derive: define separate ParseError type

4 files changed, 32 insertions, 9 deletions

diff --git a/askama_derive/src/generator.rs b/askama_derive/src/generator.rs
index f8b9ecb..f17b6f6 100644
--- a/askama_derive/src/generator.rs
+++ b/askama_derive/src/generator.rs
@@ -259,7 +259,11 @@ mod _parsed {
             // internally we will transmute it to `&'static str` to satisfy the compiler.
             // However, we only expose the nodes with a lifetime limited to `self`.
             let src = unsafe { mem::transmute::<&str, &'static str>(source.as_str()) };
-            let nodes = parse(src, syntax)?;
+            let nodes = match parse(src, syntax) {
+                Ok(nodes) => nodes,
+                Err(e) => return Err(e.to_string().into()),
+            };
+
             Ok(Self { source, nodes })
         }
 
diff --git a/askama_derive/src/lib.rs b/askama_derive/src/lib.rs
index 0683e71..1483438 100644
--- a/askama_derive/src/lib.rs
+++ b/askama_derive/src/lib.rs
@@ -12,6 +12,7 @@ mod generator;
 mod heritage;
 mod input;
 mod parser;
+use parser::ParseError;
 
 #[proc_macro_derive(Template, attributes(template))]
 pub fn derive_template(input: TokenStream) -> TokenStream {
@@ -48,6 +49,13 @@ impl fmt::Display for CompileError {
     }
 }
 
+impl From<ParseError> for CompileError {
+    #[inline]
+    fn from(e: ParseError) -> Self {
+        Self::new(e.to_string(), Span::call_site())
+    }
+}
+
 impl From<&'static str> for CompileError {
     #[inline]
     fn from(s: &'static str) -> Self {
diff --git a/askama_derive/src/parser/mod.rs b/askama_derive/src/parser/mod.rs
index f81bcc8..0bf68ca 100644
--- a/askama_derive/src/parser/mod.rs
+++ b/askama_derive/src/parser/mod.rs
@@ -1,5 +1,5 @@
 use std::cell::Cell;
-use std::str;
+use std::{fmt, str};
 
 use nom::branch::alt;
 use nom::bytes::complete::{escaped, is_not, tag, take_till};
@@ -13,7 +13,6 @@ use nom::{error_position, AsChar, IResult, InputTakeAtPosition};
 
 pub(crate) use self::expr::Expr;
 pub(crate) use self::node::{Cond, CondTest, Loop, Macro, Node, Target, When, Whitespace, Ws};
-use crate::CompileError;
 
 mod expr;
 mod node;
@@ -57,11 +56,11 @@ impl From<char> for Whitespace {
     }
 }
 
-pub(crate) fn parse<'a>(src: &'a str, syntax: &Syntax<'_>) -> Result<Vec<Node<'a>>, CompileError> {
+pub(crate) fn parse<'a>(src: &'a str, syntax: &Syntax<'_>) -> Result<Vec<Node<'a>>, ParseError> {
     match Node::parse(src, &State::new(syntax)) {
         Ok((left, res)) => {
             if !left.is_empty() {
-                Err(format!("unable to parse template:\n\n{left:?}").into())
+                Err(ParseError(format!("unable to parse template:\n\n{left:?}")))
             } else {
                 Ok(res)
             }
@@ -86,10 +85,22 @@ pub(crate) fn parse<'a>(src: &'a str, syntax: &Syntax<'_>) -> Result<Vec<Node<'a
                 column,
                 source_after,
             );
-            Err(msg.into())
+
+            Err(ParseError(msg))
         }
 
-        Err(nom::Err::Incomplete(_)) => Err("parsing incomplete".into()),
+        Err(nom::Err::Incomplete(_)) => Err(ParseError("parsing incomplete".into())),
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub(crate) struct ParseError(String);
+
+impl std::error::Error for ParseError {}
+
+impl fmt::Display for ParseError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.0.fmt(f)
     }
 }
 
diff --git a/askama_derive/src/parser/tests.rs b/askama_derive/src/parser/tests.rs
index 68cf14b..0e785eb 100644
--- a/askama_derive/src/parser/tests.rs
+++ b/askama_derive/src/parser/tests.rs
@@ -260,7 +260,7 @@ fn test_rust_macro() {
     assert_eq!(
         &*super::parse("{{a.b.c!( hello )}}", &syntax)
             .unwrap_err()
-            .msg,
+            .to_string(),
         "problems parsing template source at row 1, column 7 near:\n\"!( hello )}}\"",
     );
 }
@@ -706,7 +706,7 @@ fn test_missing_space_after_kw() {
     let syntax = Syntax::default();
     let err = super::parse("{%leta=b%}", &syntax).unwrap_err();
     assert!(matches!(
-        &*err.msg,
+        &*err.to_string(),
         "unable to parse template:\n\n\"{%leta=b%}\""
     ));
 }