RFR: 8260468: Wrong behavior of LocalDateTimeStringConverter

[Kevin Rushforth]

On Thu, 4 Feb 2021 20:01:10 GMT, Nir Lisker <nlisker at openjdk.org> wrote:

> Fixes a mutability issue for `LocalDateTimeStringConverter` (and `LocalDateStringConverter`) where the chronology can change during the lifetime of the instance and cause an inconsistent state. The following changes were made:
> 
> * The input is now formatted and parsed directly with the formatter and parser (which are configured with a chronology) without the chronology field value of the class.
> * The chronology field value does not change anymore when there is an exception due to inability to format the date.
> * Logging on failed formatting was removed as it did not seem useful. The formatter will throw the same exception that the chronology field does anyway, so there is not much use to catching the exception before hand.
> 
> Added a test that fails without this patch. The test creates a converter with an explicit `Chronology` and `null` parser and formatter. The default formatter that is created with the given chronology formats a legal date (with respect to the chronology) to a string, which the parser should be able to convert back to a date. However, by forcing an exception in the formatting process using an illegal date, the chronology changes, and now when the parser is used it is configured with the new chronology and it can't parse the string correctly.

The fix looks good to me, as does the test with a couple suggestions.

modules/javafx.base/src/test/java/test/javafx/util/converter/LocalDateTimeStringConverterTest.java line 167:

> 165:         // force a chronology change with an invalid Japanese date
> 166:         try {
> 167:             System.out.println(converter.toString(LocalDateTime.of(1, 1, 1, 1, 1, 1)));

Since you are expecting an exception, it seems a good idea to fail if you didn't get one. Something like:
    fail("Did not get the expected exception");
Also, you might consider narrowing the `catch` to just the exception that you expect, so that an unexpected exception will also fail the test.

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PR: https://git.openjdk.java.net/jfx/pull/393