Issue2558

This is not a bug, but i wasn't sure where to put improvements? It would be nice if when calling a java method which takes a enum automatic type conversion from string could be done if possible. This would make calling enum methods more convenient.

At the moment a call to a method taking a enum with a string fails, even if the enum valueOf(String) method would work e.g

Jython 2.7.1b3 (, Feb 28 2017, 19:53:14) 
[Java HotSpot(TM) 64-Bit Server VM (Oracle Corporation)] on java1.8.0_121
Type "help", "copyright", "credits" or "license" for more information.
>>> import java.time.LocalDate
>>> date = java.time.LocalDate.of(2015, 'DECEMBER', 3)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: of(): 2nd arg can't be coerced to int, java.time.Month
>>> 

Since Jython already does other similar type coercion I think this would be a nice extension, but maybe i'm missing a reason why its a really bad idea?

I have a pull request which can enable this https://github.com/jythontools/jython/pull/58

After this change the behaviour is

Jython 2.7.1b3 (, Feb 28 2017, 19:05:08) 
[Java HotSpot(TM) 64-Bit Server VM (Oracle Corporation)] on java1.8.0_121
Type "help", "copyright", "credits" or "license" for more information.
>>> import java.time.LocalDate
>>> date = java.time.LocalDate.of(2015, 'DECEMBER', 3)
>>> date
2015-12-03
>>> date.getMonth().__class__
<type 'java.time.Month'>
>>> 

Where 'DECEMBER' is automatically coerced into java.time.Month.DECEMBER

I would be interested in what people think of this idea?

I am actually much for improving Java integration, but IMO Strings and Enums are quite not the same (and don't even share an is-relation in any direction). Looking at https://docs.oracle.com/javase/tutorial/java/javaOO/enum.html an Enum can also be a Planet etc, have custom properties, even methods.

Note that enumMethod in your test also wouldn't accept a String when called in Java-code.

You suggest to let Jython convert silently a String in the role of an element name into a value of Enum subtype. For me this looks like mixing up something like a lookup (e.g. in a map) with an is-relation. Or stated differently: Too much magic, even for Jython users.

That said, I would like to have a proper way to allow the method call you mention (maybe there already is?)
E.g. something like an explicit (is better than implicit...^^) way to let Jython perform Enum-lookup from Python-code.
Maybe we could have an integration with the official Python module for enums https://pypi.python.org/pypi/enum34 (for Python 3, but also backported to several Python 2 versions).

I will think about it and would also wish to hear more opinions.

I think automatic coercion of a string would turn out badly: we'll discover cases where two signatures match. Compare the insoluble #1781.

We can do this:
>>> import java.time.LocalDate
>>> from java.time import Month
>>> java.time.LocalDate.of(2015, Month.DECEMBER, 3)
2015-12-03

or:
>>> from java.time.Month import *
>>> DECEMBER
DECEMBER
>>> java.time.LocalDate.of(2015, DECEMBER, 3)
2015-12-03

Does that not do the trick?

Yes there are lots of better solutions than what is proposed here which is almost certainly a bad idea.

This should be closed as won't implement.

Thanks James. Looking at GitHub, I see you had second thoughts (and third) nearly a year ago.