8364752: Class java.time.Instant cannot parse all ISO 8601 date formats

[naotoj]

Instant.parse() is expected to use the offset zone pattern +HH:mm:ss (as defined by DateTimeFormatterBuilder.appendOffsetId()), but it fails to parse hour-only offsets such as +02. This is because the actual implementation uses +HH:MM:ss as the pattern. While replacing the pattern in the implementation as with the specification would allow hour-only offsets, it would also introduce compatibility issues, i.e., printing would omit the minutes field when it is zero. So, it is preferable to update the specification to match the implementation. A CSR has also been drafted for this change.

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• Change requires CSR request JDK-8365182 to be approved

Issues

• JDK-8364752: Class java.time.Instant cannot parse all ISO 8601 date formats (Bug - P3)
• JDK-8365182: Class java.time.Instant cannot parse all ISO 8601 date formats (CSR)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/26708/head:pull/26708
$ git checkout pull/26708

Update a local copy of the PR:
$ git checkout pull/26708
$ git pull https://git.openjdk.org/jdk.git pull/26708/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 26708

View PR using the GUI difftool:
$ git pr show -t 26708

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/26708.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back naoto! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[openjdk]

@naotoj The following labels will be automatically applied to this pull request:

• core-libs
• i18n

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing lists. If you would like to change these labels, use the /label pull request command.

[mlbridge]

Webrevs

• 00: Full (7fc267a3)

[ExE-Boss]

How about using different patterns for parsing and printing instead?

[vy]

Shall we accompany the changes with a set of tests that verifies java.time.Instant::parse against all all ISO 8601 date formats?

[naotoj]

How about using different patterns for parsing and printing instead?

In fact, the current DateTimeFormatterBuilder.InstantPrinterParser already use different behavior for formatting, i.e., only print time in "Z" (no offset).

The following change:

--- a/src/java.base/share/classes/java/time/format/DateTimeFormatterBuilder.java
+++ b/src/java.base/share/classes/java/time/format/DateTimeFormatterBuilder.java
@@ -3887,7 +3887,7 @@ public int parse(DateTimeParseContext context, CharSequence text, int position)
                     .appendValue(MINUTE_OF_HOUR, 2).appendLiteral(':')
                     .appendValue(SECOND_OF_MINUTE, 2)
                     .appendFraction(NANO_OF_SECOND, minDigits, maxDigits, true)
-                    .appendOffsetId()
+                    .appendOffset("+HH:mm:ss", "Z")
                     .toFormatter().toPrinterParser(false);
             DateTimeParseContext newContext = context.copy();
             int pos = parser.parse(newContext, text, position);

will parse hour-only offset for Instant.parse() but I am not sure we would go for this, as other ISO formatters all use "MM" for minutes. @jodastephen any suggestions?

[naotoj]

Shall we accompany the changes with a set of tests that verifies java.time.Instant::parse against all all ISO 8601 date formats?

I don't think Instant.parse() allows all permitted zone offset styles in ISO, only allowing "+HH:MM:ss" in strict mode. If the user wants to allow all of the format, they would be able to create a custom formatter in lenient mode and use the pattern "+HH" for offset parsing.