Add custom time format implementations by straight-shoota · Pull Request #5123 · crystal-lang/crystal

straight-shoota · 2017-10-15T01:45:01Z

The format patterns from Time::Format allow to define simple date formats but they are quite limited in flexibility. Many standardized formats include slight variations which must be taken into account for parsing such formats in a standards-compliant way.

This PR adds custom format implementations for some well-used time formats.
For a few it adds adds short-cut methods to Time class (like Time.parse_iso8601).

Time::Format::ISO_8601_DATETIME: Parser for standard time format with many variations. It should support most of the standard format including week dates, ordinal dates and optional separators. Uses RFC 3339 as formatter.
Time::Format::RFC_3339: More strict variation of ISO 8601, recommended for exchanging time data in computer systems.
Time::Format::RFC_2822: Format compatible to RFC 822 and RFC 1123 used for example in HTTP protocols.
Time::Format::HTTP_DATE: Proper implementation of HTTP.parse_date supporting time formats expressed as RFC 1123/RFC 2822, RFC 850 or asctime which are used by many HTTP protocols. Uses RFC_2822 as formatter.
Time::Format::YAML_DATE: Refactored implementation of parser for YAML datetime type.

Surpasses #5084, #4729

/cc @asterite @RX14

Sija · 2017-10-15T09:32:03Z

+      when Time::Kind::Local
+        time_zone_rfc2822
+      else
+        raise "invalid timezone"


Capitalize exception message, please.

straight-shoota · 2017-12-15T16:34:35Z

I've rebased this PR and refactored a bit. It would be great to get some feedback.

straight-shoota · 2018-03-07T22:50:15Z

I've rebased this PR to incorporate the Time::Location API added in #5324.

Requires #5786

bcardiff

@straight-shoota

may I ask to rebase this PR on master?
if #5382 is merged we are mostly ok since we will have proper timezone parsing exception but adds a quick-hack, and it would be more proper to include this PR instead of #5382. Am I right?
Is there anything pending that you have in mind as a follow up for this PR?

These adds some breaking-changes so having a rebase would be helpful to check the impact.

bcardiff · 2018-06-05T09:59:10Z

    it "without time zone" do
      time = Time.utc(1994, 11, 6, 8, 49, 37, nanosecond: 0)
-      HTTP.rfc1123_date(time).should eq("Sun, 06 Nov 1994 08:49:37 GMT")
+      HTTP.format_time(time).should eq("Sun, 6 Nov 1994 08:49:37 GMT")


The preferred format is with two day digits as of https://tools.ietf.org/html/rfc7231#section-7.1.1.1 and https://tools.ietf.org/html/rfc2616#page-21

Somehow I would prefer rfc/iso in the function names for the format.

The name was changed because the methods doesn't implement one exact standard format but generally format and parse time instances for use in a HTTP protocol context (see previous comments in #4729 (comment)).

I'll look into the preferred digit format.

bcardiff · 2018-06-05T10:23:03Z

+  end
+
+  # DEPRECATED: Use `HTTP.format_time` instead.
+  def self.rfc1123_time(time : Time) : String


Why this is left and marked as deprecated and rfc1123_date dropped completely? I think is either both or none.

Yeah, it needs to be removed.

bcardiff · 2018-06-05T10:26:40Z

 struct Time
  def to_json(json : JSON::Builder)
-    json.string(Time::Format::ISO_8601_DATE_TIME.format(self))
+    json.string(Time::Format::RFC_3339.format(self))


Why this change if ISO_8601 is still defined?

The difference is mostly negligible, but RFC 3339 is generally the better (stricter) format for this purpose. ISO_8601_DATE_TIME by default formats a offset as HHmm while RFC 3339 requires a colon: HH:mm

The JSON specification doesn't include a Date data type, so it's up to the implementation. JavaScript's Date.toJSON() actually is RFC 3339 compliant (YYYY-MM-DDTHH:mm:ss.sssZ).

The references I found said ISO8601 is the format used in Javascript. I think we should stick to 8601 here. Actually been less stricter is better IMO since an API built on top of this would be less pedantic to the user.

https://www.w3schools.com/jsref/jsref_tojson.asp

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/toISOString

True, this is a bit confusing because RFC 3339 actually is ISO 8601. But RFC 3339 is better suited as machine-parsed exchange format. That's why I'm pretty convinced we should use RFC 3339 as output format for #to_json.

I left RFC_3339 here but it returns the exact same result as ISO_8601_DATE_TIME.

straight-shoota · 2018-06-05T11:47:27Z

Thanks for taking a look at this!

Done.
Exactly. Ensure time parser raises if timezone is missing #5382 was supposed to be a quick bug fix, but it's been stalled for so long it would probably be better to just forget it and merge this one directly.
I don't think I had any further plans. Maybe I forgot... it's been a long time.

RX14 · 2018-06-06T10:47:56Z


    it "deserializes Time" do
-      Time.from_json(%("2016-11-16T09:55:48-0300")).to_utc.should eq(Time.utc(2016, 11, 16, 12, 55, 48))
+      Time.from_json(%("2016-11-16T09:55:48-03:00")).to_utc.should eq(Time.utc(2016, 11, 16, 12, 55, 48))


We shouldn't break this

According to #5123 (comment)
I agree. The JSON format should be ISO8601 by default.

Output should be the RFC 3339 flavour of ISO 8601, the parser should accept more variants. That's probably the best solution.

bcardiff · 2018-06-06T15:35:57Z

@straight-shoota

Any further arguments on Add custom time format implementations #5123 (comment) ? Why emitting in RFC3339 is better since the default in JavaScript is ISO8601? Luckily in utc they both use Z suffix. Although the added : is still ISO8601 compatible, we should be fine. @RX14 do you agree?
I noticed that now nanoseconds will be rendered in to_json while before only seconds were used. This was also aligned with go behaviour that includes a separata formatter for just seconds and nano seconds. Could you change the formatter to emit only seconds as before? I don't have a strong opinion to add a 3339Nano formatter but the extra precision might be problematic in some system where just milliseconds are supported.

After 2 is addressed is a 👍 from me (and a big 🙇 for all the time re work)

straight-shoota · 2018-06-06T16:48:21Z

There is no difference. ISO_8601_DATE_TIME would also use a colon in the offset, and that's how it should be. JavaScript's Date.toJSON() serializes in UTC only, by the way.
Good catch! We need more specs for these things 😆 But: should the default format entirely omit sub-second precision or round to milliseconds? (that's what Date.toJSON() does). Though it probably won't be much of a difference, applications that understand milliseconds should probably be smart enough to digest a few extra digits.
There is no specification for any of this anyway, so we might as well use the best prevision available. If that doesn't work for some use case, it's easy to employ a custom formatter with a different format.

bcardiff · 2018-06-06T17:13:38Z

Ok
I would prefer the default to be the option that will broadly work. So seconds without fraction. If needed later a 3339Nano formatter can be added. If a spec to ensure sub-second are drop is added definitely will be a plus

If you prefer me to made the changes in 2 let me know.

straight-shoota · 2018-06-06T20:07:38Z

Done. To accomplish this, I added a fraction_digits parameter to RFC_3339.format which I think would be generally useful and could be expanded. But that's probably something for a subsequent PR because this needs proper thought.

RX14

I don't like that there are changes to time/format/formatter.cr and time/format/parser.cr, and I don't like that there are new methods just moneypatched in to the existing parser and formatter, instead of being inherited or stuff being put in a module.

RX14 · 2018-06-07T13:11:31Z

+# * **%3N**, **%L**: milliseconds, zero padded (000, 001, ..., 999)
+# * **%6N**: microseconds, zero padded (000000, 000001, ..., 999999)
+# * **%9N**: nanoseconds, zero padded (000000000, 000000001, ..., 999999999)
+# * **%N**: second fraction, zero padded. (Same as `%9N` but may consume more than 9 digits while parsing)


Why this doc change?

It helps discoverability if the directives are lexically ordered. It's unrelated, though. If you like, I can make a separate PR for this.

RX14 · 2018-06-07T13:12:58Z

    end

+    def full_or_short_year
+      year


Why an alias?

The parser has a different implementation.

RX14 · 2018-06-07T13:15:22Z

      io << get_short_day_name.upcase
    end

+    def short_day_name_with_comma?


This is a duplicate definition.

Where's the duplicate?

Sorry I meant https://github.com/crystal-lang/crystal/pull/5123/files#diff-61fcbccde80bde3628b08077c5d0e22cR171 is overridden by https://github.com/crystal-lang/crystal/pull/5123/files#diff-819208e2dbfe2071e14f02023b5148d0R66.

straight-shoota · 2018-06-07T14:04:55Z

@RX14 You mean more like #5084? That design has been abandoned for good, I hope. This is the best I can think of and I don't see any problems with monkey patching a few specific methods nor any benefits in extracting them to modules.
We could put the specialized methods directly into the formatter.cr/parser.cr types to avoid monkey patching, but I think having these implementations in separate files is better code organization. All pattern methods defined in a custom files are only used within that file and namespaces with the format name.

RX14

I still don't get why time/format/formatter.cr and time/format/parser.cr are changed. If these still have the same functionality, why do they suddenly have extra unused methods? If you're going tor refactor core time formatter stuff, it should at the very least be in a seperate commit.

RX14 · 2018-06-08T16:43:57Z

 # * **%_m**: month number, blank padded (" 1", " 2", ..., "12")
 # * **%-m**: month number (1, 2, ..., 12)
 # * **%M**: minute, zero padded (00, 01, 02, ..., 59)
+# * **%3N**, **%L**: milliseconds, zero padded (000, 001, ..., 999)


duplicate definition of L

straight-shoota · 2018-06-08T18:02:05Z

They provide additional methods that are used by several specific formats. So there is added functionality for the core formatter/parser feature. Refactoring is actually in 0c242b0.

RX14 · 2018-06-09T16:28:24Z

Needs a rebase though

…2822

bcardiff · 2018-06-09T17:10:35Z

@straight-shoota I rebase the changes already.

This was referenced Oct 15, 2017

Add custom time formats #5084

Closed

Add formatters and parsers for standard time formats #4729

Closed

Sija reviewed Oct 15, 2017

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straight-shoota force-pushed the jm-time-formats-simplified branch 2 times, most recently from ef5042d to 216efdb Compare October 15, 2017 11:00

straight-shoota mentioned this pull request Dec 14, 2017

Ensure time parser raises if timezone is missing #5382

Closed

straight-shoota force-pushed the jm-time-formats-simplified branch 4 times, most recently from 92e737f to be405fb Compare December 15, 2017 14:58

straight-shoota force-pushed the jm-time-formats-simplified branch from be405fb to a98da2a Compare December 15, 2017 16:34

straight-shoota force-pushed the jm-time-formats-simplified branch from a98da2a to 575f4eb Compare March 7, 2018 22:48

straight-shoota changed the title ~~Add custom time format implementations (simplified)~~ Add custom time format implementations Mar 7, 2018

straight-shoota force-pushed the jm-time-formats-simplified branch 3 times, most recently from 18fde5a to 1e1b76d Compare March 13, 2018 20:48

bcardiff reviewed Jun 5, 2018

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bcardiff added topic:stdlib breaking-change May have breaking effect in some edge cases. Mostly negligible, but still noteworthy. kind:feature labels Jun 5, 2018

straight-shoota force-pushed the jm-time-formats-simplified branch from 1e1b76d to 81cc01f Compare June 5, 2018 11:47

RX14 reviewed Jun 6, 2018

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straight-shoota force-pushed the jm-time-formats-simplified branch from e569afc to cb2e4fa Compare June 6, 2018 20:07

bcardiff approved these changes Jun 6, 2018

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RX14 requested changes Jun 7, 2018

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RX14 reviewed Jun 8, 2018

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RX14 approved these changes Jun 9, 2018

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straight-shoota added 8 commits June 9, 2018 18:39

Prepare: minor reorganization

5568528

Add custom format implementations for ISO 8601, RFC 3339, RFC 2822

e403e3c

Add formatter and parser class methods to Time for easier access

1794a7a

Add custom formatter for HTTP date format

b69bc43

fixup! Add custom formatter for HTTP date format

8d5dc10

fixup! Add custom formatter for HTTP date format

7cd3a52

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

db01f48

…2822

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

fee9ec4

…2822

bcardiff force-pushed the jm-time-formats-simplified branch from cb2e4fa to fee9ec4 Compare June 9, 2018 17:00

bcardiff merged commit 36647c8 into crystal-lang:master Jun 10, 2018

bcardiff added this to the 0.25.0 milestone Jun 10, 2018

straight-shoota deleted the jm-time-formats-simplified branch June 10, 2018 11:26

felixbuenemann mentioned this pull request Jun 16, 2018

Update to crystal 0.25.0 amberframework/amber#826

Closed

straight-shoota mentioned this pull request Aug 20, 2018

Fix Time::Format API doc #6578

Merged

jhass mentioned this pull request Feb 28, 2019

Default serialization of Time in JSON not RFC2822 nor ISO8601 compliant #7489

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