Omit fractional seconds from http-date format

CHANGELOG.next.toml

@@ -150,3 +150,9 @@ message = "Fix regression with redacting sensitive HTTP response bodies."
 references = ["smithy-rs#2926", "smithy-rs#2972"]
 meta = { "breaking" = false, "tada" = false, "bug" = true, "target" = "client" }
 author = "ysaito1001"
+
+[[smithy-rs]]
+message = "Omit fractional seconds from `date-time` format."
+references = ["smithy-rs#2831"]
+meta = { "breaking" = false, "tada" = false, "bug" = true, "target" = "all" }
+author = "rschmitt"

rust-runtime/aws-smithy-json/src/serialize.rs

@@ -309,7 +309,7 @@ mod tests {
         object.finish();
 
         assert_eq!(
-            r#"{"epoch_seconds":5.2,"date_time":"2021-05-24T15:34:50.123Z","http_date":"Wed, 21 Oct 2015 07:28:00 GMT"}"#,
+            r#"{"epoch_seconds":5.2,"date_time":"2021-05-24T15:34:50Z","http_date":"Wed, 21 Oct 2015 07:28:00 GMT"}"#,
             &output,
         )
     }
@@ -340,7 +340,7 @@ mod tests {
         array.finish();
 
         assert_eq!(
-            r#"[5.2,"2021-05-24T15:34:50.123Z","Wed, 21 Oct 2015 07:28:00 GMT"]"#,
+            r#"[5.2,"2021-05-24T15:34:50Z","Wed, 21 Oct 2015 07:28:00 GMT"]"#,
             &output,
         )
     }

rust-runtime/aws-smithy-query/src/lib.rs

@@ -383,7 +383,7 @@ mod tests {
             "Action=SomeAction\
             &Version=1.0\
             &epoch_seconds=5.2\
-            &date_time=2021-05-24T15%3A34%3A50.123Z\
+            &date_time=2021-05-24T15%3A34%3A50Z\
             &http_date=Wed%2C%2021%20Oct%202015%2007%3A28%3A00%20GMT\
             ",
             out

rust-runtime/aws-smithy-types/src/date_time/format.rs

@@ -452,7 +452,7 @@ pub(crate) mod rfc3339 {
             )
             .into()
         }
-        let (year, month, day, hour, minute, second, micros) = {
+        let (year, month, day, hour, minute, second) = {
             let s = OffsetDateTime::from_unix_timestamp_nanos(date_time.as_nanos())
                 .map_err(out_of_range)?;
             (
@@ -462,7 +462,6 @@ pub(crate) mod rfc3339 {
                 s.hour(),
                 s.minute(),
                 s.second(),
-                s.microsecond(),
             )
         };
 
@@ -479,26 +478,9 @@ pub(crate) mod rfc3339 {
             year, month, day, hour, minute, second
         )
         .unwrap();
-        format_subsecond_fraction(&mut out, micros);
         out.push('Z');
         Ok(out)
     }
-
-    /// Formats sub-second fraction for RFC-3339 (including the '.').
-    /// Expects to be called with a number of `micros` between 0 and 999_999 inclusive.
-    fn format_subsecond_fraction(into: &mut String, micros: u32) {
-        debug_assert!(micros < 1_000_000);
-        if micros > 0 {
-            into.push('.');
-            let (mut remaining, mut place) = (micros, 100_000);
-            while remaining > 0 {
-                let digit = (remaining / place) % 10;
-                into.push(char::from(b'0' + (digit as u8)));
-                remaining -= digit * place;
-                place /= 10;
-            }
-        }
-    }
 }
 
 #[cfg(test)]
@@ -623,7 +605,7 @@ mod tests {
             rfc3339::format(&DateTime::from_secs(-62_135_596_800)).unwrap()
         );
         assert_eq!(
-            "9999-12-31T23:59:59.999999Z",
+            "9999-12-31T23:59:59Z",
             rfc3339::format(&DateTime::from_secs_and_nanos(253402300799, 999_999_999)).unwrap()
         );
 

rust-runtime/aws-smithy-types/src/date_time/mod.rs

@@ -388,7 +388,7 @@ mod test {
         let date_time = DateTime::from_fractional_secs(1576540098, 0.52);
         assert_eq!(
             date_time.fmt(Format::DateTime).unwrap(),
-            "2019-12-16T23:48:18.52Z"
+            "2019-12-16T23:48:18Z"
         );
         assert_eq!(
             date_time.fmt(Format::EpochSeconds).unwrap(),