tail: Apply from review: VerificationResult returns better enums. Inc…

…ludes some small improvements.

src/uu/tail/src/args.rs

@@ -6,7 +6,7 @@
 // spell-checker:ignore (ToDO) kqueue Signum
 
 use crate::paths::Input;
-use crate::{parse, platform, text, Quotable};
+use crate::{parse, platform, Quotable};
 use atty::Stream;
 use clap::{parser::ValueSource, Arg, ArgAction, ArgMatches, Command};
 use same_file::Handle;
@@ -117,8 +117,8 @@ pub enum FollowMode {
 #[derive(Debug)]
 pub enum VerificationResult {
  Ok,
- Fatal(String),
- Exit(i32),
+ CannotFollowStdinByName,
+ NoOutput,
 }
 
 #[derive(Debug, Default)]
@@ -290,10 +290,7 @@ impl Settings {
  pub fn verify(&self) -> VerificationResult {
  // Mimic GNU's tail for `tail -F`
  if self.inputs.iter().any(|i| i.is_stdin()) && self.follow == Some(FollowMode::Name) {
- return VerificationResult::Fatal(format!(
- "cannot follow {} by name",
- text::DASH.quote()
- ));
+ return VerificationResult::CannotFollowStdinByName;
  }
 
  // Mimic GNU's tail for -[nc]0 without -f and exit immediately
@@ -303,7 +300,7 @@ impl Settings {
  FilterMode::Lines(Signum::MinusZero, _) | FilterMode::Bytes(Signum::MinusZero)
  )
  {
- return VerificationResult::Exit(0);
+ return VerificationResult::NoOutput;
  }
 
  VerificationResult::Ok

src/uu/tail/src/tail.rs

@@ -51,8 +51,15 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
  settings.check_warnings();
 
  match settings.verify() {
- args::VerificationResult::Fatal(message) => return Err(USimpleError::new(1, message)),
- args::VerificationResult::Exit(code) => std::process::exit(code),
+ args::VerificationResult::CannotFollowStdinByName => {
+ return Err(USimpleError::new(
+ 1,
+ format!("cannot follow {} by name", text::DASH.quote()),
+ ))
+ }
+ // Exit early if we do not output anything. Note, that this may break a pipe
+ // when tail is on the receiving side.
+ args::VerificationResult::NoOutput => return Ok(()),
  args::VerificationResult::Ok => {}
  }