chore(solc): improve remapping errors (#1570)

* chore(solc): improve remapping errors

* fix: update error names

* chore: rename test

ethers-solc/src/remappings.rs

@@ -67,22 +67,26 @@ impl Remapping {
 
 #[derive(thiserror::Error, Debug, PartialEq, Eq, PartialOrd)]
 pub enum RemappingError {
-    #[error("no prefix found")]
-    NoPrefix,
-    #[error("no target found")]
-    NoTarget,
+    #[error("invalid remapping format, found `{0}`, expected `<key>=<value>`")]
+    InvalidRemapping(String),
+    #[error("remapping key can't be empty, found `{0}`, expected `<key>=<value>`")]
+    EmptyRemappingKey(String),
+    #[error("remapping value must be a path, found `{0}`, expected `<key>=<value>`")]
+    EmptyRemappingValue(String),
 }
 
 impl FromStr for Remapping {
     type Err = RemappingError;
 
-    fn from_str(remapping: &str) -> std::result::Result<Self, Self::Err> {
-        let (name, path) = remapping.split_once('=').ok_or(RemappingError::NoPrefix)?;
+    fn from_str(remapping: &str) -> Result<Self, Self::Err> {
+        let (name, path) = remapping
+            .split_once('=')
+            .ok_or_else(|| RemappingError::InvalidRemapping(remapping.to_string()))?;
         if name.trim().is_empty() {
-            return Err(RemappingError::NoPrefix)
+            return Err(RemappingError::EmptyRemappingKey(remapping.to_string()))
         }
         if path.trim().is_empty() {
-            return Err(RemappingError::NoTarget)
+            return Err(RemappingError::EmptyRemappingValue(remapping.to_string()))
         }
         Ok(Remapping { name: name.to_string(), path: path.to_string() })
     }
@@ -743,17 +747,17 @@ mod tests {
     }
 
     #[test]
-    fn serde() {
+    fn remapping_errors() {
         let remapping = "oz=../b/c/d";
         let remapping = Remapping::from_str(remapping).unwrap();
         assert_eq!(remapping.name, "oz".to_string());
         assert_eq!(remapping.path, "../b/c/d".to_string());
 
         let err = Remapping::from_str("").unwrap_err();
-        assert_eq!(err, RemappingError::NoPrefix);
+        matches!(err, RemappingError::InvalidRemapping(_));
 
         let err = Remapping::from_str("oz=").unwrap_err();
-        assert_eq!(err, RemappingError::NoTarget);
+        matches!(err, RemappingError::EmptyRemappingValue(_));
     }
 
     // <https://doc.rust-lang.org/rust-by-example/std_misc/fs.html>