Properly recover from errors

Signed-off-by: Marcel Müller <neikos@neikos.email>

src/eval/mod.rs

@@ -0,0 +1,7 @@
+pub struct EvalStack {
+    stack: Vec<Evaluation>,
+}
+
+pub enum Evaluation {
+    AppendContent { content: String },
+}

src/lib.rs

@@ -6,6 +6,7 @@ use serde::Serialize;
 use thiserror::Error;
 
 pub mod parser;
+pub mod eval;
 
 #[derive(Debug, Error, Display)]
 pub enum TempleError {

src/parser/mod.rs

@@ -8,13 +8,9 @@ use annotate_snippets::Snippet;
 use winnow::LocatingSlice;
 use winnow::Parser;
 use winnow::RecoverableParser;
-use winnow::ascii::alpha1;
-use winnow::ascii::multispace0;
 use winnow::ascii::multispace1;
 use winnow::combinator::alt;
-use winnow::combinator::cut_err;
 use winnow::combinator::eof;
-use winnow::combinator::opt;
 use winnow::combinator::peek;
 use winnow::combinator::repeat_till;
 use winnow::combinator::terminated;
@@ -27,8 +23,10 @@ use winnow::stream::Location;
 use winnow::stream::Recoverable;
 use winnow::stream::Stream;
 use winnow::token::any;
+use winnow::token::one_of;
 use winnow::token::rest;
 use winnow::token::take_until;
+use winnow::token::take_while;
 
 type Input<'input> = Recoverable<LocatingSlice<&'input str>, ParseError>;
 type PResult<'input, T> = Result<T, ParseError>;
@@ -53,35 +51,37 @@ impl ParseFailure {
     }
 
     pub fn to_report(&self) -> String {
-        let mut report = String::new();
+        let reports = self
+            .errors
+            .iter()
+            .map(|error| {
+                Level::ERROR
+                    .primary_title(
+                        error
+                            .message
+                            .as_deref()
+                            .unwrap_or("An error occurred while parsing"),
+                    )
+                    .element(
+                        Snippet::source(self.source.as_ref()).annotation(
+                            AnnotationKind::Primary
+                                .span(error.span.clone().map(|s| s.range).unwrap_or_else(|| 0..0)),
+                        ),
+                    )
+                    .elements(error.help.as_ref().map(|help| Level::HELP.message(help)))
+            })
+            .collect::<Vec<_>>();
 
-        for error in &self.errors {
-            let rep = &[Level::ERROR
-                .primary_title(
-                    error
-                        .message
-                        .as_deref()
-                        .unwrap_or("An error occurred while parsing"),
-                )
-                .element(
-                    Snippet::source(self.source.as_ref()).annotation(
-                        AnnotationKind::Primary
-                            .span(error.span.clone().map(|s| s.range).unwrap_or_else(|| 0..0)),
-                    ),
-                )];
-
-            let renderer =
-                Renderer::styled().decor_style(annotate_snippets::renderer::DecorStyle::Unicode);
-            report.push_str(&renderer.render(rep));
-        }
-
-        report
+        let renderer =
+            Renderer::styled().decor_style(annotate_snippets::renderer::DecorStyle::Unicode);
+        renderer.render(&reports)
     }
 }
 
 #[derive(Debug, Clone)]
 pub struct ParseError {
     pub(crate) message: Option<String>,
+    pub(crate) help: Option<String>,
     pub(crate) span: Option<SourceSpan>,
 
     is_fatal: bool,
@@ -91,6 +91,7 @@ impl ParseError {
     fn ctx() -> Self {
         ParseError {
             message: None,
+            help: None,
             span: None,
 
             is_fatal: false,
@@ -101,6 +102,11 @@ impl ParseError {
         self.message = Some(message.to_string());
         self
     }
+
+    fn help(mut self, help: &str) -> Self {
+        self.help = Some(help.to_string());
+        self
+    }
 }
 
 impl ModalError for ParseError {
@@ -138,6 +144,7 @@ impl<'input> AddContext<Input<'input>, ParseError> for ParseError {
         context: ParseError,
     ) -> Self {
         self.message = context.message.or(self.message);
+        self.help = context.help.or(self.help);
         self
     }
 }
@@ -157,11 +164,7 @@ impl<'input> ParserError<Input<'input>> for ParseError {
     type Inner = ParseError;
 
     fn from_input(_input: &Input<'input>) -> Self {
-        ParseError {
-            message: None,
-            span: None,
-            is_fatal: false,
-        }
+        ParseError::ctx()
     }
 
     fn into_inner(self) -> winnow::Result<Self::Inner, Self> {
@@ -175,111 +178,131 @@ impl<'input> ParserError<Input<'input>> for ParseError {
 
 #[derive(Debug)]
 pub struct ParsedTemplate<'input> {
-    content: Vec<TemplateChunk<'input>>,
+    tokens: Vec<TemplateToken<'input>>,
 }
 
-#[derive(Debug)]
-pub enum TemplateChunk<'input> {
+impl<'input> ParsedTemplate<'input> {
+    pub fn tokens(&self) -> &[TemplateToken<'input>] {
+        &self.tokens
+    }
+}
+
+#[derive(Debug, Clone)]
+pub enum TemplateToken<'input> {
     Content(&'input str),
-    Expression(InterpolateExpression<'input>),
-}
-
-#[derive(Debug)]
-pub struct InterpolateExpression<'input> {
-    pub left_delim: &'input str,
-    pub wants_output: Option<&'input str>,
-    pub value: Box<TemplateExpression<'input>>,
-    pub right_delim: &'input str,
-}
-
-#[derive(Debug)]
-pub struct TemplateExpression<'input> {
-    pub before_ws: &'input str,
-    pub expr: TemplateExpr<'input>,
-    pub after_ws: &'input str,
-}
-
-#[derive(Debug)]
-pub enum TemplateExpr<'input> {
-    Variable(&'input str),
+    LeftDelim(&'input str),
+    RightDelim(&'input str),
+    WantsOutput(&'input str),
+    Ident(&'input str),
+    Whitespace(&'input str),
+    Invalid(&'input str),
 }
 
 pub fn parse(input: &str) -> Result<ParsedTemplate<'_>, ParseFailure> {
-    let (_remaining, val, errors) = parse_chunks.recoverable_parse(LocatingSlice::new(input));
-
-    dbg!(&val);
+    let (_remaining, val, errors) = parse_tokens.recoverable_parse(LocatingSlice::new(input));
 
     if errors.is_empty()
         && let Some(val) = val
     {
-        Ok(ParsedTemplate { content: val })
+        Ok(ParsedTemplate { tokens: val })
     } else {
         Err(ParseFailure::from_errors(errors, input))
     }
 }
 
-fn parse_chunks<'input>(input: &mut Input<'input>) -> PResult<'input, Vec<TemplateChunk<'input>>> {
+fn parse_tokens<'input>(input: &mut Input<'input>) -> PResult<'input, Vec<TemplateToken<'input>>> {
     repeat_till(0.., alt((parse_interpolate, parse_content)), eof)
-        .map(|(v, _)| v)
+        .map(|(v, _): (Vec<_>, _)| v.into_iter().flatten().collect())
         .parse_next(input)
 }
 
-fn parse_content<'input>(input: &mut Input<'input>) -> PResult<'input, TemplateChunk<'input>> {
+fn parse_content<'input>(input: &mut Input<'input>) -> PResult<'input, Vec<TemplateToken<'input>>> {
     alt((take_until(1.., "{{"), rest))
-        .map(TemplateChunk::Content)
+        .map(TemplateToken::Content)
+        .map(|v| vec![v])
         .parse_next(input)
 }
 
-fn parse_interpolate<'input>(input: &mut Input<'input>) -> PResult<'input, TemplateChunk<'input>> {
-    let left_delim = "{{".parse_next(input)?;
-    let (wants_output, value, right_delim) =
-        cut_err((opt("="), parse_value.map(Box::new), "}}")).parse_next(input)?;
+fn parse_interpolate<'input>(
+    input: &mut Input<'input>,
+) -> PResult<'input, Vec<TemplateToken<'input>>> {
+    let left_delim = "{{".map(TemplateToken::LeftDelim).parse_next(input)?;
 
-    Ok(TemplateChunk::Expression(InterpolateExpression {
-        left_delim,
-        wants_output,
-        value,
-        right_delim,
-    }))
+    let get_tokens = repeat_till(1.., parse_interpolate_token, peek("}}"));
+    let recover = take_until(0.., "}}").void();
+
+    let (inside_tokens, _): (Vec<_>, _) = get_tokens
+        .resume_after(recover)
+        .with_taken()
+        .map(|(val, taken)| val.unwrap_or_else(|| (vec![TemplateToken::Invalid(taken)], "")))
+        .parse_next(input)?;
+
+    let right_delim = "}}".map(TemplateToken::RightDelim).parse_next(input)?;
+
+    let mut tokens = vec![left_delim];
+    tokens.extend(inside_tokens);
+    tokens.push(right_delim);
+
+    Ok(tokens)
 }
 
-fn parse_value<'input>(input: &mut Input<'input>) -> PResult<'input, TemplateExpression<'input>> {
-    let before_ws = multispace0(input)?;
-
-    let expr = trace("parse_value", alt((parse_variable,))).parse_next(input)?;
-
-    let after_ws = multispace0(input)?;
-
-    Ok(TemplateExpression {
-        before_ws,
-        expr,
-        after_ws,
-    })
+fn parse_interpolate_token<'input>(
+    input: &mut Input<'input>,
+) -> PResult<'input, TemplateToken<'input>> {
+    trace(
+        "parse_interpolate_token",
+        alt((parse_ident, parse_whitespace)),
+    )
+    .parse_next(input)
 }
 
-fn parse_variable<'input>(input: &mut Input<'input>) -> PResult<'input, TemplateExpr<'input>> {
-    terminated(alpha1, ident_terminator_check)
-        .map(TemplateExpr::Variable)
-        .context(ParseError::ctx().msg("valid variables are alpha"))
+fn parse_whitespace<'input>(input: &mut Input<'input>) -> PResult<'input, TemplateToken<'input>> {
+    trace(
+        "parse_whitespace",
+        multispace1.map(TemplateToken::Whitespace),
+    )
+    .parse_next(input)
+}
+
+fn parse_ident<'input>(input: &mut Input<'input>) -> PResult<'input, TemplateToken<'input>> {
+    let ident = ident.map(TemplateToken::Ident).parse_next(input)?;
+
+    ident_terminator_check
+        .context(
+            ParseError::ctx()
+                .msg("Invalid variable identifier")
+                .help("valid variable identifiers are alphanumeric"),
+        )
+        .value(ident)
         .resume_after(bad_ident)
-        .map(|v| v.unwrap_or(TemplateExpr::Variable("BAD_VARIABLE")))
+        .with_taken()
+        .map(|(val, taken)| val.unwrap_or(TemplateToken::Invalid(taken)))
         .parse_next(input)
 }
 
-fn ident_terminator<'input>(input: &mut Input<'input>) -> PResult<'input, ()> {
-    alt((eof.void(), "{".void(), "}".void(), multispace1.void())).parse_next(input)
-}
-
-fn ident_terminator_check<'input>(input: &mut Input<'input>) -> PResult<'input, ()> {
-    cut_err(peek(ident_terminator)).parse_next(input)
+fn ident<'input>(input: &mut Input<'input>) -> PResult<'input, &'input str> {
+    take_while(1.., char::is_alphanumeric).parse_next(input)
 }
 
 fn bad_ident<'input>(input: &mut Input<'input>) -> PResult<'input, ()> {
-    repeat_till(1.., any, peek(ident_terminator))
+    repeat_till(1.., any, ident_terminator_check)
         .map(|((), _)| ())
         .parse_next(input)
 }
 
+fn ident_terminator_check<'input>(input: &mut Input<'input>) -> PResult<'input, ()> {
+    peek(ident_terminator).parse_next(input)
+}
+
+fn ident_terminator<'input>(input: &mut Input<'input>) -> PResult<'input, ()> {
+    alt((
+        eof.void(),
+        one_of(('{', '}')).void(),
+        one_of((' ', '\t', '\r', '\n')).void(),
+    ))
+    .parse_next(input)
+}
+
 #[cfg(test)]
 mod tests {
     use crate::parser::parse;
@@ -292,7 +315,7 @@ mod tests {
         insta::assert_debug_snapshot!(output, @r#"
         Ok(
             ParsedTemplate {
-                content: [
+                tokens: [
                     Content(
                         "Hello There",
                     ),
@@ -310,23 +333,24 @@ mod tests {
         insta::assert_debug_snapshot!(output, @r#"
         Ok(
             ParsedTemplate {
-                content: [
+                tokens: [
                     Content(
                         "Hello ",
                     ),
-                    Expression(
-                        InterpolateExpression {
-                            left_delim: "{{",
-                            wants_output: None,
-                            value: TemplateExpression {
-                                before_ws: " ",
-                                expr: Variable(
-                                    "there",
-                                ),
-                                after_ws: " ",
-                            },
-                            right_delim: "}}",
-                        },
+                    LeftDelim(
+                        "{{",
+                    ),
+                    Whitespace(
+                        " ",
+                    ),
+                    Ident(
+                        "there",
+                    ),
+                    Whitespace(
+                        " ",
+                    ),
+                    RightDelim(
+                        "}}",
                     ),
                 ],
             },
@@ -336,24 +360,27 @@ mod tests {
 
     #[test]
     fn parse_interpolate_bad() {
-        let input = "Hello {{ the2re }}";
+        let input = "Hello {{ the2re }} {{ the@re }}";
         let output = parse(input);
 
         insta::assert_debug_snapshot!(output, @r#"
         Err(
             ParseFailure {
-                source: "Hello {{ the2re }}",
+                source: "Hello {{ the2re }} {{ the@re }}",
                 errors: [
                     ParseError {
                         message: Some(
-                            "valid variables are alpha",
+                            "Invalid variable identifier",
+                        ),
+                        help: Some(
+                            "valid variable identifiers are alphanumeric",
                         ),
                         span: Some(
                             SourceSpan {
-                                range: 9..15,
+                                range: 25..28,
                             },
                         ),
-                        is_fatal: true,
+                        is_fatal: false,
                     },
                 ],
             },

src/parser/snapshots/temple__parser__tests__parse_interpolate_bad-2.snap

@@ -2,7 +2,9 @@
 source: src/parser/mod.rs
 expression: error.to_report()
 ---
-error: valid variables are alpha
+error: Invalid variable identifier
   ╭▸ 
-1 │ Hello {{ the2re }}
-  ╰╴         ━━━━━━
+1 │ Hello {{ the2re }} {{ the@re }}
+  │                          ━━━
+  │
+  ╰ help: valid variable identifiers are alphanumeric