error: simplify error implementation

Use thiserror for handy from and display macros

Cargo.toml

@@ -20,6 +20,7 @@ bindgen = []
 [dependencies]
 flatbuffers = "23.5.26"
 libc = "0.2.151"
+thiserror = "2.0.3"
 tokio = { version = "1", features = ["rt-multi-thread", "macros"] }
 tracing = "0.1.40"
 tracing-subscriber = "0.3.18"

src/error.rs

@@ -1,27 +1,46 @@
-use std::fmt;
+use thiserror::Error;
 
-#[derive(Debug, Eq, PartialEq)]
+/// Main error type
+#[derive(Debug, Error)]
 pub enum Error {
+    #[error("Database open failed")]
     DbOpenFailed,
+
+    #[error("Not found")]
     NotFound,
+
+    #[error("Decode error")]
     DecodeError,
+
+    #[error("Query failed")]
     QueryError,
+
+    #[error("Note process failed")]
     NoteProcessFailed,
+
+    #[error("Transaction failed")]
     TransactionFailed,
+
+    #[error("Subscription failed")]
     SubscriptionError,
+
+    #[error("Buffer overflow")]
     BufferOverflow,
-    Filter(FilterError),
-}
 
-impl Error {
-    pub fn filter(ferr: FilterError) -> Self {
-        Error::Filter(ferr)
-    }
+    #[error("Filter error: {0}")]
+    Filter(#[from] FilterError),
+
+    #[error("IO error: {0}")]
+    IO(#[from] std::io::Error),
 }
 
-#[derive(Debug, Eq, PartialEq)]
+/// Filter-specific error type
+#[derive(Debug, Error, Eq, PartialEq)]
 pub enum FilterError {
+    #[error("Field already exists")]
     FieldAlreadyExists,
+
+    #[error("Field already started")]
     FieldAlreadyStarted,
 }
 
@@ -34,30 +53,3 @@ impl FilterError {
         Error::Filter(FilterError::FieldAlreadyStarted)
     }
 }
-
-impl fmt::Display for FilterError {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self {
-            FilterError::FieldAlreadyExists => write!(f, "field already exists"),
-            FilterError::FieldAlreadyStarted => write!(f, "field already started"),
-        }
-    }
-}
-
-impl fmt::Display for Error {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self {
-            Error::DbOpenFailed => write!(f, "Open failed"),
-            Error::NotFound => write!(f, "Not found"),
-            Error::QueryError => write!(f, "Query failed"),
-            Error::DecodeError => write!(f, "Decode error"),
-            Error::NoteProcessFailed => write!(f, "Note process failed"),
-            Error::TransactionFailed => write!(f, "Transaction failed"),
-            Error::SubscriptionError => write!(f, "Subscription failed"),
-            Error::BufferOverflow => write!(f, "Buffer overflow"),
-            Error::Filter(filter_err) => write!(f, "Filter: {filter_err}"),
-        }
-    }
-}
-
-impl std::error::Error for Error {}

src/filter.rs

@@ -401,7 +401,7 @@ impl FilterBuilder {
         let r =
             unsafe { bindings::ndb_filter_start_tag_field(self.as_mut_ptr(), tag as u8 as c_char) };
         if r == 0 {
-            return Err(Error::filter(FilterError::FieldAlreadyStarted));
+            return Err(FilterError::FieldAlreadyStarted.into());
         }
         Ok(())
     }

src/note.rs

@@ -509,7 +509,7 @@ mod tests {
             let err = ndb
                 .get_note_by_id(&mut txn, &[0; 32])
                 .expect_err("not found");
-            assert!(err == Error::NotFound);
+            assert!(matches!(err, Error::NotFound));
         }
 
         test_util::cleanup_db(db);

src/transaction.rs

@@ -69,7 +69,7 @@ mod tests {
             {
                 let _txn = Transaction::new(&ndb).expect("txn1 failed");
                 let txn2 = Transaction::new(&ndb).expect_err("tx2");
-                assert!(txn2 == Error::TransactionFailed);
+                assert!(matches!(txn2, Error::TransactionFailed));
             }
 
             {