sum: return UResult from uumain() function

src/uu/sum/src/sum.rs

@@ -12,9 +12,10 @@ extern crate uucore;
 
 use clap::{crate_version, App, Arg};
 use std::fs::File;
-use std::io::{stdin, Read, Result};
+use std::io::{stdin, Read};
 use std::path::Path;
 use uucore::display::Quotable;
+use uucore::error::{FromIo, UResult, USimpleError};
 use uucore::InvalidEncodingHandling;
 
 static NAME: &str = "sum";
@@ -65,26 +66,25 @@ fn sysv_sum(mut reader: Box<dyn Read>) -> (usize, u16) {
     (blocks_read, ret as u16)
 }
 
-fn open(name: &str) -> Result<Box<dyn Read>> {
+fn open(name: &str) -> UResult<Box<dyn Read>> {
     match name {
         "-" => Ok(Box::new(stdin()) as Box<dyn Read>),
         _ => {
             let path = &Path::new(name);
             if path.is_dir() {
-                return Err(std::io::Error::new(
-                    std::io::ErrorKind::InvalidInput,
-                    "Is a directory",
+                return Err(USimpleError::new(
+                    2,
+                    format!("{}: Is a directory", name.maybe_quote()),
                 ));
             };
             // Silent the warning as we want to the error message
-            #[allow(clippy::question_mark)]
             if path.metadata().is_err() {
-                return Err(std::io::Error::new(
-                    std::io::ErrorKind::NotFound,
-                    "No such file or directory",
+                return Err(USimpleError::new(
+                    2,
+                    format!("{}: No such file or directory", name.maybe_quote()),
                 ));
             };
-            let f = File::open(path)?;
+            let f = File::open(path).map_err_context(String::new)?;
             Ok(Box::new(f) as Box<dyn Read>)
         }
     }
@@ -96,7 +96,8 @@ mod options {
     pub static SYSTEM_V_COMPATIBLE: &str = "sysv";
 }
 
-pub fn uumain(args: impl uucore::Args) -> i32 {
+#[uucore_procs::gen_uumain]
+pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     let args = args
         .collect_str(InvalidEncodingHandling::ConvertLossy)
         .accept_any();
@@ -116,13 +117,11 @@ pub fn uumain(args: impl uucore::Args) -> i32 {
         files.len() > 1
     };
 
-    let mut exit_code = 0;
     for file in &files {
         let reader = match open(file) {
             Ok(f) => f,
             Err(error) => {
-                show_error!("{}: {}", file.maybe_quote(), error);
-                exit_code = 2;
+                show!(error);
                 continue;
             }
         };
@@ -138,8 +137,7 @@ pub fn uumain(args: impl uucore::Args) -> i32 {
             println!("{} {}", sum, blocks);
         }
     }
-
-    exit_code
+    Ok(())
 }
 
 pub fn uu_app() -> App<'static, 'static> {