Implement std::error::Error for cocoon::Error via optional thiserror (

#28)

This adds the `std::error::Error` trait implementation to
`cocoon::Error` using the `thiserror` crate.
Note that this is only limited to the presence of feature "thiserror".

Co-authored-by: Alexander Fadeev <[email protected]>
Co-authored-by: madomado <[email protected]>

Cargo.toml

@@ -20,6 +20,7 @@ hmac = "0.11"
 pbkdf2 = {version = "0.9", default-features = false, features = ["sha2", "hmac"]}
 rand = {version = "0.8", default-features = false, features = ["std_rng"]}
 sha2 = {version = "0.9", default-features = false}
+thiserror = {version = "1.0.61", optional = true}
 zeroize = {version = "1", default-features = false}
 
 [dev-dependencies]

src/error.rs

@@ -1,20 +1,39 @@
 /// Error variants produced by the Cocoon API.
 #[derive(Debug)]
+#[cfg_attr(feature = "thiserror", derive(thiserror::Error))]
 pub enum Error {
     /// I/o error during read/write operation (`Cocoon::dump`, `Cocoon::parse`).
     #[cfg(feature = "std")]
+    #[cfg_attr(feature = "thiserror", error("Input/output error"))]
     Io(std::io::Error),
+
     /// Format is not recognized. Probably corrupted.
+    #[cfg_attr(feature = "thiserror", error("Unrecognized format"))]
     UnrecognizedFormat,
+
     /// Cryptographic error. There could be a few reasons:
     /// 1. Integrity is compromised.
     /// 2. Password is invalid.
+    #[cfg_attr(
+        feature = "thiserror",
+        error("Cryptographic error: bad integrity/password")
+    )]
     Cryptography,
+
     /// Container is too large to get processed on the current architecture.
     /// E.g. it's not possible to process a container larger than 4 GB on 32-bit architecture.
+    #[cfg_attr(
+        feature = "thiserror",
+        error("Container size exceeds architectural limit")
+    )]
     TooLarge,
+
     /// Buffer is too short and barely holds all data to decrypt, inconsistent length
     /// encoded to the header.
+    #[cfg_attr(
+        feature = "thiserror",
+        error("Insufficient buffer size for decrypted data")
+    )]
     TooShort,
 }