improve error message

src/parser/tokenizer.rs

@@ -1,4 +1,3 @@
-use std::io::Write;
 use std::result::Result;
 
 use super::path_reader::{PathReader, ReaderError};
@@ -368,13 +367,7 @@ impl<'a> TokenReader<'a> {
     }
 
     pub fn err_msg_with_pos(&self, pos: usize) -> String {
-        let mut w = Vec::new();
-        writeln!(&mut w, "{}", self.origin_input).unwrap();
-        writeln!(&mut w, "{}", "^".repeat(pos)).unwrap();
-        match std::str::from_utf8(&w[..]) {
-            Ok(s) => s.to_owned(),
-            Err(_) => panic!("Invalid UTF-8"),
-        }
+        format!("{}\n{}", self.origin_input, "^".repeat(pos))
     }
 
     pub fn err_msg(&self) -> String {

src/select/mod.rs

@@ -1,4 +1,5 @@
 use std::collections::HashSet;
+use std::fmt;
 
 use array_tool::vec::{Intersect, Union};
 use indexmap::IndexMap;
@@ -514,7 +515,6 @@ enum FilterKey {
     All,
 }
 
-#[derive(Debug)]
 pub enum JsonPathError {
     EmptyPath,
     EmptyValue,
@@ -522,6 +522,23 @@ pub enum JsonPathError {
     Serde(String),
 }
 
+impl fmt::Debug for JsonPathError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", self)
+    }
+}
+
+impl fmt::Display for JsonPathError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            JsonPathError::EmptyPath => f.write_str("path not set"),
+            JsonPathError::EmptyValue => f.write_str("json value not set"),
+            JsonPathError::Path(msg) => f.write_str(&format!("path error: \n{}\n", msg)),
+            JsonPathError::Serde(msg) => f.write_str(&format!("serde error: \n{}\n", msg)),
+        }
+    }
+}
+
 #[derive(Debug)]
 pub struct Selector<'a, 'b> {
     node: Option<Node>,