Refactor ParseError

Instead of the `crate::Error`, the <private> method `stream::parse_headers`
will return the specialized error with kind enumerating the possible
causes of parsing errors. This change will help to specialize errors
error returned by public methods.

Along this change, I also refactored 2 errors, namely
the `ParseHeaderNameError` and the `ParseHeaderValueError`
to convert them to specialization of generic `crate::error::Error<_>`.

These changes are collected in the same commit because all of them
describe errors occurred during either building or parsing headers.

async-nats/src/error.rs

@@ -73,7 +73,7 @@ where
 
 /// Enables wrapping source errors to the crate-specific error type
 /// by additionally specifying the kind of the target error.
-trait WithKind<Kind>
+pub(crate) trait WithKind<Kind>
 where
     Kind: Clone + Debug + Display + PartialEq,
     Self: Into<crate::Error>,

async-nats/src/header.rs

@@ -22,6 +22,7 @@
 
 use std::{collections::HashMap, fmt, slice::Iter, str::FromStr};
 
+use crate::error::Error;
 use bytes::Bytes;
 use serde::{Deserialize, Serialize};
 
@@ -312,7 +313,7 @@ impl FromStr for HeaderValue {
 
     fn from_str(s: &str) -> Result<Self, Self::Err> {
         if s.contains(['\r', '\n']) {
-            return Err(ParseHeaderValueError);
+            return Err(s.into());
         }
 
         Ok(HeaderValue {
@@ -339,19 +340,26 @@ impl HeaderValue {
     }
 }
 
-#[derive(Debug, Clone)]
-pub struct ParseHeaderValueError;
+#[derive(Clone, Debug, PartialEq)]
+pub struct ParseHeaderValueErrorKind(String);
 
-impl fmt::Display for ParseHeaderValueError {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+impl fmt::Display for ParseHeaderValueErrorKind {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(
             f,
-            r#"invalid character found in header value (value cannot contain '\r' or '\n')"#
+            r#"invalid character found in header value (value cannot contain '\r' or '\n'): {:?}"#,
+            self.0
         )
     }
 }
 
-impl std::error::Error for ParseHeaderValueError {}
+pub type ParseHeaderValueError = Error<ParseHeaderValueErrorKind>;
+
+impl From<&str> for ParseHeaderValueError {
+    fn from(value: &str) -> Self {
+        Self::new(ParseHeaderValueErrorKind(value.into()))
+    }
+}
 
 pub trait IntoHeaderName {
     fn into_header_name(self) -> HeaderName;
@@ -568,7 +576,9 @@ impl FromStr for HeaderName {
 
     fn from_str(s: &str) -> Result<Self, Self::Err> {
         if s.contains(|c: char| c == ':' || (c as u8) < 33 || (c as u8) > 126) {
-            return Err(ParseHeaderNameError);
+            return Err(ParseHeaderNameError::new(ParseHeaderNameErrorKind(
+                s.into(),
+            )));
         }
 
         match StandardHeader::from_bytes(s.as_ref()) {
@@ -600,16 +610,22 @@ impl AsRef<str> for HeaderName {
     }
 }
 
-#[derive(Debug, Clone)]
-pub struct ParseHeaderNameError;
+#[derive(Clone, Debug, PartialEq)]
+pub struct ParseHeaderNameErrorKind(String);
 
-impl std::fmt::Display for ParseHeaderNameError {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "invalid header name (name cannot contain non-ascii alphanumeric characters other than '-')")
+impl fmt::Display for ParseHeaderNameErrorKind {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "invalid header name (name cannot contain non-ascii alphanumeric characters other than '-'): {:?}", self.0)
     }
 }
 
-impl std::error::Error for ParseHeaderNameError {}
+pub type ParseHeaderNameError = Error<ParseHeaderNameErrorKind>;
+
+impl From<&str> for ParseHeaderNameError {
+    fn from(value: &str) -> Self {
+        Self::new(ParseHeaderNameErrorKind(value.into()))
+    }
+}
 
 #[cfg(test)]
 mod tests {

async-nats/src/jetstream/stream.rs

@@ -15,10 +15,11 @@
 
 #[cfg(feature = "server_2_10")]
 use std::collections::HashMap;
+use std::fmt::Formatter;
 use std::{
     fmt::{self, Debug, Display},
     future::IntoFuture,
-    io::{self, ErrorKind},
+    io::ErrorKind,
     pin::Pin,
     str::FromStr,
     task::Poll,
@@ -1311,31 +1312,64 @@ fn is_continuation(c: char) -> bool {
 }
 const HEADER_LINE: &str = "NATS/1.0";
 
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub enum ParseHeadersErrorKind {
+    HeaderInfoMissing,
+    InvalidHeader,
+    InvalidVersionLine,
+    InvalidStatusCode,
+    MalformedHeader,
+}
+
+impl Display for ParseHeadersErrorKind {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::InvalidHeader => write!(f, "invalid header"),
+            Self::InvalidStatusCode => write!(f, "invalid status code"),
+            Self::InvalidVersionLine => write!(f, "version line does not start with NATS/1.0"),
+            Self::HeaderInfoMissing => write!(f, "expected header information not found"),
+            Self::MalformedHeader => write!(f, "malformed header line"),
+        }
+    }
+}
+
+pub type ParseHeadersError = Error<ParseHeadersErrorKind>;
+
+impl From<ParseHeaderNameError> for ParseHeadersError {
+    fn from(e: ParseHeaderNameError) -> Self {
+        e.with_kind(ParseHeadersErrorKind::MalformedHeader)
+    }
+}
+
+impl From<ParseHeaderValueError> for ParseHeadersError {
+    fn from(e: ParseHeaderValueError) -> Self {
+        e.with_kind(ParseHeadersErrorKind::MalformedHeader)
+    }
+}
+
+impl From<InvalidStatusCode> for ParseHeadersError {
+    fn from(e: InvalidStatusCode) -> Self {
+        e.with_kind(ParseHeadersErrorKind::InvalidStatusCode)
+    }
+}
+
 #[allow(clippy::type_complexity)]
 fn parse_headers(
     buf: &[u8],
-) -> Result<(Option<HeaderMap>, Option<StatusCode>, Option<String>), crate::Error> {
+) -> Result<(Option<HeaderMap>, Option<StatusCode>, Option<String>), ParseHeadersError> {
     let mut headers = HeaderMap::new();
     let mut maybe_status: Option<StatusCode> = None;
     let mut maybe_description: Option<String> = None;
     let mut lines = if let Ok(line) = std::str::from_utf8(buf) {
         line.lines().peekable()
     } else {
-        return Err(Box::new(std::io::Error::new(
-            ErrorKind::Other,
-            "invalid header",
-        )));
+        return Err(ParseHeadersErrorKind::InvalidHeader.into());
     };
 
     if let Some(line) = lines.next() {
         let line = line
             .strip_prefix(HEADER_LINE)
-            .ok_or_else(|| {
-                Box::new(std::io::Error::new(
-                    ErrorKind::Other,
-                    "version line does not start with NATS/1.0",
-                ))
-            })?
+            .ok_or_else(|| ParseHeadersError::new(ParseHeadersErrorKind::InvalidHeader))?
             .trim();
 
         match line.split_once(' ') {
@@ -1355,10 +1389,7 @@ fn parse_headers(
             }
         }
     } else {
-        return Err(Box::new(std::io::Error::new(
-            ErrorKind::Other,
-            "expected header information not found",
-        )));
+        return Err(ParseHeadersErrorKind::HeaderInfoMissing.into());
     };
 
     while let Some(line) = lines.next() {
@@ -1373,16 +1404,9 @@ fn parse_headers(
                 s.push_str(v.trim());
             }
 
-            headers.insert(
-                HeaderName::from_str(k)?,
-                HeaderValue::from_str(&s)
-                    .map_err(|err| Box::new(io::Error::new(ErrorKind::Other, err)))?,
-            );
+            headers.insert(HeaderName::from_str(k)?, HeaderValue::from_str(&s)?);
         } else {
-            return Err(Box::new(std::io::Error::new(
-                ErrorKind::Other,
-                "malformed header line",
-            )));
+            return Err(ParseHeadersErrorKind::MalformedHeader.into());
         }
     }
 
@@ -1528,6 +1552,9 @@ pub struct External {
     pub delivery_prefix: Option<String>,
 }
 
+use crate::error::WithKind;
+use crate::header::{ParseHeaderNameError, ParseHeaderValueError};
+use crate::status::InvalidStatusCode;
 use std::marker::PhantomData;
 
 #[derive(Debug, Default)]