groups: move to thiserror

src/uu/groups/Cargo.toml

@@ -18,6 +18,7 @@ path = "src/groups.rs"
 
 [dependencies]
 clap = { workspace = true }
+thiserror = { workspace = true }
 uucore = { workspace = true, features = ["entries", "process"] }
 
 [[bin]]

src/uu/groups/src/groups.rs

@@ -12,8 +12,7 @@
 
 // spell-checker:ignore (ToDO) passwd
 
-use std::error::Error;
+use thiserror::Error;
-use std::fmt::Display;
 use uucore::{
     display::Quotable,
     entries::{get_groups_gnu, gid2grp, Locate, Passwd},
@@ -29,26 +28,20 @@ mod options {
 const ABOUT: &str = help_about!("groups.md");
 const USAGE: &str = help_usage!("groups.md");
 
-#[derive(Debug)]
+#[derive(Debug, Error)]
 enum GroupsError {
+    #[error("failed to fetch groups")]
     GetGroupsFailed,
+
+    #[error("cannot find name for group ID {0}")]
     GroupNotFound(u32),
+
+    #[error("{user}: no such user", user = .0.quote())]
     UserNotFound(String),
 }
 
-impl Error for GroupsError {}
 impl UError for GroupsError {}
 
-impl Display for GroupsError {
-    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
-        match self {
-            Self::GetGroupsFailed => write!(f, "failed to fetch groups"),
-            Self::GroupNotFound(gid) => write!(f, "cannot find name for group ID {gid}"),
-            Self::UserNotFound(user) => write!(f, "{}: no such user", user.quote()),
-        }
-    }
-}
-
 fn infallible_gid2grp(gid: &u32) -> String {
     match gid2grp(*gid) {
         Ok(grp) => grp,