refactor: Add thiserror to df

src/uu/df/Cargo.toml

@@ -20,6 +20,7 @@ path = "src/df.rs"
 clap = { workspace = true }
 uucore = { workspace = true, features = ["libc", "fsext"] }
 unicode-width = { workspace = true }
+thiserror = { workspace = true }
 
 [dev-dependencies]
 tempfile = { workspace = true }

src/uu/df/src/columns.rs

@@ -4,7 +4,9 @@
 // file that was distributed with this source code.
 // spell-checker:ignore itotal iused iavail ipcent pcent squashfs
 use crate::{OPT_INODES, OPT_OUTPUT, OPT_PRINT_TYPE};
-use clap::{ArgMatches, parser::ValueSource};
+use clap::{parser::ValueSource, ArgMatches};
+use thiserror::Error;
+use uucore::display::Quotable;
 
 /// The columns in the output table produced by `df`.
 ///
@@ -56,9 +58,9 @@ pub(crate) enum Column {
 }
 
 /// An error while defining which columns to display in the output table.
-#[derive(Debug)]
+#[derive(Debug, Error)]
 pub(crate) enum ColumnError {
-    /// If a column appears more than once in the `--output` argument.
+    #[error("{}", .0.quote())]
     MultipleColumns(String),
 }
 

src/uu/df/src/df.rs

@@ -19,10 +19,10 @@ use uucore::{format_usage, help_about, help_section, help_usage, show};
 
 use clap::{Arg, ArgAction, ArgMatches, Command, parser::ValueSource};
 
-use std::error::Error;
 use std::ffi::OsString;
 use std::fmt;
 use std::path::Path;
+use thiserror::Error;
 
 use crate::blocks::{BlockSize, read_block_size};
 use crate::columns::{Column, ColumnError};
@@ -426,28 +426,19 @@ where
     Ok(result)
 }
 
-#[derive(Debug)]
+#[derive(Debug, Error)]
 enum DfError {
     /// A problem while parsing command-line options.
+    #[error("{}", .0)]
     OptionsError(OptionsError),
 }
 
-impl Error for DfError {}
-
 impl UError for DfError {
     fn usage(&self) -> bool {
         matches!(self, Self::OptionsError(OptionsError::ColumnError(_)))
     }
 }
 
-impl fmt::Display for DfError {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match self {
-            Self::OptionsError(e) => e.fmt(f),
-        }
-    }
-}
-
 #[uucore::main]
 pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     let matches = uu_app().try_get_matches_from(args)?;