Add support for fractional timestamps

codegen/smithy-ruby-codegen/src/main/java/software/amazon/smithy/ruby/codegen/util/ParamsToHash.java

@@ -196,7 +196,7 @@ public String timestampShape(TimestampShape shape) {
                 // rounding of floats cause an issue in the precision of fractional seconds
                 Double n = node.expectNumberNode().getValue().doubleValue();
                 long seconds = (long) Math.floor(n);
-                long ms = (long) ((n - Math.floor(n)) * 1000);
+                long ms = Math.round((n - Math.floor(n)) * 1000);
                 return "Time.at(" + seconds + ", " + ms + ", :millisecond)";
             } else {
                 return "Time.at(" + node.expectNumberNode().getValue().toString() + ")";

codegen/smithy-ruby-rails-codegen-test/model/protocol-test/kitchen-sink.smithy

@@ -168,6 +168,22 @@ use smithy.test#httpResponseTests
         method: "POST",
         uri: "/",
     },
+    {
+        id: "rails_json_serializes_fractional_timestamp_shapes",
+        protocol: railsJson,
+        documentation: "Serializes fractional timestamp shapes",
+        body: "{\"timestamp\":\"2000-01-02T20:34:56.123Z\"}",
+        bodyMediaType: "application/json",
+        headers: {"Content-Type": "application/json"},
+        requireHeaders: [
+            "Content-Length"
+        ],
+        params: {
+            Timestamp: 946845296.123,
+        },
+        method: "POST",
+        uri: "/",
+    },
     {
         id: "rails_json_serializes_timestamp_shapes_with_iso8601_timestampformat",
         protocol: railsJson,
@@ -664,6 +680,18 @@ use smithy.test#httpResponseTests
         },
         code: 200,
     },
+    {
+        id: "rails_json_parses_fractional_timestamp_shapes",
+        protocol: railsJson,
+        documentation: "Parses fractional timestamp shapes",
+        body: "{\"timestamp\":\"2000-01-02T20:34:56.123Z\"}",
+        bodyMediaType: "application/json",
+        headers: {"Content-Type": "application/json"},
+        params: {
+            Timestamp: 946845296.123,
+        },
+        code: 200,
+    },
     {
         id: "rails_json_parses_iso8601_timestamps",
         protocol: railsJson,
@@ -688,6 +716,18 @@ use smithy.test#httpResponseTests
         },
         code: 200,
     },
+    {
+        id: "rails_json_parses_fractional_httpdate_timestamps",
+        protocol: railsJson,
+        documentation: "Parses fractional httpdate timestamps",
+        body: "{\"httpdate_timestamp\":\"Sun, 02 Jan 2000 20:34:56.123 GMT\"}",
+        bodyMediaType: "application/json",
+        headers: {"Content-Type": "application/json"},
+        params: {
+            HttpdateTimestamp: 946845296.123,
+        },
+        code: 200,
+    },
     {
         id: "rails_json_parses_list_shapes",
         protocol: railsJson,

hearth/lib/hearth/time_helper.rb

@@ -11,7 +11,8 @@ class << self
       # @param [Time] time
       # @return [String<Date Time>] The time as an ISO8601 string.
       def to_date_time(time)
-        time.utc.strftime('%Y-%m-%dT%H:%M:%SZ')
+        optional_ms_digits = time.subsec.zero? ? nil : 3
+        time.utc.iso8601(optional_ms_digits)
       end
 
       # @param [Time] time
@@ -28,7 +29,8 @@ def to_epoch_seconds(time)
       # @return [String<Http Date>] Returns the time formatted
       #   as an HTTP header date.
       def to_http_date(time)
-        time.utc.httpdate
+        fractional = '.%L' unless time.subsec.zero?
+        time.utc.strftime("%a, %d %b %Y %H:%M:%S#{fractional} GMT")
       end
     end
   end

hearth/spec/hearth/time_helper_spec.rb

@@ -8,18 +8,40 @@ module Hearth
       it 'converts a time object to date time format' do
         expect(subject.to_date_time(time)).to eq '1970-01-01T00:00:00Z'
       end
+
+      context 'fractional seconds' do
+        let(:time) { Time.at(946_845_296, 123, :millisecond) }
+        it 'converts to date time format with milliseconds' do
+          expect(subject.to_date_time(time)).to eq '2000-01-02T20:34:56.123Z'
+        end
+      end
     end
 
     describe '.to_epoch_seconds' do
       it 'converts a time object to epoch seconds format' do
         expect(subject.to_epoch_seconds(time)).to eq 0.0
       end
+
+      context 'fractional seconds' do
+        let(:time) { Time.at(946_845_296, 123, :millisecond) }
+        it 'converts to date time format with milliseconds' do
+          expect(subject.to_epoch_seconds(time)).to eq 946_845_296.123
+        end
+      end
     end
 
     describe '.to_http_date' do
       it 'converts a time object to http date format' do
         expect(subject.to_http_date(time)).to eq 'Thu, 01 Jan 1970 00:00:00 GMT'
       end
+
+      context 'fractional seconds' do
+        let(:time) { Time.at(946_845_296, 123, :millisecond) }
+        it 'converts to http date format with milliseconds' do
+          expect(subject.to_http_date(time))
+            .to eq 'Sun, 02 Jan 2000 20:34:56.123 GMT'
+        end
+      end
     end
   end
 end