fixup! Add custom format implementations for ISO 8601, RFC 3339, RFC …

…2822

spec/std/json/serialization_spec.cr

@@ -363,8 +363,14 @@ describe "JSON serialization" do
       {"foo" => {"bar" => 1}}.to_pretty_json(indent: " ").should eq(%({\n "foo": {\n  "bar": 1\n }\n}))
     end
 
-    it "does for time" do
-      Time.utc(2016, 11, 16, 12, 55, 48).to_json.should eq(%("2016-11-16T12:55:48Z"))
+    describe "Time" do
+      it "#to_json" do
+        Time.utc(2016, 11, 16, 12, 55, 48).to_json.should eq(%("2016-11-16T12:55:48Z"))
+      end
+
+      it "omit sub-second precision" do
+        Time.utc(2016, 11, 16, 12, 55, 48, nanosecond: 123456789).to_json.should eq(%("2016-11-16T12:55:48Z"))
+      end
     end
   end
 end

src/json/to_json.cr

@@ -132,7 +132,7 @@ struct Time
   #
   # See `#from_json` for reference.
   def to_json(json : JSON::Builder)
-    json.string(Time::Format::RFC_3339.format(self))
+    json.string(Time::Format::RFC_3339.format(self, fraction_digits: 0))
   end
 end
 

src/time.cr

@@ -896,7 +896,7 @@ struct Time
   # This is similar to `.parse_rfc3339` but RFC 3339 defines a more strict format.
   # In ISO 8601 for examples, field delimiters (`-`, `:`) are optional.
   #
-  # Use `#to_rfc3339` to format a `Time` according to ISO 8601.
+  # Use `#to_rfc3339` to format a `Time` according to .
   def self.parse_iso8601(time : String)
     Format::ISO_8601_DATE_TIME.parse(time)
   end

src/time/format/custom/rfc_3339.cr

@@ -9,26 +9,26 @@ struct Time::Format
     end
 
     # Formats a `Time` into the given *io*.
-    def self.format(time : Time, io : IO)
+    def self.format(time : Time, io : IO, fraction_digits = nil)
       formatter = Formatter.new(time, io)
-      formatter.rfc_3339
+      formatter.rfc_3339(fraction_digits: fraction_digits)
       io
     end
 
     # Formats a `Time` into a `String`.
-    def self.format(time : Time)
+    def self.format(time : Time, fraction_digits = nil)
       String.build do |io|
-        format(time, io)
+        format(time, io, fraction_digits: fraction_digits)
       end
     end
   end
 
   module Pattern
-    def rfc_3339
+    def rfc_3339(fraction_digits = nil)
       year_month_day
       char 'T', 't', ' '
       twenty_four_hour_time_with_seconds
-      second_fraction?
+      second_fraction?(fraction_digits: fraction_digits)
       time_zone_z_or_offset(force_colon: true)
     end
   end

src/time/format/formatter.cr

@@ -135,8 +135,8 @@ struct Time::Format
       nanoseconds
     end
 
-    def second_fraction?
-      unless time.nanosecond == 0
+    def second_fraction?(fraction_digits = nil)
+      unless time.nanosecond == 0 || fraction_digits == 0
         char '.'
         second_fraction
       end

src/time/format/parser.cr

@@ -237,7 +237,7 @@ struct Time::Format
       @nanosecond = (decimals * 10 ** (precision_shift + nanoseconds_shift)).to_i
     end
 
-    def second_fraction?
+    def second_fraction?(fraction_digits = nil)
       if current_char == '.'
         next_char
         nanoseconds