Fix PgInterval display formatting

Correct pluralization of years, months, and days in display. Correctly
format the time part, including sign for negative intervals. Fix the
test case to match the new format.

Author: lovasoa

sqlx-core/src/postgres/types/interval.rs

@@ -96,14 +96,14 @@ impl std::fmt::Display for PgInterval {
                 parts.push(format!(
                     "{} year{}",
                     years,
-                    if years != 1 { "s" } else { "" }
+                    if years.abs() != 1 { "s" } else { "" }
                 ));
             }
             if months != 0 {
                 parts.push(format!(
                     "{} mon{}",
                     months,
-                    if months != 1 { "s" } else { "" }
+                    if months.abs() != 1 { "s" } else { "" }
                 ));
             }
         }
@@ -112,27 +112,29 @@ impl std::fmt::Display for PgInterval {
             parts.push(format!(
                 "{} day{}",
                 self.days,
-                if self.days != 1 { "s" } else { "" }
+                if self.days.abs() != 1 { "s" } else { "" }
             ));
         }
 
-        let total_seconds = self.microseconds / 1_000_000;
-        let microseconds = self.microseconds % 1_000_000;
-        let hours = total_seconds / 3600;
-        let minutes = (total_seconds % 3600) / 60;
-        let seconds = total_seconds % 60;
+        let time_us = self.microseconds;
+
+        if time_us != 0 || parts.is_empty() {
+            let sign = if time_us < 0 { "-" } else { "" };
+            let us = time_us.abs();
+
+            let total_seconds = us / 1_000_000;
+            let microseconds = us % 1_000_000;
+            let hours = total_seconds / 3600;
+            let minutes = (total_seconds % 3600) / 60;
+            let seconds = total_seconds % 60;
 
-        if hours != 0 || minutes != 0 || seconds != 0 || microseconds != 0 {
             let time_part = if microseconds != 0 {
                 format!(
-                    "{:02}:{:02}:{:02}.{:06}",
-                    hours,
-                    minutes,
-                    seconds,
-                    microseconds.abs()
+                    "{}{:02}:{:02}:{:02}.{:06}",
+                    sign, hours, minutes, seconds, microseconds
                 )
             } else {
-                format!("{:02}:{:02}:{:02}", hours, minutes, seconds)
+                format!("{}{:02}:{:02}:{:02}", sign, hours, minutes, seconds)
             };
             parts.push(time_part);
         }
@@ -499,7 +501,7 @@ fn test_pginterval_display() {
     let interval = PgInterval {
         months: 0,
         days: 0,
-        microseconds: 3_660_000_000 + 30_000, // 1 hour 1 minute 30 microseconds
+        microseconds: 3_600 * 1_000_000 + 60 * 1_000_000 + 30, // 1 hour 1 minute 30 microseconds
     };
     assert_eq!(interval.to_string(), "01:01:00.000030");
 
@@ -531,11 +533,11 @@ fn test_pginterval_display() {
     let interval = PgInterval {
         months: 14, // 1 year 2 months
         days: 27,
-        microseconds: 43_200_000_000 + 180_000_000 + 30_000, // 12 hours 3 minutes 30 microseconds
+        microseconds: 43_200_000_000 + 180_000_000 + 30_000, // 12 hours 3 minutes 30 milliseconds
     };
     assert_eq!(
         interval.to_string(),
-        "1 year 2 mons 27 days 12:03:00.000030"
+        "1 year 2 mons 27 days 12:03:00.030000"
     );
 
     // Negative microseconds
@@ -544,5 +546,5 @@ fn test_pginterval_display() {
         days: 0,
         microseconds: -1_000_000, // -1 second
     };
-    assert_eq!(interval.to_string(), "00:00:01.000000");
+    assert_eq!(interval.to_string(), "-00:00:01");
 }