ructe 0.3.14

Rust Compiled Templates, efficient type-safe templates.
Documentation
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use expression::{comma_expressions, expression, rust_name};
use spacelike::{comment, spacelike};
use std::fmt::{self, Display};
use std::str::from_utf8;

/// Copied from nom, but fixed for
/// <https://github.com/Geal/nom/issues/463>
///
/// This should be removed when a fix for that is released from nom.
macro_rules! my_many_till(
  ($i:expr, $submac1:ident!( $($args1:tt)* ), $submac2:ident!( $($args2:tt)* ))
        => (
    {
      use nom::InputLength;
      use nom::ErrorKind;
      use nom::IResult;
      use nom::Needed;

      let ret;
      let mut res   = ::std::vec::Vec::new();
      let mut input = $i;

      loop {
        match $submac2!(input, $($args2)*) {
          IResult::Done(i, o) => {
            ret = IResult::Done(i, (res, o));
            break;
          },
          _                           => {
            match $submac1!(input, $($args1)*) {
              IResult::Error(err)                            => {
                ret = IResult::Error(error_node_position!(ErrorKind::ManyTill,
                                                          input,
                                                          err));
                break;
              },
              IResult::Incomplete(Needed::Unknown) => {
                ret = IResult::Incomplete(Needed::Unknown);
                break;
              },
              IResult::Incomplete(Needed::Size(i)) => {
                let size = i + ($i).input_len() - input.input_len();
                ret = IResult::Incomplete(Needed::Size(size));
                break;
              },
              IResult::Done(i, o)                          => {
                // loop trip must always consume (otherwise infinite loops)
                if i == input {
                  ret = IResult::Error(error_position!(ErrorKind::ManyTill,
                                                       input));
                  break;
                }

                res.push(o);
                input = i;
              },
            }
          },
        }
      }

      ret
    }
  );
  ($i:expr, $f:expr, $g: expr) => (
    my_many_till!($i, call!($f), call!($g));
  );
);

#[derive(Debug, PartialEq, Eq)]
pub enum TemplateExpression {
    Comment,
    Text {
        text: String,
    },
    Expression {
        expr: String,
    },
    ForLoop {
        name: String,
        expr: String,
        body: Vec<TemplateExpression>,
    },
    IfBlock {
        expr: String,
        body: Vec<TemplateExpression>,
        else_body: Option<Vec<TemplateExpression>>,
    },
    CallTemplate {
        name: String,
        args: Vec<TemplateArgument>,
    },
}

#[derive(Debug, PartialEq, Eq)]
pub enum TemplateArgument {
    Rust(String),
    Body(Vec<TemplateExpression>),
}

impl Display for TemplateArgument {
    fn fmt(&self, out: &mut fmt::Formatter) -> Result<(), fmt::Error> {
        match *self {
            TemplateArgument::Rust(ref s) => write!(out, "{}", s),
            TemplateArgument::Body(ref v) => write!(
                out,
                "|out| {{\n{}\nOk(())\n}}\n",
                v.iter().map(|b| b.code()).collect::<String>(),
            ),
        }
    }
}

impl TemplateExpression {
    pub fn text(text: &str) -> Self {
        TemplateExpression::Text {
            text: text.to_string(),
        }
    }
    pub fn code(&self) -> String {
        match *self {
            TemplateExpression::Comment => String::new(),
            TemplateExpression::Text { ref text } => {
                format!("write!(out, {:?})?;\n", text)
            }
            TemplateExpression::Expression { ref expr } => {
                format!("{}.to_html(out)?;\n", expr)
            }
            TemplateExpression::ForLoop {
                ref name,
                ref expr,
                ref body,
            } => format!(
                "for {} in {} {{\n{}}}\n",
                name,
                expr,
                body.iter().map(|b| b.code()).collect::<String>(),
            ),
            TemplateExpression::IfBlock {
                ref expr,
                ref body,
                ref else_body,
            } => format!(
                "if {} {{\n{}}}{}\n",
                expr,
                body.iter().map(|b| b.code()).collect::<String>(),
                else_body
                    .iter()
                    .map(|b| format!(
                        " else {{\n{}}}",
                        b.iter().map(|b| b.code()).collect::<String>(),
                    ))
                    .collect::<String>(),
            ),
            TemplateExpression::CallTemplate { ref name, ref args } => {
                format!(
                    "{}(out{})?;\n",
                    name,
                    args.iter()
                        .map(|b| format!(", {}", b))
                        .collect::<String>(),
                )
            }
        }
    }
}

named!(
    pub template_expression<&[u8], TemplateExpression>,
    add_return_error!(
        err_str!("In expression starting here"),
        switch!(
            opt!(preceded!(tag!("@"),
                           alt!(tag!(":") | tag!("{") | tag!("}") |
                                terminated!(
                                    alt!(tag!("if") | tag!("for")),
                                    tag!(" ")) |
                                value!(&b""[..])))),
            Some(b":") => map!(
                pair!(rust_name,
                      delimited!(tag!("("),
                                 separated_list!(tag!(", "), template_argument),
                                 tag!(")"))),
                |(name, args)| TemplateExpression::CallTemplate {
                    name: name,
                    args: args,
                }) |
            Some(b"{") => value!(TemplateExpression::text("{{")) |
            Some(b"}") => value!(TemplateExpression::text("}}")) |
            Some(b"if") => return_error!(
                err_str!("Error in conditional expression:"),
                map!(
                    tuple!(
                        delimited!(spacelike, cond_expression, spacelike),
                        template_block,
                        opt!(complete!(preceded!(
                            delimited!(spacelike, tag!("else"), spacelike),
                            template_block
                        )))
                    ),
                    |(expr, body, else_body)| TemplateExpression::IfBlock {
                        expr: expr,
                        body: body,
                        else_body: else_body,
                    })) |
            Some(b"for") => map!(
                tuple!(
                    delimited!(
                        spacelike,
                        return_error!(
                            err_str!("Expected loop variable name \
                                      or destructuring tuple"),
                            alt!(rust_name |
                                 map!(
                                     pair!(
                                         opt!(char!('&')),
                                         delimited!(tag!("("),
                                                    comma_expressions,
                                                    tag!(")"))
                                     ),
                                     |(pre, args)| match pre {
                                         Some(_) => format!("&({})", args),
                                         None => format!("({})", args)
                                     }
                                 ))),
                        spacelike),
                    delimited!(
                        terminated!(return_error!(err_str!("Expected \"in\""),
                                                  tag!("in")),
                                    spacelike),
                        return_error!(err_str!("Expected iterable expression"),
                                      expression),
                        spacelike),
                    terminated!(
                        return_error!(err_str!("Error in loop block:"),
                                      template_block),
                        spacelike)),
                |(name, expr, body)| TemplateExpression::ForLoop {
                    name: name,
                    expr: expr,
                    body: body,
                }) |
            Some(b"") => map!(
                expression,
                |expr| TemplateExpression::Expression{ expr: expr }
            ) |
            None => alt!(
                map!(comment, |()| TemplateExpression::Comment) |
                map!(is_not!("@{}"),
                     |text| TemplateExpression::Text {
                         text: from_utf8(text).unwrap().to_string()
                     })
            )
    ))
);

named!(template_block<&[u8], Vec<TemplateExpression>>,
       preceded!(
           return_error!(err_str!("Expected \"{\""), char!('{')),
           map!(
               my_many_till!(
                   return_error!(
                       err_str!("Error in expression starting here:"),
                       template_expression),
                   char!('}')),
               |(block, _end)| block
)));

named!(template_argument<&[u8], TemplateArgument>,
       alt!(map!(delimited!(tag!("{"), many0!(template_expression), tag!("}")),
                 TemplateArgument::Body) |
            map!(expression, TemplateArgument::Rust)));

named!(
    cond_expression<&[u8], String>,
    switch!(
        opt!(tag!("let")),
        Some(b"let") => map!(
            pair!(
                preceded!(spacelike,
                          return_error!(
                              err_str!("Expected LHS expression in let binding"),
                              expression)),
                preceded!(
                    delimited!(
                        spacelike,
                        return_error!(err_str!("Expected \"=\""), char!('=')),
                        spacelike),
                    return_error!(
                        err_str!("Expected RHS expression in let binding"),
                        expression))),
            |(lhs, rhs)| format!("let {} = {}", lhs, rhs)) |
        None => map!(
            pair!(
                return_error!(err_str!("Expected expression"), expression),
                opt!(pair!(rel_operator, expression))),
            |(a, b)| if let Some((op, rhs)) = b {
                format!("{} {} {}", a, op, rhs)
            } else {
                a
            })
    )
);

named!(rel_operator<&[u8], &str>,
       map!(
           delimited!(
               spacelike,
               alt!(tag_s!("==") | tag_s!("!=") | tag_s!(">=") |
                    tag_s!(">") | tag_s!("<=") | tag_s!("<")),
               spacelike),
           |s| from_utf8(s).unwrap()
       )
);

#[cfg(test)]
mod test {
    use super::*;
    use super::super::show_errors;
    use nom::IResult;

    #[test]
    fn if_boolean_var() {
        assert_eq!(
            template_expression(b"@if cond { something }"),
            IResult::Done(
                &b""[..],
                TemplateExpression::IfBlock {
                    expr: "cond".to_string(),
                    body: vec![TemplateExpression::text(" something ")],
                    else_body: None,
                }
            )
        )
    }

    #[test]
    fn if_let() {
        assert_eq!(
            template_expression(b"@if let Some(x) = x { something }"),
            IResult::Done(
                &b""[..],
                TemplateExpression::IfBlock {
                    expr: "let Some(x) = x".to_string(),
                    body: vec![TemplateExpression::text(" something ")],
                    else_body: None,
                }
            )
        )
    }

    #[test]
    fn if_let_2() {
        assert_eq!(
            template_expression(b"@if let Some((x,y)) = x { something }"),
            IResult::Done(
                &b""[..],
                TemplateExpression::IfBlock {
                    expr: "let Some((x, y)) = x".to_string(),
                    body: vec![TemplateExpression::text(" something ")],
                    else_body: None,
                }
            )
        )
    }

    #[test]
    fn if_compare() {
        assert_eq!(
            template_expression(b"@if x == 17 { something }"),
            IResult::Done(
                &b""[..],
                TemplateExpression::IfBlock {
                    expr: "x == 17".to_string(),
                    body: vec![TemplateExpression::text(" something ")],
                    else_body: None,
                }
            )
        )
    }

    #[test]
    fn if_missing_conditional() {
        assert_eq!(
            expression_error(b"@if { oops }"),
            ":   1:@if { oops }\n\
             :         ^ Error in conditional expression:\n\
             :   1:@if { oops }\n\
             :         ^ Expected expression\n\
             :   1:@if { oops }\n\
             :         ^ Expected rust expression\n\
             :   1:@if { oops }\n\
             :         ^ Alt\n"
        )
    }

    #[test]
    fn if_bad_let() {
        assert_eq!(
            expression_error(b"@if let foo { oops }"),
            ":   1:@if let foo { oops }\n\
             :         ^ Error in conditional expression:\n\
             :   1:@if let foo { oops }\n\
             :                 ^ Expected \"=\"\n\
             :   1:@if let foo { oops }\n\
             :                 ^ Char\n"
        )
    }

    #[test]
    fn for_missig_in() {
        // TODO The second part of this message isn't really helpful.
        assert_eq!(
            expression_error(b"@for what ever { hello }"),
            ":   1:@for what ever { hello }\n\
             :               ^ Expected \"in\"\n\
             :   1:@for what ever { hello }\n\
             :               ^ Tag\n"
        )
    }

    fn expression_error(input: &[u8]) -> String {
        let mut buf = Vec::new();
        show_errors(&mut buf, input, template_expression(input), ":");
        String::from_utf8(buf).unwrap()
    }
}