date: Rework argument processing

src/uu/date/src/date.rs

@@ -91,6 +91,7 @@ enum DateSource {
     Now,
     Custom(String),
     File(PathBuf),
+    Reference(PathBuf),
     Stdin,
     Human(TimeDelta),
 }
@@ -178,11 +179,23 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
             "-" => DateSource::Stdin,
             _ => DateSource::File(file.into()),
         }
+    } else if let Some(file) = matches.get_one::<String>(OPT_REFERENCE) {
+        DateSource::Reference(file.into())
     } else {
         DateSource::Now
     };
 
-    let set_to = match matches.get_one::<String>(OPT_SET).map(parse_date) {
+    let set_option = matches.get_one::<String>(OPT_SET);
+
+    // Before parsing an eventual OPT_SET, check if it can't be present.
+    if !matches!(date_source, DateSource::Now) && set_option.is_some() {
+        return Err(USimpleError::new(
+            1,
+            "the options to print and set the time may not be used together",
+        ));
+    }
+
+    let set_to = match set_option.map(parse_date) {
         None => None,
         Some(Err((input, _err))) => {
             return Err(USimpleError::new(
@@ -260,6 +273,11 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
                 let iter = lines.map_while(Result::ok).map(parse_date);
                 Box::new(iter)
             }
+            DateSource::Reference(ref path) => {
+                let modified_time: std::time::SystemTime = std::fs::metadata(path)?.modified()?;
+                let chrono_time: DateTime<Local> = modified_time.into();
+                Box::new(std::iter::once(Ok(chrono_time.into())))
+            }
             DateSource::Now => {
                 let iter = std::iter::once(Ok(now));
                 Box::new(iter)
@@ -318,15 +336,21 @@ pub fn uu_app() -> Command {
                 .short('d')
                 .long(OPT_DATE)
                 .value_name("STRING")
-                .help("display time described by STRING, not 'now'"),
+                .action(ArgAction::Set)
+                .overrides_with(OPT_DATE)
+                .help("display time described by STRING, not 'now'")
+                .conflicts_with_all([OPT_FILE, OPT_REFERENCE]),
         )
         .arg(
             Arg::new(OPT_FILE)
                 .short('f')
                 .long(OPT_FILE)
                 .value_name("DATEFILE")
                 .value_hint(clap::ValueHint::FilePath)
-                .help("like --date; once for each line of DATEFILE"),
+                .action(ArgAction::Set)
+                .overrides_with(OPT_FILE) // several -f can be passed, but only the last is kept.
+                .help("like --date; once for each line of DATEFILE")
+                .conflicts_with_all([OPT_REFERENCE]),
         )
         .arg(
             Arg::new(OPT_ISO_8601)
@@ -366,6 +390,8 @@ pub fn uu_app() -> Command {
                 .long(OPT_REFERENCE)
                 .value_name("FILE")
                 .value_hint(clap::ValueHint::AnyPath)
+                .action(ArgAction::Set)
+                .overrides_with(OPT_REFERENCE)
                 .help("display the last modification time of FILE"),
         )
         .arg(

tests/by-util/test_date.rs

@@ -1,3 +1,5 @@
+use std::time::SystemTime;
+
 // This file is part of the uutils coreutils package.
 //
 // For the full copyright and license information, please view the LICENSE
@@ -478,3 +480,78 @@ fn test_date_from_stdin() {
              Sat Apr 15 18:30:00 2023\n",
         );
 }
+
+#[test]
+fn test_date_exclusive_date_sources() {
+    new_ucmd!()
+        .arg("-f")
+        .arg("foo.txt")
+        .arg("-d")
+        .arg("1111-11-11")
+        .fails()
+        .stderr_matches(&Regex::new("error: the argument .* cannot be used with .*").unwrap());
+
+    new_ucmd!()
+        .arg("-r")
+        .arg("foo.txt")
+        .arg("-d")
+        .arg("1111-11-11")
+        .fails()
+        .stderr_matches(&Regex::new("error: the argument .* cannot be used with .*").unwrap());
+
+    new_ucmd!()
+        .arg("-r")
+        .arg("foo.txt")
+        .arg("-f")
+        .arg("bar.txt")
+        .fails()
+        .stderr_matches(&Regex::new("error: the argument .* cannot be used with .*").unwrap());
+}
+
+#[test]
+fn test_date_successive_file() {
+    const FILE: &str = "file-with-dates";
+    let (at, mut ucmd) = at_and_ucmd!();
+
+    at.write(
+        FILE,
+        "2023-03-27 08:30:00\n\
+         2023-04-01 12:00:00\n\
+         2023-04-15 18:30:00",
+    );
+    ucmd.arg("-f")
+        .arg("not-existent-file")
+        .arg("-f")
+        .arg("file-with-dates")
+        .succeeds();
+}
+
+#[test]
+fn test_date_reference() {
+    let (at, mut ucmd) = at_and_ucmd!();
+
+    at.touch_and_set_modified("ref-file", SystemTime::UNIX_EPOCH);
+
+    ucmd.arg("-r")
+        .arg("ref-file")
+        .succeeds()
+        .stdout_is("Thu Jan  1 00:00:00 1970\n");
+}
+
+#[test]
+fn test_date_successive_reference() {
+    const FILE: &str = "file-with-dates";
+    let (at, mut ucmd) = at_and_ucmd!();
+
+    at.write(
+        FILE,
+        "2023-03-27 08:30:00\n\
+         2023-04-01 12:00:00\n\
+         2023-04-15 18:30:00",
+    );
+    ucmd.arg("-r")
+        .arg("not-existent-file")
+        .arg("-r")
+        .arg("file-with-dates")
+        .succeeds();
+}

tests/common/util.rs

@@ -46,7 +46,7 @@ use std::process::{Child, Command, ExitStatus, Output, Stdio};
 use std::rc::Rc;
 use std::sync::mpsc::{self, RecvTimeoutError};
 use std::thread::{sleep, JoinHandle};
-use std::time::{Duration, Instant};
+use std::time::{Duration, Instant, SystemTime};
 use std::{env, hint, mem, thread};
 use tempfile::{Builder, TempDir};
 
@@ -974,6 +974,13 @@ impl AtPath {
         File::create(self.plus(file)).unwrap();
     }
 
+    pub fn touch_and_set_modified<P: AsRef<Path>>(&self, file: P, modified: SystemTime) {
+        let file = file.as_ref();
+        log_info("touch", self.plus_as_string(file));
+        let f = File::create(self.plus(file)).unwrap();
+        f.set_modified(modified).unwrap();
+    }
+
     #[cfg(not(windows))]
     pub fn mkfifo(&self, fifo: &str) {
         let full_path = self.plus_as_string(fifo);