Implement Display for Duration

src/duration.rs

@@ -740,6 +740,44 @@ impl Duration {
 }
 
 // region: trait impls
+/// The format returned by this implementation is not stable and must not be relied upon.
+///
+/// For the purposes of this implementation, a day is exactly 24 hours and a minute is exactly 60
+/// seconds.
+impl fmt::Display for Duration {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        /// Format a single item.
+        macro_rules! item {
+            ($name:literal, $value:expr) => {
+                match $value {
+                    0 => Ok(()),
+                    value => value.fmt(f).and(f.write_str($name)),
+                }
+            };
+        }
+
+        if self.is_zero() {
+            return f.write_str("0s");
+        }
+
+        let seconds = self.seconds.unsigned_abs();
+        let nanoseconds = self.nanoseconds.unsigned_abs();
+
+        if self.is_negative() {
+            f.write_str("-")?;
+        }
+
+        item!("d", seconds / 86_400)?;
+        item!("h", seconds / 3_600 % 24)?;
+        item!("m", seconds / 60 % 60)?;
+        item!("s", seconds % 60)?;
+        item!("ms", nanoseconds / 1_000_000)?;
+        item!("µs", nanoseconds / 1_000 % 1_000)?;
+        item!("ns", nanoseconds % 1_000)?;
+        Ok(())
+    }
+}
+
 impl TryFrom<StdDuration> for Duration {
     type Error = error::ConversionRange;
 

tests/integration/duration.rs

@@ -367,6 +367,38 @@ fn time_fn() {
     assert_eq!(value, 0);
 }
 
+#[test]
+fn display() {
+    assert_eq!(0.seconds().to_string(), "0s");
+    assert_eq!(60.days().to_string(), "60d");
+    assert_eq!((-48).hours().to_string(), "-2d");
+    assert_eq!(48.hours().to_string(), "2d");
+    assert_eq!(1.minutes().to_string(), "1m");
+    assert_eq!(10.minutes().to_string(), "10m");
+    assert_eq!(1.seconds().to_string(), "1s");
+    assert_eq!(10.seconds().to_string(), "10s");
+    assert_eq!(1.milliseconds().to_string(), "1ms");
+    assert_eq!(10.milliseconds().to_string(), "10ms");
+    assert_eq!(100.milliseconds().to_string(), "100ms");
+    assert_eq!(1.microseconds().to_string(), "1µs");
+    assert_eq!(10.microseconds().to_string(), "10µs");
+    assert_eq!(100.microseconds().to_string(), "100µs");
+    assert_eq!(1.nanoseconds().to_string(), "1ns");
+    assert_eq!(10.nanoseconds().to_string(), "10ns");
+    assert_eq!(100.nanoseconds().to_string(), "100ns");
+
+    assert_eq!(1.days().to_string(), "1d");
+    assert_eq!(26.hours().to_string(), "1d2h");
+    assert_eq!(1_563.minutes().to_string(), "1d2h3m");
+    assert_eq!(93_784.seconds().to_string(), "1d2h3m4s");
+    assert_eq!(93_784_005.milliseconds().to_string(), "1d2h3m4s5ms");
+    assert_eq!(93_784_005_006.microseconds().to_string(), "1d2h3m4s5ms6µs");
+    assert_eq!(
+        93_784_005_006_007.nanoseconds().to_string(),
+        "1d2h3m4s5ms6µs7ns"
+    );
+}
+
 #[test]
 fn try_from_std_duration() {
     assert_eq!(Duration::try_from(0.std_seconds()), Ok(0.seconds()));