                    | Expr::VarCall(_, _)
-                    | Expr::PathCall(_, _)
-            );
-
-            if scoped {
-                buf.writeln("{")?;
-                self.visit_expr(buf, arg)?;
-                buf.writeln("}")?;
-            } else {
-                self.visit_expr(buf, arg)?;
+            match arg {
+                Expr::Call(left, _) if !matches!(left.as_ref(), Expr::Path(_)) => {
+                    buf.writeln("{")?;
+                    self.visit_expr(buf, arg)?;
+                    buf.writeln("}")?;
+                }
+                _ => {
+                    self.visit_expr(buf, arg)?;
+                }
             }
 
             if borrow {
@@ -1283,7 +1274,7 @@ impl<'a, S: std::hash::BuildHasher> Generator<'a, S> {
             }
         }
         self.visit_expr(buf, obj)?;
-        buf.write(&format!(".{}", attr));
+        buf.write(&format!(".{}", normalize_identifier(attr)));
         Ok(DisplayWrap::Unwrapped)
     }
 
@@ -1301,15 +1292,14 @@ impl<'a, S: std::hash::BuildHasher> Generator<'a, S> {
         Ok(DisplayWrap::Unwrapped)
     }
 
-    fn visit_method_call(
+    fn visit_call(
         &mut self,
         buf: &mut Buffer,
-        obj: &Expr<'_>,
-        method: &str,
+        left: &Expr<'_>,
         args: &[Expr<'_>],
     ) -> Result<DisplayWrap, CompileError> {
-        if matches!(obj, Expr::Var("loop")) {
-            match method {
+        match left {
+            Expr::Attr(left, method) if **left == Expr::Var("loop") => match *method {
                 "cycle" => match args {
                     [arg] => {
                         if matches!(arg, Expr::Array(arr) if arr.is_empty()) {
@@ -1329,16 +1319,22 @@ impl<'a, S: std::hash::BuildHasher> Generator<'a, S> {
                     _ => return Err("loop.cycle(…) expects exactly one argument".into()),
                 },
                 s => return Err(format!("unknown loop method: {:?}", s).into()),
+            },
+            left => {
+                match left {
+                    Expr::Var(name) => match self.locals.resolve(name) {
+                        Some(resolved) => buf.write(&resolved),
+                        None => buf.write(&format!("(&self.{})", normalize_identifier(name))),
+                    },
+                    left => {
+                        self.visit_expr(buf, left)?;
+                    }
+                }
+
+                buf.write("(");
+                self._visit_args(buf, args)?;
+                buf.write(")");
             }
-        } else {
-            if let Expr::Var("self") = obj {
-                buf.write("self");
-            } else {
-                self.visit_expr(buf, obj)?;
-            }
-            buf.write(&format!(".{}(", normalize_identifier(method)));
-            self._visit_args(buf, args)?;
-            buf.write(")");
         }
         Ok(DisplayWrap::Unwrapped)
     }
@@ -1421,24 +1417,6 @@ impl<'a, S: std::hash::BuildHasher> Generator<'a, S> {
         DisplayWrap::Unwrapped
     }
 
-    fn visit_path_call(
-        &mut self,
-        buf: &mut Buffer,
-        path: &[&str],
-        args: &[Expr<'_>],
-    ) -> Result<DisplayWrap, CompileError> {
-        for (i, part) in path.iter().enumerate() {
-            if i > 0 {
-                buf.write("::");
-            }
-            buf.write(part);
-        }
-        buf.write("(");
-        self._visit_args(buf, args)?;
-        buf.write(")");
-        Ok(DisplayWrap::Unwrapped)
-    }
-
     fn visit_var(&mut self, buf: &mut Buffer, s: &str) -> DisplayWrap {
         if s == "self" {
             buf.write(s);
@@ -1449,24 +1427,6 @@ impl<'a, S: std::hash::BuildHasher> Generator<'a, S> {
         DisplayWrap::Unwrapped
     }
 
-    fn visit_var_call(
-        &mut self,
-        buf: &mut Buffer,
-        s: &str,
-        args: &[Expr<'_>],
-    ) -> Result<DisplayWrap, CompileError> {
-        buf.write("(");
-        let s = normalize_identifier(s);
-        if !self.locals.contains(&s) && s != "self" {
-            buf.write("self.");
-        }
-        buf.write(s);
-        buf.write(")(");
-        self._visit_args(buf, args)?;
-        buf.write(")");
-        Ok(DisplayWrap::Unwrapped)
-    }
-
     fn visit_bool_lit(&mut self, buf: &mut Buffer, s: &str) -> DisplayWrap {
         buf.write(s);
         DisplayWrap::Unwrapped
@@ -1693,14 +1653,6 @@ where
         }
     }
 
-    fn contains(&self, key: &K) -> bool {
-        self.scopes.iter().rev().any(|set| set.contains_key(key))
-            || match self.parent {
-                Some(set) => set.contains(key),
-                None => false,
-            }
-    }
-
     /// Iterates the scopes in reverse and returns `Some(LocalMeta)`
     /// from the first scope where `key` exists.
     fn get(&self, key: &K) -> Option<&V> {
diff --git a/askama_shared/src/parser.rs b/askama_shared/src/parser.rs
index f5685b9..f429628 100644
--- a/askama_shared/src/parser.rs
+++ b/askama_shared/src/parser.rs
@@ -52,9 +52,7 @@ pub enum Expr<'a> {
     StrLit(&'a str),
     CharLit(&'a str),
     Var(&'a str),
-    VarCall(&'a str, Vec<Expr<'a>>),
     Path(Vec<&'a str>),
-    PathCall(Vec<&'a str>, Vec<Expr<'a>>),
     Array(Vec<Expr<'a>>),
     Attr(Box<Expr<'a>>, &'a str),
     Index(Box<Expr<'a>>, Box<Expr<'a>>),
@@ -63,7 +61,7 @@ pub enum Expr<'a> {
     BinOp(&'a str, Box<Expr<'a>>, Box<Expr<'a>>),
     Range(&'a str, Option<Box<Expr<'a>>>, Option<Box<Expr<'a>>>),
     Group(Box<Expr<'a>>),
-    MethodCall(Box<Expr<'a>>, &'a str, Vec<Expr<'a>>),
+    Call(Box<Expr<'a>>, Vec<Expr<'a>>),
     RustMacro(&'a str, &'a str),
 }
 
@@ -86,7 +84,7 @@ impl Expr<'_> {
             // The result of a call likely doesn't need to be borrowed,
             // as in that case the call is more likely to return a
             // reference in the first place then.
-            VarCall(..) | Path(..) | PathCall(..) | MethodCall(..) => true,
+            Call(..) | Path(..) => true,
             // If the `expr` is within a `Unary` or `BinOp` then
             // an assumption can be made that the operand is copy.
             // If not, then the value is moved and adding `.clone()`
@@ -296,11 +294,6 @@ fn expr_var(i: &str) -> IResult<&str, Expr<'_>> {
     map(identifier, Expr::Var)(i)
 }
 
-fn expr_var_call(i: &str) -> IResult<&str, Expr<'_>> {
-    let (i, (s, args)) = tuple((ws(identifier), arguments))(i)?;
-    Ok((i, Expr::VarCall(s, args)))
-}
-
 fn path(i: &str) -> IResult<&str, Vec<&str>> {
     let root = opt(value("", ws(tag("::"))));
     let tail = separated_list1(ws(tag("::")), identifier);
@@ -335,11 +328,6 @@ fn expr_path(i: &str) -> IResult<&str, Expr<'_>> {
     Ok((i, Expr::Path(path)))
 }
 
-fn expr_path_call(i: &str) -> IResult<&str, Expr<'_>> {
-    let (i, (path, args)) = tuple((ws(path), arguments))(i)?;
-    Ok((i, Expr::PathCall(path, args)))
-}
-
 fn named_target(i: &str) -> IResult<&str, (&str, Target<'_>)> {
     let (i, (src, target)) = pair(identifier, opt(preceded(ws(char(':')), target)))(i)?;
     Ok((i, (src, target.unwrap_or(Target::Name(src)))))
@@ -510,52 +498,39 @@ fn expr_single(i: &str) -> IResult<&str, Expr<'_>> {
         expr_num_lit,
         expr_str_lit,
         expr_char_lit,
-        expr_path_call,
         expr_path,
         expr_rust_macro,
         expr_array_lit,
-        expr_var_call,
         expr_var,
         expr_group,
     ))(i)
 }
 
-fn attr(i: &str) -> IResult<&str, (&str, Option<Vec<Expr<'_>>>)> {
-    let (i, (_, attr, args)) = tuple((
-        ws(char('.')),
-        alt((num_lit, identifier)),
-        ws(opt(arguments)),
-    ))(i)?;
-    Ok((i, (attr, args)))
+enum Suffix<'a> {
+    Attr(&'a str),
+    Index(Expr<'a>),
+    Call(Vec<Expr<'a>>),
 }
 
-fn expr_attr(i: &str) -> IResult<&str, Expr<'_>> {
-    let (i, (obj, attrs)) = tuple((expr_single, many0(attr)))(i)?;
-
-    let mut res = obj;
-    for (aname, args) in attrs {
-        res = if let Some(args) = args {
-            Expr::MethodCall(Box::new(res), aname, args)
-        } else {
-            Expr::Attr(Box::new(res), aname)
-        };
-    }
-
-    Ok((i, res))
+fn expr_attr(i: &str) -> IResult<&str, Suffix<'_>> {
+    map(
+        preceded(
+            ws(pair(char('.'), not(char('.')))),
+            cut(alt((num_lit, identifier))),
+        ),
+        Suffix::Attr,
+    )(i)
 }
 
-fn expr_index(i: &str) -> IResult<&str, Expr<'_>> {
-    let key = opt(tuple((ws(char('[')), expr_any, ws(char(']')))));
-    let (i, (obj, key)) = tuple((expr_attr, key))(i)?;
-    let key = key.map(|(_, key, _)| key);
+fn expr_index(i: &str) -> IResult<&str, Suffix<'_>> {
+    map(
+        preceded(ws(char('[')), cut(terminated(expr_any, ws(char(']'))))),
+        Suffix::Index,
+    )(i)
+}
 
-    Ok((
-        i,
-        match key {
-            Some(key) => Expr::Index(Box::new(obj), Box::new(key)),
-            None => obj,
-        },
-    ))
+fn expr_call(i: &str) -> IResult<&str, Suffix<'_>> {
+    map(arguments, Suffix::Call)(i)
 }
 
 fn filter(i: &str) -> IResult<&str, (&str, Option<Vec<Expr<'_>>>)> {
@@ -564,7 +539,7 @@ fn filter(i: &str) -> IResult<&str, (&str, Option<Vec<Expr<'_>>>)> {
 }
 
 fn expr_filtered(i: &str) -> IResult<&str, Expr<'_>> {
-    let (i, (obj, filters)) = tuple((expr_unary, many0(filter)))(i)?;
+    let (i, (obj, filters)) = tuple((expr_prefix, many0(filter)))(i)?;
 
     let mut res = obj;
     for (fname, args) in filters {
@@ -581,15 +556,27 @@ fn expr_filtered(i: &str) -> IResult<&str, Expr<'_>> {
     Ok((i, res))
 }
 
-fn expr_unary(i: &str) -> IResult<&str, Expr<'_>> {
-    let (i, (op, expr)) = tuple((opt(alt((ws(tag("!")), ws(tag("-"))))), expr_index))(i)?;
-    Ok((
-        i,
-        match op {
-            Some(op) => Expr::Unary(op, Box::new(expr)),
-            None => expr,
-        },
-    ))
+fn expr_prefix(i: &str) -> IResult<&str, Expr<'_>> {
+    let (i, (ops, mut expr)) = pair(many0(ws(alt((tag("!"), tag("-"))))), expr_suffix)(i)?;
+    for op in ops.iter().rev() {
+        expr = Expr::Unary(op, Box::new(expr));
+    }
+    Ok((i, expr))
+}
+
+fn expr_suffix(i: &str) -> IResult<&str, Expr<'_>> {
+    let (mut i, mut expr) = expr_single(i)?;
+    loop {
+        let (j, suffix) = opt(alt((expr_attr, expr_index, expr_call)))(i)?;
+        i = j;
+        match suffix {
+            Some(Suffix::Attr(attr)) => expr = Expr::Attr(expr.into(), attr),
+            Some(Suffix::Index(index)) => expr = Expr::Index(expr.into(), index.into()),
+            Some(Suffix::Call(args)) => expr = Expr::Call(expr.into(), args),
+            None => break,
+        }
+    }
+    Ok((i, expr))
 }
 
 fn expr_rust_macro(i: &str) -> IResult<&str, Expr<'_>> {
@@ -1348,7 +1335,10 @@ mod tests {
             super::parse("{{ Some(123) }}", &s).unwrap(),
             vec![Node::Expr(
                 Ws(false, false),
-                Expr::PathCall(vec!["Some"], vec![Expr::NumLit("123")],),
+                Expr::Call(
+                    Box::new(Expr::Path(vec!["Some"])),
+                    vec![Expr::NumLit("123")]
+                ),
             )],
         );
 
@@ -1356,14 +1346,14 @@ mod tests {
             super::parse("{{ Ok(123) }}", &s).unwrap(),
             vec![Node::Expr(
                 Ws(false, false),
-                Expr::PathCall(vec!["Ok"], vec![Expr::NumLit("123")],),
+                Expr::Call(Box::new(Expr::Path(vec!["Ok"])), vec![Expr::NumLit("123")]),
             )],
         );
         assert_eq!(
             super::parse("{{ Err(123) }}", &s).unwrap(),
             vec![Node::Expr(
                 Ws(false, false),
-                Expr::PathCall(vec!["Err"], vec![Expr::NumLit("123")],),
+                Expr::Call(Box::new(Expr::Path(vec!["Err"])), vec![Expr::NumLit("123")]),
             )],
         );
     }
@@ -1374,7 +1364,10 @@ mod tests {
             super::parse("{{ function(\"123\", 3) }}", &Syntax::default()).unwrap(),
             vec![Node::Expr(
                 Ws(false, false),
-                Expr::VarCall("function", vec![Expr::StrLit("123"), Expr::NumLit("3")]),
+                Expr::Call(
+                    Box::new(Expr::Var("function")),
+                    vec![Expr::StrLit("123"), Expr::NumLit("3")]
+                ),
             )],
         );
     }
@@ -1394,7 +1387,10 @@ mod tests {
             super::parse("{{ Option::Some(123) }}", &s).unwrap(),
             vec![Node::Expr(
                 Ws(false, false),
-                Expr::PathCall(vec!["Option", "Some"], vec![Expr::NumLit("123")],),
+                Expr::Call(
+                    Box::new(Expr::Path(vec!["Option", "Some"])),
+                    vec![Expr::NumLit("123")],
+                ),
             )],
         );
 
@@ -1402,8 +1398,8 @@ mod tests {
             super::parse("{{ self::function(\"123\", 3) }}", &s).unwrap(),
             vec![Node::Expr(
                 Ws(false, false),
-                Expr::PathCall(
-                    vec!["self", "function"],
+                Expr::Call(
+                    Box::new(Expr::Path(vec!["self", "function"])),
                     vec![Expr::StrLit("123"), Expr::NumLit("3")],
                 ),
             )],
@@ -1417,14 +1413,20 @@ mod tests {
             super::parse("{{ std::string::String::new() }}", &syntax).unwrap(),
             vec![Node::Expr(
                 Ws(false, false),
-                Expr::PathCall(vec!["std", "string", "String", "new"], vec![]),
+                Expr::Call(
+                    Box::new(Expr::Path(vec!["std", "string", "String", "new"])),
+                    vec![]
+                ),
             )],
         );
         assert_eq!(
             super::parse("{{ ::std::string::String::new() }}", &syntax).unwrap(),
             vec![Node::Expr(
                 Ws(false, false),
-                Expr::PathCall(vec!["", "std", "string", "String", "new"], vec![]),
+                Expr::Call(
+                    Box::new(Expr::Path(vec!["", "std", "string", "String", "new"])),
+                    vec![]
+                ),
             )],
         );
     }
@@ -1587,6 +1589,64 @@ mod tests {
     }
 
     #[test]
+    fn test_odd_calls() {
+        use Expr::*;
+        let syntax = Syntax::default();
+        assert_eq!(
+            super::parse("{{ a[b](c) }}", &syntax).unwrap(),
+            vec![Node::Expr(
+                Ws(false, false),
+                Call(
+                    Box::new(Index(Box::new(Var("a")), Box::new(Var("b")))),
+                    vec![Var("c")],
+                ),
+            )],
+        );
+        assert_eq!(
+            super::parse("{{ (a + b)(c) }}", &syntax).unwrap(),
+            vec![Node::Expr(
+                Ws(false, false),
+                Call(
+                    Box::new(Group(Box::new(BinOp(
+                        "+",
+                        Box::new(Var("a")),
+                        Box::new(Var("b"))
+                    )))),
+                    vec![Var("c")],
+                ),
+            )],
+        );
+        assert_eq!(
+            super::parse("{{ a + b(c) }}", &syntax).unwrap(),
+            vec![Node::Expr(
+                Ws(false, false),
+                BinOp(
+                    "+",
+                    Box::new(Var("a")),
+                    Box::new(Call(Box::new(Var("b")), vec![Var("c")])),
+                ),
+            )],
+        );
+        assert_eq!(
+            super::parse("{{ (-a)(b) }}", &syntax).unwrap(),
+            vec![Node::Expr(
+                Ws(false, false),
+                Call(
+                    Box::new(Group(Box::new(Unary("-", Box::new(Var("a")))))),
+                    vec![Var("b")],
+                ),
+            )],
+        );
+        assert_eq!(
+            super::parse("{{ -a(b) }}", &syntax).unwrap(),
+            vec![Node::Expr(
+                Ws(false, false),
+                Unary("-", Box::new(Call(Box::new(Var("a")), vec![Var("b")])),),
+            )],
+        );
+    }
+
+    #[test]
     fn test_parse_comments() {
         let s = &Syntax::default();
 
diff --git a/testing/tests/calls.rs b/testing/tests/calls.rs
new file mode 100644
index 0000000..052f34f
--- /dev/null
+++ b/testing/tests/calls.rs
@@ -0,0 +1,82 @@
+use askama::Template;
+
+#[derive(Template)]
+#[template(source = "{{ func(value) }}", ext = "txt")]
+struct OneFunction {
+    func: fn(&i32) -> i32,
+    value: i32,
+}
+
+#[test]
+fn test_one_func() {
+    let t = OneFunction {
+        func: |&i| 2 * i,
+        value: 123,
+    };
+    assert_eq!(t.render().unwrap(), "246");
+}
+
+#[derive(Template)]
+#[template(source = "{{ self.func(value) }}", ext = "txt")]
+struct OneFunctionSelf {
+    value: i32,
+}
+
+impl OneFunctionSelf {
+    fn func(&self, i: &i32) -> i32 {
+        2 * i
+    }
+}
+
+#[test]
+fn test_one_func_self() {
+    let t = OneFunctionSelf { value: 123 };
+    assert_eq!(t.render().unwrap(), "246");
+}
+
+#[derive(Template)]
+#[template(source = "{{ func[index](value) }}", ext = "txt")]
+struct OneFunctionIndex<'a> {
+    func: &'a [fn(&i32) -> i32],
+    value: i32,
+    index: usize,
+}
+
+#[test]
+fn test_one_func_index() {
+    let t = OneFunctionIndex {
+        func: &[|_| panic!(), |&i| 2 * i, |_| panic!(), |_| panic!()],
+        value: 123,
+        index: 1,
+    };
+    assert_eq!(t.render().unwrap(), "246");
+}
+
+struct AddToGetAFunction;
+
+impl std::ops::Add<usize> for &AddToGetAFunction {
+    type Output = fn(&i32) -> i32;
+
+    fn add(self, rhs: usize) -> Self::Output {
+        assert_eq!(rhs, 1);
+        |&i| 2 * i
+    }
+}
+
+#[derive(Template)]
+#[template(source = "{{ (func + index)(value) }}", ext = "txt")]
+struct OneFunctionBinop<'a> {
+    func: &'a AddToGetAFunction,
+    value: i32,
+    index: usize,
+}
+
+#[test]
+fn test_one_func_binop() {
+    let t = OneFunctionBinop {
+        func: &AddToGetAFunction,
+        value: 123,
+        index: 1,
+    };
+    assert_eq!(t.render().unwrap(), "246");
+}