Hide all errors

Hide the internals of all errors by wrapping enum variant internals in
structs.

Author: tcharding

examples/custom.rs

@@ -117,7 +117,7 @@ impl<'a> fmt::UpperHex for DisplayALittleBitHexy<'a> {
 }
 
 /// Example Error.
-#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq)]
 pub enum Error {
     /// Conversion error while parsing hex string.
     Conversion(HexToBytesError),

src/error.rs

@@ -2,6 +2,8 @@
 
 use core::fmt;
 
+use crate::write_err;
+
 /// Formats error.
 ///
 /// If `std` feature is OFF appends error source (delimited by `: `). We do this because
@@ -28,18 +30,19 @@ macro_rules! write_err {
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
 pub enum HexToBytesError {
     /// Non-hexadecimal character.
-    InvalidChar(u8),
+    InvalidChar(InvalidCharError),
     /// Purported hex string had odd length.
-    OddLengthString(usize),
+    OddLengthString(OddLengthStringError),
 }
 
 impl fmt::Display for HexToBytesError {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         use HexToBytesError::*;
 
         match *self {
-            InvalidChar(ch) => write!(f, "invalid hex character {}", ch),
-            OddLengthString(ell) => write!(f, "odd hex string length {}", ell),
+            InvalidChar(ref e) => write_err!(f, "invalid char, failed to create bytes from hex"; e),
+            OddLengthString(ref e) =>
+                write_err!(f, "odd length, failed to create bytes from hex"; e),
         }
     }
 }
@@ -49,29 +52,75 @@ impl std::error::Error for HexToBytesError {
     fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
         use HexToBytesError::*;
 
-        match self {
-            InvalidChar(_) | OddLengthString(_) => None,
+        match *self {
+            InvalidChar(ref e) => Some(e),
+            OddLengthString(ref e) => Some(e),
         }
     }
 }
 
-/// Hex decoding error.
+impl From<InvalidCharError> for HexToBytesError {
+    #[inline]
+    fn from(e: InvalidCharError) -> Self { Self::InvalidChar(e) }
+}
+
+impl From<OddLengthStringError> for HexToBytesError {
+    #[inline]
+    fn from(e: OddLengthStringError) -> Self { Self::OddLengthString(e) }
+}
+
+/// Invalid hex character.
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub struct InvalidCharError {
+    pub(crate) invalid: u8,
+}
+
+impl fmt::Display for InvalidCharError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "invalid hex char {}", self.invalid)
+    }
+}
+
+#[cfg(feature = "std")]
+impl std::error::Error for InvalidCharError {
+    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> { None }
+}
+
+/// Purported hex string had odd length.
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
+pub struct OddLengthStringError {
+    pub(crate) len: usize,
+}
+
+impl fmt::Display for OddLengthStringError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "odd hex string length {}", self.len)
+    }
+}
+
+#[cfg(feature = "std")]
+impl std::error::Error for OddLengthStringError {
+    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> { None }
+}
+
+/// Hex decoding error.
+#[derive(Debug, Clone, PartialEq, Eq)]
 pub enum HexToArrayError {
     /// Conversion error while parsing hex string.
     Conversion(HexToBytesError),
     /// Tried to parse fixed-length hash from a string with the wrong length (got, want).
-    InvalidLength(usize, usize),
+    InvalidLength(InvalidLengthError),
 }
 
 impl fmt::Display for HexToArrayError {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         use HexToArrayError::*;
 
         match *self {
-            Conversion(ref e) => crate::write_err!(f, "conversion error"; e),
-            InvalidLength(got, want) =>
-                write!(f, "bad hex string length {} (expected {})", got, want),
+            Conversion(ref e) =>
+                crate::write_err!(f, "conversion error, failed to create array from hex"; e),
+            InvalidLength(ref e) =>
+                write_err!(f, "invalid length, failed to create array from hex"; e),
         }
     }
 }
@@ -83,7 +132,7 @@ impl std::error::Error for HexToArrayError {
 
         match *self {
             Conversion(ref e) => Some(e),
-            InvalidLength(_, _) => None,
+            InvalidLength(ref e) => Some(e),
         }
     }
 }
@@ -92,3 +141,26 @@ impl From<HexToBytesError> for HexToArrayError {
     #[inline]
     fn from(e: HexToBytesError) -> Self { Self::Conversion(e) }
 }
+
+impl From<InvalidLengthError> for HexToArrayError {
+    #[inline]
+    fn from(e: InvalidLengthError) -> Self { Self::InvalidLength(e) }
+}
+
+/// Tried to parse fixed-length hash from a string with the wrong length.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct InvalidLengthError {
+    pub(crate) expected: usize,
+    pub(crate) got: usize,
+}
+
+impl fmt::Display for InvalidLengthError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "bad hex string length {} (expected {})", self.got, self.expected)
+    }
+}
+
+#[cfg(feature = "std")]
+impl std::error::Error for InvalidLengthError {
+    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> { None }
+}

src/iter.rs

@@ -10,7 +10,8 @@ use std::io;
 #[cfg(all(feature = "core2", not(feature = "std")))]
 use core2::io;
 
-use crate::parse::HexToBytesError;
+#[rustfmt::skip]                // Keep public re-exports separate.
+pub use crate::error::{HexToBytesError, OddLengthStringError, InvalidCharError};
 
 /// Iterator over a hex-encoded string slice which decodes hex and yields bytes.
 pub struct HexToBytesIter<'a> {
@@ -33,7 +34,7 @@ impl<'a> HexToBytesIter<'a> {
     #[inline]
     pub fn new(s: &'a str) -> Result<HexToBytesIter<'a>, HexToBytesError> {
         if s.len() % 2 != 0 {
-            Err(HexToBytesError::OddLengthString(s.len()))
+            Err(HexToBytesError::OddLengthString(OddLengthStringError { len: s.len() }))
         } else {
             Ok(HexToBytesIter { iter: s.bytes() })
         }
@@ -93,8 +94,12 @@ impl<'a> io::Read for HexToBytesIter<'a> {
 
 /// `hi` and `lo` are bytes representing hex characters.
 fn hex_chars_to_byte(hi: u8, lo: u8) -> Result<u8, HexToBytesError> {
-    let hih = (hi as char).to_digit(16).ok_or(HexToBytesError::InvalidChar(hi))?;
-    let loh = (lo as char).to_digit(16).ok_or(HexToBytesError::InvalidChar(lo))?;
+    let hih = (hi as char)
+        .to_digit(16)
+        .ok_or(HexToBytesError::InvalidChar(InvalidCharError { invalid: hi }))?;
+    let loh = (lo as char)
+        .to_digit(16)
+        .ok_or(HexToBytesError::InvalidChar(InvalidCharError { invalid: lo }))?;
 
     let ret = (hih << 4) + loh;
     Ok(ret as u8)

src/parse.rs

@@ -9,7 +9,7 @@ use crate::alloc::vec::Vec;
 use crate::iter::HexToBytesIter;
 
 #[rustfmt::skip]                // Keep public re-exports separate.
-pub use crate::error::{HexToBytesError, HexToArrayError};
+pub use crate::error::{HexToBytesError, HexToArrayError, InvalidLengthError, OddLengthStringError, InvalidCharError};
 
 /// Trait for objects that can be deserialized from hex strings.
 pub trait FromHex: Sized {
@@ -58,7 +58,10 @@ macro_rules! impl_fromhex_array {
                     }
                     Ok(ret)
                 } else {
-                    Err(HexToArrayError::InvalidLength(2 * $len, 2 * iter.len()))
+                    Err(HexToArrayError::InvalidLength(InvalidLengthError {
+                        expected: 2 * $len,
+                        got: 2 * iter.len(),
+                    }))
                 }
             }
         }
@@ -93,21 +96,28 @@ mod tests {
     #[test]
     #[cfg(feature = "alloc")]
     fn hex_error() {
-        use HexToBytesError::*;
-
         let oddlen = "0123456789abcdef0";
         let badchar1 = "Z123456789abcdef";
         let badchar2 = "012Y456789abcdeb";
         let badchar3 = "«23456789abcdef";
 
-        assert_eq!(Vec::<u8>::from_hex(oddlen), Err(OddLengthString(17)));
+        assert_eq!(Vec::<u8>::from_hex(oddlen), Err(OddLengthStringError { len: 17 }.into()));
         assert_eq!(
             <[u8; 4]>::from_hex(oddlen),
-            Err(HexToArrayError::Conversion(OddLengthString(17)))
+            Err(HexToBytesError::OddLengthString(OddLengthStringError { len: 17 }).into())
+        );
+        assert_eq!(
+            Vec::<u8>::from_hex(badchar1),
+            Err(HexToBytesError::InvalidChar(InvalidCharError { invalid: b'Z' }).into())
+        );
+        assert_eq!(
+            Vec::<u8>::from_hex(badchar2),
+            Err(HexToBytesError::InvalidChar(InvalidCharError { invalid: b'Y' }).into())
+        );
+        assert_eq!(
+            Vec::<u8>::from_hex(badchar3),
+            Err(HexToBytesError::InvalidChar(InvalidCharError { invalid: 194 }).into())
         );
-        assert_eq!(Vec::<u8>::from_hex(badchar1), Err(InvalidChar(b'Z')));
-        assert_eq!(Vec::<u8>::from_hex(badchar2), Err(InvalidChar(b'Y')));
-        assert_eq!(Vec::<u8>::from_hex(badchar3), Err(InvalidChar(194)));
     }
 
     #[test]
@@ -117,9 +127,11 @@ mod tests {
     }
     #[test]
     fn hex_to_array_error() {
-        use HexToArrayError::*;
         let len_sixteen = "0123456789abcdef";
-        assert_eq!(<[u8; 4]>::from_hex(len_sixteen), Err(InvalidLength(8, 16)));
+        assert_eq!(
+            <[u8; 4]>::from_hex(len_sixteen),
+            Err(InvalidLengthError { expected: 8, got: 16 }.into())
+        )
     }
 
     #[test]