Return error instead of panic on failed parse

Cargo.lock

@@ -46,10 +46,11 @@ dependencies = [
 
 [[package]]
 name = "blueprint"
-version = "0.2.0"
+version = "0.3.0"
 dependencies = [
  "nom",
  "structopt",
+ "thiserror",
 ]
 
 [[package]]
@@ -257,6 +258,26 @@ dependencies = [
  "unicode-width",
 ]
 
+[[package]]
+name = "thiserror"
+version = "1.0.24"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e0f4a65597094d4483ddaed134f409b2cb7c1beccf25201a9f73c719254fa98e"
+dependencies = [
+ "thiserror-impl",
+]
+
+[[package]]
+name = "thiserror-impl"
+version = "1.0.24"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7765189610d8241a44529806d6fd1f2e0a08734313a35d5b3a556f92b381f3c0"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "unicode-segmentation"
 version = "1.7.1"

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "blueprint"
-version = "0.2.0"
+version = "0.3.0"
 authors = ["Joakim Hulthe <joakim@hulthe.net>"]
 description = "A simple templating library"
 edition = "2018"
@@ -9,3 +9,4 @@ edition = "2018"
 [dependencies]
 nom = "6.1.2"
 structopt = "0.3.21"
+thiserror = "1.0.24"

src/error.rs

@@ -0,0 +1,7 @@
+use thiserror::Error;
+
+#[derive(Debug, Error)]
+pub enum Error {
+    #[error("Failed to parse template")]
+    ParseError,
+}

src/lib.rs

@@ -1,10 +1,12 @@
 mod ast;
 mod env;
+mod error;
 mod parser;
 
 pub use ast::{CmpOp, Expr, IfThen, Part, Template};
 pub use env::{Env, Value};
-pub use parser::parse_file;
+pub use error::Error;
+pub use parser::parse_template;
 
 #[cfg(test)]
 mod test {
@@ -13,7 +15,7 @@ mod test {
     #[test]
     fn test_parse_empty() {
         let input = "";
-        let ast = parse_file(&input).expect("failed to parse");
+        let ast = parse_template(&input).expect("failed to parse");
         eprintln!("{:#?}", ast);
         assert_eq!(ast, Template { parts: vec![] });
     }
@@ -21,7 +23,7 @@ mod test {
     #[test]
     fn test_parse_text() {
         let input = "hello there    GENERAL KENOBI";
-        let ast = parse_file(&input).expect("failed to parse");
+        let ast = parse_template(&input).expect("failed to parse");
         eprintln!("{:#?}", ast);
         assert_eq!(
             ast,
@@ -34,7 +36,7 @@ mod test {
     #[test]
     fn test_parse_if() {
         let input = "one {% if foo %} two {% end %} three";
-        let ast = parse_file(&input).expect("failed to parse");
+        let ast = parse_template(&input).expect("failed to parse");
         eprintln!("{:#?}", ast);
         assert_eq!(
             ast,
@@ -58,7 +60,7 @@ mod test {
     #[test]
     fn test_parse_if_str() {
         let input = "one {% if foo >= \"bar\" %} two {% end %} three";
-        let ast = parse_file(&input).expect("failed to parse");
+        let ast = parse_template(&input).expect("failed to parse");
         eprintln!("{:#?}", ast);
         assert_eq!(
             ast,
@@ -86,7 +88,7 @@ mod test {
     #[test]
     fn test_parse_eq() {
         let input = "one {% if foo == bar %} two {% end %} three";
-        let ast = parse_file(&input).expect("failed to parse");
+        let ast = parse_template(&input).expect("failed to parse");
         eprintln!("{:#?}", ast);
         assert_eq!(
             ast,
@@ -114,7 +116,7 @@ mod test {
     #[test]
     fn test_parse_if_elif_else() {
         let input = "one {% if foo %} two {% elif bar %} three {% else %} four {% end %} five";
-        let ast = parse_file(&input).expect("failed to parse");
+        let ast = parse_template(&input).expect("failed to parse");
         eprintln!("{:#?}", ast);
         assert_eq!(
             ast,
@@ -141,7 +143,7 @@ mod test {
     #[test]
     fn test_parse_nested() {
         let input = "one {% if foo %} two {% if bar %} three {% end %} four {% end %} five";
-        let ast = parse_file(&input).expect("failed to parse");
+        let ast = parse_template(&input).expect("failed to parse");
         eprintln!("{:#?}", ast);
         let expected = Template {
             parts: vec![

src/main.rs

@@ -13,11 +13,11 @@ struct Opt {
 fn main() {
     let opt = Opt::from_args();
     let file = read_to_string(&opt.template).expect("failed to load file");
-    let template = blueprint::parse_file(&file).expect("failed to parse");
+    let template = blueprint::parse_template(&file).expect("failed to parse");
     let env = opt
         .env
         .into_iter()
-        .map(|key| (key, Value::Str("".into())))
+        .map(|key| (key, Value::Bool(true)))
         .collect();
 
     let mut stdout = io::stdout();

src/parser.rs

@@ -1,4 +1,5 @@
-use crate::ast::*;
+use crate::ast::{CmpOp, Expr, IfThen, Part, Template};
+use crate::Error;
 use nom::{
     branch::alt,
     bytes::complete::{is_not, tag, take_until},
@@ -162,19 +163,21 @@ fn block(word: &'static str) -> impl Fn(&str) -> IResult<&str, ()> {
     }
 }
 
-pub fn parse_file(file: &str) -> Result<Template, ()> {
+pub fn parse_template(template: &str) -> Result<Template, Error> {
-    match parts(file) {
+    match parts(template) {
         Ok((rest, parts)) => {
             //eprintln!("{:#?}", parts);
 
             if rest != "" {
-                panic!("failed to parse input. remainder: \"{}\"", rest);
+                //panic!("failed to parse input. remainder: \"{}\"", rest);
+                Err(Error::ParseError)
+            } else {
+                Ok(Template { parts })
             }
-
-            Ok(Template { parts })
         }
-        Err(e) => {
+        Err(_e) => {
-            panic!("{:#?}", e);
+            //panic!("{:#?}", _e);
+            Err(Error::ParseError)
         }
     }
 }