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From Paul King <pa...@asert.com.au>
Subject .with() variant that returns the original object
Date Tue, 08 Nov 2016 14:34:28 GMT
Hi everyone,

We are hoping to release 2.5 not too far down the track. We are
working on a revamped release process that is going to dramatically
improve our ability to release early/release often but also comply
with some additional Apache requirements that we follow these days.
But more on that another time.

One outstanding feature request targeted for potential inclusion in
2.5 is an alternative to .with{} that automatically returns the
original object after executing the closure - recall that .with{}
returns the last evaluated expression. The proposal is here:

https://github.com/apache/groovy/pull/174/files

We can't use the old name since that would break backward
compatibility and is of utility in its current form in any case, so we
are looking for a new name for the proposed method. If you look at the
PR you will see it has been called 'tap' and 'doto' and numerous other
names have been suggested. We regard naming as very important and
normally we'd have very strong views about suitable names based on
functionality and similar method names within the Groovy codebase. But
in this instance, an obvious name hasn't popped out at us, so we are
requesting feedback from the community about what names make most
sense to you.

Firstly, here is what the method does. I'll use 'tap' in these
examples since that is what the PR currently uses but we can easily
change that based on feedback.

myObject.tap {
    // some code
}

is equivalent to:

myObject.with {
    // some code
    return this
}

Returning the 'self' object lends itself to various kinds of chaining, e.g.

assert [:].tap {
    a = 1
}.tap {
    b = 2
} == [a:1, b:2]

Or this one (adapted from a blog post[1] - and assuming you have a
config.properties file containing answer=42 as one of the properties):

assert new Properties().tap {
    new FileInputStream('config.properties').withCloseable {
        load(it)
    }
}.answer == '42'

Here are some of the names that have been suggested with some commentary:

doto    Used by Clojure. Not camel case as per normal convention
(though we have upto and downto which also break that convention) and
it isn't immediately obvious which is which between with and doto just
from the names

tap    Comes from Ruby and a previous Groovy extension outside core
exists; meant to conjure up the idea of tapping into an object

autoWith    Same as with but automatically returns self

doWith   Again, hard to distinguish between doWith and with from the
names themselves

tee    An alternative name for tap

auto    A shortened version of 'autoWith'

apply    same as Kotlin which has copied Groovy's with but suffers
from the downside that apply is already heavily overleaded in other
contexts, e.g. functional programming

withThis    Distinction with normal with a bit subtle perhaps

asThis    Ditto

within    Ditto

I'll also point out the 'identity' is currently an alias for 'with',
in case that provides any additional inspiration.

Perhaps you dis/like one of the above or have some other suggestions.
Let us know.


Cheers, Paul.


[1] http://beust.com/weblog/2015/10/30/exploring-the-kotlin-standard-library/

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