transaction: use proper 'ParseError' type

Cargo.lock

@@ -296,6 +296,7 @@ dependencies = [
  "fpdec",
  "serde",
  "serde_with",
+ "thiserror",
 ]
 
 [[package]]
@@ -395,6 +396,26 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "thiserror"
+version = "1.0.32"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f5f6586b7f764adc0231f4c79be7b920e766bb2f3e51b3661cdb263828f19994"
+dependencies = [
+ "thiserror-impl",
+]
+
+[[package]]
+name = "thiserror-impl"
+version = "1.0.32"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "12bafc5b54507e0149cdf1b145a5d80ab80a90bcd9275df43d4fff68460f6c21"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "time"
 version = "0.3.13"

Cargo.toml

@@ -10,3 +10,4 @@ csv = "1.1"
 fpdec = "0.5"
 serde = { version = "1.0", features = ["derive"] }
 serde_with = "2.0"
+thiserror = "1.0"

src/error.rs

@@ -0,0 +1,11 @@
+//! Error types for this crate.
+use thiserror::Error;
+
+/// Any kind of error that can happen when deserializing a [crate::Transaction] value.
+#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Error)]
+pub enum ParseError {
+    #[error("amount not provided")]
+    MissingAmount,
+    #[error("unknown transaction type '{0}'")]
+    UnknownTx(String),
+}

src/lib.rs

@@ -1,5 +1,8 @@
 pub mod core;
 pub use crate::core::*;
 
+pub mod error;
+pub use crate::error::*;
+
 pub mod transaction;
 pub use crate::transaction::*;

src/transaction.rs

@@ -1,5 +1,8 @@
 //! Define all supported transactions.
-use crate::core::{ClientId, TxAmount, TxId};
+use crate::{
+    core::{ClientId, TxAmount, TxId},
+    ParseError,
+};
 
 use serde::Deserialize;
 
@@ -40,8 +43,7 @@ struct TransactionRecord<'a> {
 }
 
 impl TryFrom<TransactionRecord<'_>> for Transaction {
-    // FIXME: use an actual error type.
-    type Error = String;
+    type Error = ParseError;
 
     fn try_from(value: TransactionRecord<'_>) -> Result<Self, Self::Error> {
         let TransactionRecord {
@@ -53,17 +55,17 @@ impl TryFrom<TransactionRecord<'_>> for Transaction {
 
         let transaction = match type_ {
             "deposit" => {
-                let amount = amount.ok_or("Missing amount for transaction")?;
+                let amount = amount.ok_or(ParseError::MissingAmount)?;
                 Transaction::Deposit(Deposit { client, tx, amount })
             }
             "withdrawal" => {
-                let amount = amount.ok_or("Missing amount for transaction")?;
+                let amount = amount.ok_or(ParseError::MissingAmount)?;
                 Transaction::Withdrawal(Withdrawal { client, tx, amount })
             }
             "dispute" => Transaction::Dispute(Dispute { client, tx }),
             "resolve" => Transaction::Resolve(Resolve { client, tx }),
             "chargeback" => Transaction::Chargeback(Chargeback { client, tx }),
-            _ => return Err(format!("Unkown transaction type '{}'", type_)),
+            _ => return Err(ParseError::UnknownTx(type_.into())),
         };
         Ok(transaction)
     }