Move parser into askama_shared

2 files changed, 1094 insertions, 0 deletions

diff --git a/askama_shared/src/lib.rs b/askama_shared/src/lib.rs
index 8a64c22..b2f1271 100644
--- a/askama_shared/src/lib.rs
+++ b/askama_shared/src/lib.rs
@@ -16,6 +16,7 @@ mod error;
 pub use crate::error::{Error, Result};
 pub mod filters;
 pub mod helpers;
+pub mod parser;
 
 #[derive(Debug)]
 pub struct Config<'a> {
diff --git a/askama_shared/src/parser.rs b/askama_shared/src/parser.rs
new file mode 100644
index 0000000..9c3358e
--- /dev/null
+++ b/askama_shared/src/parser.rs
@@ -0,0 +1,1093 @@
+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::error::ParseError;
+use nom::multi::{many0, many1, separated_list, separated_nonempty_list};
+use nom::sequence::{delimited, pair, tuple};
+use nom::{self, error_position, Compare, IResult, InputTake};
+use std::str;
+
+use crate::Syntax;
+
+#[derive(Debug)]
+pub enum Expr<'a> {
+    BoolLit(&'a str),
+    NumLit(&'a str),
+    StrLit(&'a str),
+    CharLit(&'a str),
+    Var(&'a str),
+    Path(Vec<&'a str>),
+    Array(Vec<Expr<'a>>),
+    Attr(Box<Expr<'a>>, &'a str),
+    Index(Box<Expr<'a>>, Box<Expr<'a>>),
+    Filter(&'a str, Vec<Expr<'a>>),
+    Unary(&'a str, Box<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>>),
+    RustMacro(&'a str, &'a str),
+}
+
+#[derive(Debug)]
+pub enum MatchVariant<'a> {
+    Path(Vec<&'a str>),
+    Name(&'a str),
+    NumLit(&'a str),
+    StrLit(&'a str),
+    CharLit(&'a str),
+}
+
+#[derive(Debug)]
+pub enum MatchParameter<'a> {
+    Name(&'a str),
+    NumLit(&'a str),
+    StrLit(&'a str),
+    CharLit(&'a str),
+}
+
+#[derive(Debug)]
+pub enum Target<'a> {
+    Name(&'a str),
+    Tuple(Vec<&'a str>),
+}
+
+#[derive(Clone, Copy, Debug)]
+pub struct WS(pub bool, pub bool);
+
+#[derive(Debug)]
+pub struct Macro<'a> {
+    pub ws1: WS,
+    pub args: Vec<&'a str>,
+    pub nodes: Vec<Node<'a>>,
+    pub ws2: WS,
+}
+
+#[derive(Debug)]
+pub enum Node<'a> {
+    Lit(&'a str, &'a str, &'a str),
+    Comment(WS),
+    Expr(WS, Expr<'a>),
+    Call(WS, Option<&'a str>, &'a str, Vec<Expr<'a>>),
+    LetDecl(WS, Target<'a>),
+    Let(WS, Target<'a>, Expr<'a>),
+    Cond(Vec<(WS, Option<Expr<'a>>, Vec<Node<'a>>)>, WS),
+    Match(WS, Expr<'a>, Option<&'a str>, Vec<When<'a>>, WS),
+    Loop(WS, Target<'a>, Expr<'a>, Vec<Node<'a>>, WS),
+    Extends(Expr<'a>),
+    BlockDef(WS, &'a str, Vec<Node<'a>>, WS),
+    Include(WS, &'a str),
+    Import(WS, &'a str, &'a str),
+    Macro(&'a str, Macro<'a>),
+    Raw(WS, &'a str, WS),
+}
+
+pub type Cond<'a> = (WS, Option<Expr<'a>>, Vec<Node<'a>>);
+pub type When<'a> = (
+    WS,
+    Option<MatchVariant<'a>>,
+    MatchParameters<'a>,
+    Vec<Node<'a>>,
+);
+
+#[derive(Debug)]
+pub enum MatchParameters<'a> {
+    Simple(Vec<MatchParameter<'a>>),
+    Named(Vec<(&'a str, Option<MatchParameter<'a>>)>),
+}
+
+impl<'a> Default for MatchParameters<'a> {
+    fn default() -> Self {
+        MatchParameters::Simple(vec![])
+    }
+}
+
+fn ws<F, I, O, E>(inner: F) -> impl Fn(I) -> IResult<I, O, E>
+where
+    F: Fn(I) -> IResult<I, O, E>,
+    I: InputTake + Clone + PartialEq + for<'a> Compare<&'a [u8; 1]>,
+    E: ParseError<I>,
+{
+    move |i: I| {
+        let i = alt::<_, _, (), _>((tag(b" "), tag(b"\t")))(i.clone())
+            .map(|(i, _)| i)
+            .unwrap_or(i);
+        let (i, res) = inner(i)?;
+        let i = alt::<_, _, (), _>((tag(b" "), tag(b"\t")))(i.clone())
+            .map(|(i, _)| i)
+            .unwrap_or(i);
+        Ok((i, res))
+    }
+}
+
+fn split_ws_parts(s: &[u8]) -> Node {
+    if s.is_empty() {
+        let rs = str::from_utf8(s).unwrap();
+        return Node::Lit(rs, rs, rs);
+    }
+
+    let is_ws = |c: &u8| *c != b' ' && *c != b'\t' && *c != b'\r' && *c != b'\n';
+    let start = s.iter().position(&is_ws);
+    let res = if let Some(start) = start {
+        let end = s.iter().rposition(&is_ws);
+        if let Some(end) = end {
+            (&s[..start], &s[start..=end], &s[end + 1..])
+        } else {
+            (&s[..start], &s[start..], &s[0..0])
+        }
+    } else {
+        (s, &s[0..0], &s[0..0])
+    };
+
+    Node::Lit(
+        str::from_utf8(res.0).unwrap(),
+        str::from_utf8(res.1).unwrap(),
+        str::from_utf8(res.2).unwrap(),
+    )
+}
+
+#[derive(Debug)]
+enum ContentState {
+    Start,
+    Any,
+    Brace(usize),
+    End(usize),
+}
+
+fn take_content<'a>(i: &'a [u8], s: &'a Syntax<'a>) -> ParserError<'a, Node<'a>> {
+    use crate::parser::ContentState::*;
+    let bs = s.block_start.as_bytes()[0];
+    let be = s.block_start.as_bytes()[1];
+    let cs = s.comment_start.as_bytes()[0];
+    let ce = s.comment_start.as_bytes()[1];
+    let es = s.expr_start.as_bytes()[0];
+    let ee = s.expr_start.as_bytes()[1];
+
+    let mut state = Start;
+    for (idx, c) in i.iter().enumerate() {
+        state = match state {
+            Start | Any => {
+                if *c == bs || *c == es || *c == cs {
+                    Brace(idx)
+                } else {
+                    Any
+                }
+            }
+            Brace(start) => {
+                if *c == be || *c == ee || *c == ce {
+                    End(start)
+                } else {
+                    Any
+                }
+            }
+            End(_) => panic!("cannot happen"),
+        };
+        if let End(_) = state {
+            break;
+        }
+    }
+
+    match state {
+        Any | Brace(_) => Ok((&i[..0], split_ws_parts(i))),
+        Start | End(0) => Err(nom::Err::Error(error_position!(
+            i,
+            nom::error::ErrorKind::TakeUntil
+        ))),
+        End(start) => Ok((&i[start..], split_ws_parts(&i[..start]))),
+    }
+}
+
+fn identifier(input: &[u8]) -> ParserError<&str> {
+    if !nom::character::is_alphabetic(input[0]) && input[0] != b'_' && !non_ascii(input[0]) {
+        return Err(nom::Err::Error(error_position!(
+            input,
+            nom::error::ErrorKind::AlphaNumeric
+        )));
+    }
+    for (i, ch) in input.iter().enumerate() {
+        if i == 0 || nom::character::is_alphanumeric(*ch) || *ch == b'_' || non_ascii(*ch) {
+            continue;
+        }
+        return Ok((&input[i..], str::from_utf8(&input[..i]).unwrap()));
+    }
+    Ok((&input[1..], str::from_utf8(&input[..1]).unwrap()))
+}
+
+#[inline]
+fn non_ascii(chr: u8) -> bool {
+    chr >= 0x80 && chr <= 0xFD
+}
+
+fn expr_bool_lit(i: &[u8]) -> IResult<&[u8], Expr> {
+    map(alt((tag("false"), tag("true"))), |s| {
+        Expr::BoolLit(str::from_utf8(s).unwrap())
+    })(i)
+}
+
+fn num_lit(i: &[u8]) -> IResult<&[u8], &str> {
+    map(digit1, |s| str::from_utf8(s).unwrap())(i)
+}
+
+fn expr_num_lit(i: &[u8]) -> IResult<&[u8], Expr> {
+    map(num_lit, |s| Expr::NumLit(s))(i)
+}
+
+fn expr_array_lit(i: &[u8]) -> IResult<&[u8], Expr> {
+    delimited(
+        ws(tag("[")),
+        map(separated_nonempty_list(ws(tag(",")), expr_any), |arr| {
+            Expr::Array(arr)
+        }),
+        ws(tag("]")),
+    )(i)
+}
+
+fn variant_num_lit(i: &[u8]) -> IResult<&[u8], MatchVariant> {
+    map(num_lit, |s| MatchVariant::NumLit(s))(i)
+}
+
+fn param_num_lit(i: &[u8]) -> IResult<&[u8], MatchParameter> {
+    map(num_lit, |s| MatchParameter::NumLit(s))(i)
+}
+
+fn str_lit(i: &[u8]) -> IResult<&[u8], &str> {
+    map(
+        delimited(
+            char('\"'),
+            opt(escaped(is_not("\\\""), '\\', anychar)),
+            char('\"'),
+        ),
+        |s| s.map(|s| str::from_utf8(s).unwrap()).unwrap_or(""),
+    )(i)
+}
+
+fn expr_str_lit(i: &[u8]) -> IResult<&[u8], Expr> {
+    map(str_lit, |s| Expr::StrLit(s))(i)
+}
+
+fn variant_str_lit(i: &[u8]) -> IResult<&[u8], MatchVariant> {
+    map(str_lit, |s| MatchVariant::StrLit(s))(i)
+}
+
+fn param_str_lit(i: &[u8]) -> IResult<&[u8], MatchParameter> {
+    map(str_lit, |s| MatchParameter::StrLit(s))(i)
+}
+
+fn char_lit(i: &[u8]) -> IResult<&[u8], &str> {
+    map(
+        delimited(
+            char('\''),
+            opt(escaped(is_not("\\\'"), '\\', anychar)),
+            char('\''),
+        ),
+        |s| s.map(|s| str::from_utf8(s).unwrap()).unwrap_or(""),
+    )(i)
+}
+
+fn expr_char_lit(i: &[u8]) -> IResult<&[u8], Expr> {
+    map(char_lit, |s| Expr::CharLit(s))(i)
+}
+
+fn variant_char_lit(i: &[u8]) -> IResult<&[u8], MatchVariant> {
+    map(char_lit, |s| MatchVariant::CharLit(s))(i)
+}
+
+fn param_char_lit(i: &[u8]) -> IResult<&[u8], MatchParameter> {
+    map(char_lit, |s| MatchParameter::CharLit(s))(i)
+}
+
+fn expr_var(i: &[u8]) -> IResult<&[u8], Expr> {
+    map(identifier, |s| Expr::Var(s))(i)
+}
+
+fn expr_path(i: &[u8]) -> IResult<&[u8], Expr> {
+    let tail = separated_nonempty_list(tag("::"), identifier);
+    let (i, (start, _, rest)) = tuple((identifier, tag("::"), tail))(i)?;
+
+    let mut path = vec![start];
+    path.extend(rest);
+    Ok((i, Expr::Path(path)))
+}
+
+fn variant_path(i: &[u8]) -> IResult<&[u8], MatchVariant> {
+    map(separated_nonempty_list(tag("::"), identifier), |path| {
+        MatchVariant::Path(path)
+    })(i)
+}
+
+fn target_single(i: &[u8]) -> IResult<&[u8], Target> {
+    map(identifier, |s| Target::Name(s))(i)
+}
+
+fn target_tuple(i: &[u8]) -> IResult<&[u8], Target> {
+    let parts = separated_list(tag(","), ws(identifier));
+    let trailing = opt(ws(tag(",")));
+    let full = delimited(tag("("), tuple((parts, trailing)), tag(")"));
+
+    let (i, (elems, _)) = full(i)?;
+    Ok((i, Target::Tuple(elems)))
+}
+
+fn variant_name(i: &[u8]) -> IResult<&[u8], MatchVariant> {
+    map(identifier, |s| MatchVariant::Name(s))(i)
+}
+
+fn param_name(i: &[u8]) -> IResult<&[u8], MatchParameter> {
+    map(identifier, |s| MatchParameter::Name(s))(i)
+}
+
+fn arguments(i: &[u8]) -> IResult<&[u8], Vec<Expr>> {
+    delimited(tag("("), separated_list(tag(","), ws(expr_any)), tag(")"))(i)
+}
+
+fn macro_arguments(i: &[u8]) -> IResult<&[u8], &str> {
+    delimited(char('('), nested_parenthesis, char(')'))(i)
+}
+
+fn nested_parenthesis(i: &[u8]) -> ParserError<&str> {
+    let mut nested = 0;
+    let mut last = 0;
+    let mut in_str = false;
+    let mut escaped = false;
+
+    for (i, b) in i.iter().enumerate() {
+        if !(*b == b'(' || *b == b')') || !in_str {
+            match *b {
+                b'(' => nested += 1,
+                b')' => {
+                    if nested == 0 {
+                        last = i;
+                        break;
+                    }
+                    nested -= 1;
+                }
+                b'"' => {
+                    if in_str {
+                        if !escaped {
+                            in_str = false;
+                        }
+                    } else {
+                        in_str = true;
+                    }
+                }
+                b'\\' => {
+                    escaped = !escaped;
+                }
+                _ => (),
+            }
+        }
+
+        if escaped && *b != b'\\' {
+            escaped = false;
+        }
+    }
+
+    if nested == 0 {
+        Ok((&i[last..], str::from_utf8(&i[..last]).unwrap()))
+    } else {
+        Err(nom::Err::Error(error_position!(
+            i,
+            nom::error::ErrorKind::SeparatedNonEmptyList
+        )))
+    }
+}
+
+fn parameters(i: &[u8]) -> IResult<&[u8], Vec<&str>> {
+    delimited(tag("("), separated_list(tag(","), ws(identifier)), tag(")"))(i)
+}
+
+fn with_parameters(i: &[u8]) -> IResult<&[u8], MatchParameters> {
+    let (i, (_, value)) = tuple((
+        tag("with"),
+        alt((match_simple_parameters, match_named_parameters)),
+    ))(i)?;
+    Ok((i, value))
+}
+
+fn match_simple_parameters(i: &[u8]) -> IResult<&[u8], MatchParameters> {
+    delimited(
+        ws(tag("(")),
+        map(separated_list(tag(","), ws(match_parameter)), |mps| {
+            MatchParameters::Simple(mps)
+        }),
+        tag(")"),
+    )(i)
+}
+
+fn match_named_parameters(i: &[u8]) -> IResult<&[u8], MatchParameters> {
+    delimited(
+        ws(tag("{")),
+        map(separated_list(tag(","), ws(match_named_parameter)), |mps| {
+            MatchParameters::Named(mps)
+        }),
+        tag("}"),
+    )(i)
+}
+
+fn expr_group(i: &[u8]) -> IResult<&[u8], Expr> {
+    map(delimited(char('('), expr_any, char(')')), |s| {
+        Expr::Group(Box::new(s))
+    })(i)
+}
+
+fn expr_single(i: &[u8]) -> IResult<&[u8], Expr> {
+    alt((
+        expr_bool_lit,
+        expr_num_lit,
+        expr_str_lit,
+        expr_char_lit,
+        expr_path,
+        expr_rust_macro,
+        expr_array_lit,
+        expr_var,
+        expr_group,
+    ))(i)
+}
+
+fn match_variant(i: &[u8]) -> IResult<&[u8], MatchVariant> {
+    alt((
+        variant_path,
+        variant_name,
+        variant_num_lit,
+        variant_str_lit,
+        variant_char_lit,
+    ))(i)
+}
+
+fn match_parameter(i: &[u8]) -> IResult<&[u8], MatchParameter> {
+    alt((param_name, param_num_lit, param_str_lit, param_char_lit))(i)
+}
+
+fn match_named_parameter(i: &[u8]) -> IResult<&[u8], (&str, Option<MatchParameter>)> {
+    let param = tuple((ws(tag(":")), match_parameter));
+    let (i, (name, param)) = tuple((identifier, opt(param)))(i)?;
+    Ok((i, (name, param.map(|s| s.1))))
+}
+
+fn attr(i: &[u8]) -> IResult<&[u8], (&str, Option<Vec<Expr>>)> {
+    let (i, (_, attr, args)) = tuple((tag("."), alt((num_lit, identifier)), opt(arguments)))(i)?;
+    Ok((i, (attr, args)))
+}
+
+fn expr_attr(i: &[u8]) -> IResult<&[u8], 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_index(i: &[u8]) -> IResult<&[u8], Expr> {
+    let key = opt(tuple((ws(tag("[")), expr_any, ws(tag("]")))));
+    let (i, (obj, key)) = tuple((expr_attr, key))(i)?;
+    let key = key.map(|(_, key, _)| key);
+
+    Ok((
+        i,
+        match key {
+            Some(key) => Expr::Index(Box::new(obj), Box::new(key)),
+            None => obj,
+        },
+    ))
+}
+
+fn filter(i: &[u8]) -> IResult<&[u8], (&str, Option<Vec<Expr>>)> {
+    let (i, (_, fname, args)) = tuple((tag("|"), identifier, opt(arguments)))(i)?;
+    Ok((i, (fname, args)))
+}
+
+fn expr_filtered(i: &[u8]) -> IResult<&[u8], Expr> {
+    let (i, (obj, filters)) = tuple((expr_index, many0(filter)))(i)?;
+
+    let mut res = obj;
+    for (fname, args) in filters {
+        res = Expr::Filter(fname, {
+            let mut args = match args {
+                Some(inner) => inner,
+                None => Vec::new(),
+            };
+            args.insert(0, res);
+            args
+        });
+    }
+
+    Ok((i, res))
+}
+
+fn expr_unary(i: &[u8]) -> IResult<&[u8], Expr> {
+    let (i, (op, expr)) = tuple((opt(alt((tag("!"), tag("-")))), expr_filtered))(i)?;
+    Ok((
+        i,
+        match op {
+            Some(op) => Expr::Unary(str::from_utf8(op).unwrap(), Box::new(expr)),
+            None => expr,
+        },
+    ))
+}
+
+fn expr_rust_macro(i: &[u8]) -> IResult<&[u8], Expr> {
+    let (i, (mname, _, args)) = tuple((identifier, tag("!"), macro_arguments))(i)?;
+    Ok((i, Expr::RustMacro(mname, args)))
+}
+
+macro_rules! expr_prec_layer {
+    ( $name:ident, $inner:ident, $op:expr ) => {
+        fn $name(i: &[u8]) -> IResult<&[u8], Expr> {
+            let (i, (left, op_and_right)) = tuple((
+                $inner,
+                opt(pair(
+                    ws(tag($op)),
+                    expr_any,
+                ))
+            ))(i)?;
+            Ok((i, match op_and_right {
+                Some((op, right)) => Expr::BinOp(
+                    str::from_utf8(op).unwrap(), Box::new(left), Box::new(right)
+                ),
+                None => left,
+            }))
+        }
+    };
+    ( $name:ident, $inner:ident, $( $op:expr ),+ ) => {
+        fn $name(i: &[u8]) -> IResult<&[u8], Expr> {
+            let (i, (left, op_and_right)) = tuple((
+                $inner,
+                opt(pair(
+                    ws(alt(($( tag($op) ),*,))),
+                    expr_any
+                ))
+            ))(i)?;
+            Ok((i, match op_and_right {
+                Some((op, right)) => Expr::BinOp(
+                    str::from_utf8(op).unwrap(), Box::new(left), Box::new(right)
+                ),
+                None => left,
+            }))
+        }
+    }
+}
+
+expr_prec_layer!(expr_muldivmod, expr_unary, "*", "/", "%");
+expr_prec_layer!(expr_addsub, expr_muldivmod, "+", "-");
+expr_prec_layer!(expr_shifts, expr_addsub, ">>", "<<");
+expr_prec_layer!(expr_band, expr_shifts, "&");
+expr_prec_layer!(expr_bxor, expr_band, "^");
+expr_prec_layer!(expr_bor, expr_bxor, "|");
+expr_prec_layer!(expr_compare, expr_bor, "==", "!=", ">=", ">", "<=", "<");
+expr_prec_layer!(expr_and, expr_compare, "&&");
+expr_prec_layer!(expr_or, expr_and, "||");
+
+fn range_right(i: &[u8]) -> IResult<&[u8], Expr> {
+    let (i, (_, incl, right)) = tuple((ws(tag("..")), opt(ws(tag("="))), opt(expr_or)))(i)?;
+    Ok((
+        i,
+        Expr::Range(
+            if incl.is_some() { "..=" } else { ".." },
+            None,
+            right.map(Box::new),
+        ),
+    ))
+}
+
+fn expr_any(i: &[u8]) -> IResult<&[u8], Expr> {
+    let compound = map(tuple((expr_or, range_right)), |(left, rest)| match rest {
+        Expr::Range(op, _, right) => Expr::Range(op, Some(Box::new(left)), right),
+        _ => unreachable!(),
+    });
+    let p = alt((range_right, compound, expr_or));
+    Ok(p(i)?)
+}
+
+fn expr_node<'a>(i: &'a [u8], s: &'a Syntax<'a>) -> IResult<&'a [u8], Node<'a>> {
+    let p = tuple((
+        |i| tag_expr_start(i, s),
+        opt(tag("-")),
+        ws(expr_any),
+        opt(tag("-")),
+        |i| tag_expr_end(i, s),
+    ));
+    let (i, (_, pws, expr, nws, _)) = p(i)?;
+    Ok((i, Node::Expr(WS(pws.is_some(), nws.is_some()), expr)))
+}
+
+fn block_call(i: &[u8]) -> IResult<&[u8], Node> {
+    let p = tuple((
+        opt(tag("-")),
+        ws(tag("call")),
+        opt(tuple((ws(identifier), ws(tag("::"))))),
+        ws(identifier),
+        ws(arguments),
+        opt(tag("-")),
+    ));
+    let (i, (pws, _, scope, name, args, nws)) = p(i)?;
+    let scope = scope.map(|(scope, _)| scope);
+    Ok((
+        i,
+        Node::Call(WS(pws.is_some(), nws.is_some()), scope, name, args),
+    ))
+}
+
+fn cond_if(i: &[u8]) -> IResult<&[u8], Expr> {
+    let (i, (_, cond)) = tuple((ws(tag("if")), ws(expr_any)))(i)?;
+    Ok((i, cond))
+}
+
+fn cond_block<'a>(i: &'a [u8], s: &'a Syntax<'a>) -> IResult<&'a [u8], Cond<'a>> {
+    let p = tuple((
+        |i| tag_block_start(i, s),
+        opt(tag("-")),
+        ws(tag("else")),
+        opt(cond_if),
+        opt(tag("-")),
+        |i| tag_block_end(i, s),
+        |i| parse_template(i, s),
+    ));
+    let (i, (_, pws, _, cond, nws, _, block)) = p(i)?;
+    Ok((i, (WS(pws.is_some(), nws.is_some()), cond, block)))
+}
+
+fn block_if<'a>(i: &'a [u8], s: &'a Syntax<'a>) -> IResult<&'a [u8], Node<'a>> {
+    let p = tuple((
+        opt(tag("-")),
+        cond_if,
+        opt(tag("-")),
+        |i| tag_block_end(i, s),
+        |i| parse_template(i, s),
+        many0(|i| cond_block(i, s)),
+        |i| tag_block_start(i, s),
+        opt(tag("-")),
+        ws(tag("endif")),
+        opt(tag("-")),
+    ));
+    let (i, (pws1, cond, nws1, _, block, elifs, _, pws2, _, nws2)) = p(i)?;
+
+    let mut res = Vec::new();
+    res.push((WS(pws1.is_some(), nws1.is_some()), Some(cond), block));
+    res.extend(elifs);
+    Ok((i, Node::Cond(res, WS(pws2.is_some(), nws2.is_some()))))
+}
+
+fn match_else_block<'a>(i: &'a [u8], s: &'a Syntax<'a>) -> IResult<&'a [u8], When<'a>> {
+    let p = tuple((
+        |i| tag_block_start(i, s),
+        opt(tag("-")),
+        ws(tag("else")),
+        opt(tag("-")),
+        |i| tag_block_end(i, s),
+        |i| parse_template(i, s),
+    ));
+    let (i, (_, pws, _, nws, _, block)) = p(i)?;
+    Ok((
+        i,
+        (
+            WS(pws.is_some(), nws.is_some()),
+            None,
+            MatchParameters::Simple(vec![]),
+            block,
+        ),
+    ))
+}
+
+fn when_block<'a>(i: &'a [u8], s: &'a Syntax<'a>) -> IResult<&'a [u8], When<'a>> {
+    let p = tuple((
+        |i| tag_block_start(i, s),
+        opt(tag("-")),
+        ws(tag("when")),
+        ws(match_variant),
+        opt(ws(with_parameters)),
+        opt(tag("-")),
+        |i| tag_block_end(i, s),
+        |i| parse_template(i, s),
+    ));
+    let (i, (_, pws, _, variant, params, nws, _, block)) = p(i)?;
+    Ok((
+        i,
+        (
+            WS(pws.is_some(), nws.is_some()),
+            Some(variant),
+            params.unwrap_or_default(),
+            block,
+        ),
+    ))
+}
+
+fn block_match<'a>(i: &'a [u8], s: &'a Syntax<'a>) -> IResult<&'a [u8], Node<'a>> {
+    let p = tuple((
+        opt(tag("-")),
+        ws(tag("match")),
+        ws(expr_any),
+        opt(tag("-")),
+        |i| tag_block_end(i, s),
+        opt(|i| take_content(i, s)),
+        many1(|i| when_block(i, s)),
+        opt(|i| match_else_block(i, s)),
+        ws(|i| tag_block_start(i, s)),
+        opt(tag("-")),
+        ws(tag("endmatch")),
+        opt(tag("-")),
+    ));
+    let (i, (pws1, _, expr, nws1, _, inter, arms, else_arm, _, pws2, _, nws2)) = p(i)?;
+
+    let mut arms = arms;
+    if let Some(arm) = else_arm {
+        arms.push(arm);
+    }
+
+    let inter = match inter {
+        Some(Node::Lit(lws, val, rws)) => {
+            assert!(
+                val.is_empty(),
+                "only whitespace allowed between match and first when, found {}",
+                val
+            );
+            assert!(
+                rws.is_empty(),
+                "only whitespace allowed between match and first when, found {}",
+                rws
+            );
+            Some(lws)
+        }
+        None => None,
+        _ => panic!("only literals allowed between match and first when"),
+    };
+
+    Ok((
+        i,
+        Node::Match(
+            WS(pws1.is_some(), nws1.is_some()),
+            expr,
+            inter,
+            arms,
+            WS(pws2.is_some(), nws2.is_some()),
+        ),
+    ))
+}
+
+fn block_let(i: &[u8]) -> IResult<&[u8], Node> {
+    let p = tuple((
+        opt(tag("-")),
+        ws(tag("let")),
+        ws(alt((target_single, target_tuple))),
+        opt(tuple((ws(tag("=")), ws(expr_any)))),
+        opt(tag("-")),
+    ));
+    let (i, (pws, _, var, val, nws)) = p(i)?;
+
+    Ok((
+        i,
+        if let Some((_, val)) = val {
+            Node::Let(WS(pws.is_some(), nws.is_some()), var, val)
+        } else {
+            Node::LetDecl(WS(pws.is_some(), nws.is_some()), var)
+        },
+    ))
+}
+
+fn block_for<'a>(i: &'a [u8], s: &'a Syntax<'a>) -> IResult<&'a [u8], Node<'a>> {
+    let p = tuple((
+        opt(tag("-")),
+        ws(tag("for")),
+        ws(alt((target_single, target_tuple))),
+        ws(tag("in")),
+        ws(expr_any),
+        opt(tag("-")),
+        |i| tag_block_end(i, s),
+        |i| parse_template(i, s),
+        |i| tag_block_start(i, s),
+        opt(tag("-")),
+        ws(tag("endfor")),
+        opt(tag("-")),
+    ));
+    let (i, (pws1, _, var, _, iter, nws1, _, block, _, pws2, _, nws2)) = p(i)?;
+    Ok((
+        i,
+        Node::Loop(
+            WS(pws1.is_some(), nws1.is_some()),
+            var,
+            iter,
+            block,
+            WS(pws2.is_some(), nws2.is_some()),
+        ),
+    ))
+}
+
+fn block_extends(i: &[u8]) -> IResult<&[u8], Node> {
+    let (i, (_, name)) = tuple((ws(tag("extends")), ws(expr_str_lit)))(i)?;
+    Ok((i, Node::Extends(name)))
+}
+
+fn block_block<'a>(i: &'a [u8], s: &'a Syntax<'a>) -> IResult<&'a [u8], Node<'a>> {
+    let start = tuple((
+        opt(tag("-")),
+        ws(tag("block")),
+        ws(identifier),
+        opt(tag("-")),
+        |i| tag_block_end(i, s),
+        |i| parse_template(i, s),
+    ));
+    let (i, (pws1, _, name, nws1, _, contents)) = start(i)?;
+
+    let end = tuple((
+        |i| tag_block_start(i, s),
+        opt(tag("-")),
+        ws(tag("endblock")),
+        opt(ws(tag(name))),
+        opt(tag("-")),
+    ));
+    let (i, (_, pws2, _, _, nws2)) = end(i)?;
+
+    Ok((
+        i,
+        Node::BlockDef(
+            WS(pws1.is_some(), nws1.is_some()),
+            name,
+            contents,
+            WS(pws2.is_some(), nws2.is_some()),
+        ),
+    ))
+}
+
+fn block_include(i: &[u8]) -> IResult<&[u8], Node> {
+    let p = tuple((
+        opt(tag("-")),
+        ws(tag("include")),
+        ws(expr_str_lit),
+        opt(tag("-")),
+    ));
+    let (i, (pws, _, name, nws)) = p(i)?;
+    Ok((
+        i,
+        Node::Include(
+            WS(pws.is_some(), nws.is_some()),
+            match name {
+                Expr::StrLit(s) => s,
+                _ => panic!("include path must be a string literal"),
+            },
+        ),
+    ))
+}
+
+fn block_import(i: &[u8]) -> IResult<&[u8], Node> {
+    let p = tuple((
+        opt(tag("-")),
+        ws(tag("import")),
+        ws(expr_str_lit),
+        ws(tag("as")),
+        ws(identifier),
+        opt(tag("-")),
+    ));
+    let (i, (pws, _, name, _, scope, nws)) = p(i)?;
+    Ok((
+        i,
+        Node::Import(
+            WS(pws.is_some(), nws.is_some()),
+            match name {
+                Expr::StrLit(s) => s,
+                _ => panic!("import path must be a string literal"),
+            },
+            scope,
+        ),
+    ))
+}
+
+fn block_macro<'a>(i: &'a [u8], s: &'a Syntax<'a>) -> IResult<&'a [u8], Node<'a>> {
+    let p = tuple((
+        opt(tag("-")),
+        ws(tag("macro")),
+        ws(identifier),
+        ws(parameters),
+        opt(tag("-")),
+        |i| tag_block_end(i, s),
+        |i| parse_template(i, s),
+        |i| tag_block_start(i, s),
+        opt(tag("-")),
+        ws(tag("endmacro")),
+        opt(tag("-")),
+    ));
+
+    let (i, (pws1, _, name, params, nws1, _, contents, _, pws2, _, nws2)) = p(i)?;
+    if name == "super" {
+        panic!("invalid macro name 'super'");
+    }
+
+    Ok((
+        i,
+        Node::Macro(
+            name,
+            Macro {
+                ws1: WS(pws1.is_some(), nws1.is_some()),
+                args: params,
+                nodes: contents,
+                ws2: WS(pws2.is_some(), nws2.is_some()),
+            },
+        ),
+    ))
+}
+
+fn block_raw<'a>(i: &'a [u8], s: &'a Syntax<'a>) -> IResult<&'a [u8], Node<'a>> {
+    let p = tuple((
+        opt(tag("-")),
+        ws(tag("raw")),
+        opt(tag("-")),
+        |i| tag_block_end(i, s),
+        take_until("{% endraw %}"),
+        |i| tag_block_start(i, s),
+        opt(tag("-")),
+        ws(tag("endraw")),
+        opt(tag("-")),
+    ));
+
+    let (i, (pws1, _, nws1, _, contents, _, pws2, _, nws2)) = p(i)?;
+    let str_contents = str::from_utf8(contents).unwrap();
+    Ok((
+        i,
+        Node::Raw(
+            WS(pws1.is_some(), nws1.is_some()),
+            str_contents,
+            WS(pws2.is_some(), nws2.is_some()),
+        ),
+    ))
+}
+
+fn block_node<'a>(i: &'a [u8], s: &'a Syntax<'a>) -> IResult<&'a [u8], Node<'a>> {
+    let p = tuple((
+        |i| tag_block_start(i, s),
+        alt((
+            block_call,
+            block_let,
+            |i| block_if(i, s),
+            |i| block_for(i, s),
+            |i| block_match(i, s),
+            block_extends,
+            block_include,
+            block_import,
+            |i| block_block(i, s),
+            |i| block_macro(i, s),
+            |i| block_raw(i, s),
+        )),
+        |i| tag_block_end(i, s),
+    ));
+    let (i, (_, contents, _)) = p(i)?;
+    Ok((i, contents))
+}
+
+fn block_comment<'a>(i: &'a [u8], s: &'a Syntax<'a>) -> IResult<&'a [u8], Node<'a>> {
+    let p = tuple((
+        |i| tag_comment_start(i, s),
+        opt(tag("-")),
+        take_until(s.comment_end),
+        |i| tag_comment_end(i, s),
+    ));
+    let (i, (_, pws, inner, _)) = p(i)?;
+    Ok((
+        i,
+        Node::Comment(WS(
+            pws.is_some(),
+            inner.len() > 1 && inner[inner.len() - 1] == b'-',
+        )),
+    ))
+}
+
+fn parse_template<'a>(i: &'a [u8], s: &'a Syntax<'a>) -> IResult<&'a [u8], Vec<Node<'a>>> {
+    many0(alt((
+        complete(|i| take_content(i, s)),
+        complete(|i| block_comment(i, s)),
+        complete(|i| expr_node(i, s)),
+        complete(|i| block_node(i, s)),
+    )))(i)
+}
+
+fn tag_block_start<'a>(i: &'a [u8], s: &'a Syntax<'a>) -> IResult<&'a [u8], &'a [u8]> {
+    tag(s.block_start)(i)
+}
+fn tag_block_end<'a>(i: &'a [u8], s: &'a Syntax<'a>) -> IResult<&'a [u8], &'a [u8]> {
+    tag(s.block_end)(i)
+}
+fn tag_comment_start<'a>(i: &'a [u8], s: &'a Syntax<'a>) -> IResult<&'a [u8], &'a [u8]> {
+    tag(s.comment_start)(i)
+}
+fn tag_comment_end<'a>(i: &'a [u8], s: &'a Syntax<'a>) -> IResult<&'a [u8], &'a [u8]> {
+    tag(s.comment_end)(i)
+}
+fn tag_expr_start<'a>(i: &'a [u8], s: &'a Syntax<'a>) -> IResult<&'a [u8], &'a [u8]> {
+    tag(s.expr_start)(i)
+}
+fn tag_expr_end<'a>(i: &'a [u8], s: &'a Syntax<'a>) -> IResult<&'a [u8], &'a [u8]> {
+    tag(s.expr_end)(i)
+}
+
+pub fn parse<'a>(src: &'a str, syntax: &'a Syntax<'a>) -> Vec<Node<'a>> {
+    match parse_template(src.as_bytes(), syntax) {
+        Ok((left, res)) => {
+            if !left.is_empty() {
+                let s = str::from_utf8(left).unwrap();
+                panic!("unable to parse template:\n\n{:?}", s);
+            } else {
+                res
+            }
+        }
+        Err(nom::Err::Error(err)) => panic!("problems parsing template source: {:?}", err),
+        Err(nom::Err::Failure(err)) => panic!("problems parsing template source: {:?}", err),
+        Err(nom::Err::Incomplete(_)) => panic!("parsing incomplete"),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::Syntax;
+
+    fn check_ws_split(s: &str, res: &(&str, &str, &str)) {
+        let node = super::split_ws_parts(s.as_bytes());
+        match node {
+            super::Node::Lit(lws, s, rws) => {
+                assert_eq!(lws, res.0);
+                assert_eq!(s, res.1);
+                assert_eq!(rws, res.2);
+            }
+            _ => {
+                panic!("fail");
+            }
+        }
+    }
+
+    #[test]
+    fn test_ws_splitter() {
+        check_ws_split("", &("", "", ""));
+        check_ws_split("a", &("", "a", ""));
+        check_ws_split("\ta", &("\t", "a", ""));
+        check_ws_split("b\n", &("", "b", "\n"));
+        check_ws_split(" \t\r\n", &(" \t\r\n", "", ""));
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_invalid_block() {
+        super::parse("{% extend \"blah\" %}", &Syntax::default());
+    }
+
+    #[test]
+    fn test_parse_filter() {
+        super::parse("{{ strvar|e }}", &Syntax::default());
+    }
+
+    #[test]
+    fn change_delimiters_parse_filter() {
+        let syntax = Syntax {
+            expr_start: "{~",
+            expr_end: "~}",
+            ..Syntax::default()
+        };
+
+        super::parse("{~ strvar|e ~}", &syntax);
+    }
+}
+
+type ParserError<'a, T> = Result<(&'a [u8], T), nom::Err<(&'a [u8], nom::error::ErrorKind)>>;