Mailing-List: contact dev-help@groovy.apache.org; run by ezmlm
Precedence: bulk
Reply-To: dev@groovy.apache.org
MIME-Version: 1.0
In-Reply-To: <CADQzvmnPuVY4TAhJqriS2PUfLczAbW8-x5B+rXz0q1KXm2DVCg@mail.gmail.com>
References: <CADQzvmnPuVY4TAhJqriS2PUfLczAbW8-x5B+rXz0q1KXm2DVCg@mail.gmail.com>
Date: Mon, 2 May 2016 16:56:54 +0200
Message-ID: <CAJ2HCd-+k8QBjSwaLEmozXTMj_pgkai6gQpnrtBmABJa9ofDuw@mail.gmail.com>
Subject: Re: Automatic closure coercion and delegate
From: Guillaume Laforge <glaforge@gmail.com>
To: dev@groovy.apache.org
Content-Type: multipart/alternative; boundary=001a114b82701572a60531dd3482
archived-at: Mon, 02 May 2016 14:57:02 -0000

--001a114b82701572a60531dd3482
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: quoted-printable

+1

On Mon, May 2, 2016 at 4:44 PM, C=C3=A9dric Champeau <cedric.champeau@gmail=
.com>
wrote:

> Hi guys,
>
> I've been grumpy about this for a bit too long to keep it for myself, so
> let me explain the issue :)
>
> Imagine you have a Java method that accepts a SAM type:
>
> interface Action<T> {
>    void execute(T object)
> }
>
> class Person {
>     String name
> }
>
> void configure(Action<Person> config) {
>    config.execute(person)
> }
>
> then, you can call it in Groovy like this:
>
> configure {
>    it.name =3D 'Bob'
> }
>
> Whereas if we had a closure version, a nice and idiomatic way would be to
> write:
>
> configure {
>    name =3D 'Bob'
> }
>
> Note that in the `Action` version, we have to prefix everything with "it.=
".
>
> My wish is to make automatic closure coercion automatically set the
> delegate to the first argument, if available, and the delegation strategy
> to delegate first.
>
> Basically, it is important to integrate with Java 8 style SAM types and
> still benefit from a nicer Groovy DSL _without_ having to change the sour=
ce
> files. Typically, we don't have access to the JDK sources, so we have to
> write:
>
> def max =3D['Cedric','Jochen','Guillaume', 'Paul'].stream()
>   .mapToInt { it.length() }
>   .max()
>   .orElse(0)
>
> Where with this strategy we could use:
>
> def max =3D['Cedric','Jochen','Guillaume', 'Paul'].stream()
>   .mapToInt { length() }
>   .max()
>   .orElse(0)
>
> Of course, it may look a bit superficial but it is super important for
> nice DSLs like in Gradle. Typically, Gradle has a lot of domain objects
> that use the `Action<T>` interface above. Those actions allow the user to
> configure the domain objects typically from plugins written in Java (wher=
e
> you cannot use a closure). Since the `Closure` equivalent methods are
> always the same and that it's super simple to forget to implement one,
> Gradle chose to _not_ implement the `Closure` versions. Instead, they are
> generated at runtime, so the objects are decorated with one `Closure`
> method for each `Action` one.
>
> Unfortunately, this approach is defeated as soon as you want to use stati=
c
> compilation: then, you have no choice but implementing the `Closure`
> versions. This might be an option for Gradle (even though it would be ver=
y
> tedious), but not for all cases (we could also do this using extension
> methods, though, but really, you'd be doing this for _all_ domain objects=
).
> I think I could write a code generator that takes all java classes and
> generates an extension class with closure versions for all, also, but I'd
> like to know first what you think of this idea...
>
>


--=20
Guillaume Laforge
Apache Groovy committer & PMC Vice-President
Product Ninja & Advocate at Restlet <http://restlet.com>

Blog: http://glaforge.appspot.com/
Social: @glaforge <http://twitter.com/glaforge> / Google+
<https://plus.google.com/u/0/114130972232398734985/posts>

--001a114b82701572a60531dd3482
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr">+1</div><div class=3D"gmail_extra"><br><div class=3D"gmail=
_quote">On Mon, May 2, 2016 at 4:44 PM, C=C3=A9dric Champeau <span dir=3D"l=
tr">&lt;<a href=3D"mailto:cedric.champeau@gmail.com" target=3D"_blank">cedr=
ic.champeau@gmail.com</a>&gt;</span> wrote:<br><blockquote class=3D"gmail_q=
uote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1e=
x"><div dir=3D"ltr">Hi guys,<div><br></div><div>I&#39;ve been grumpy about =
this for a bit too long to keep it for myself, so let me explain the issue =
:)</div><div><br></div><div>Imagine you have a Java method that accepts a S=
AM type:</div><div><br></div><div>interface Action&lt;T&gt; {</div><div>=C2=
=A0 =C2=A0void execute(T object)</div><div>}</div><div><br></div><div>class=
 Person {</div><div>=C2=A0 =C2=A0 String name</div><div>}</div><div><br></d=
iv><div>void configure(Action&lt;Person&gt; config) {=C2=A0</div><div>=C2=
=A0 =C2=A0config.execute(person)</div><div>}</div><div><br></div><div>then,=
 you can call it in Groovy like this:</div><div><br></div><div>configure {<=
/div><div>=C2=A0 =C2=A0<a href=3D"http://it.name" target=3D"_blank">it.name=
</a> =3D &#39;Bob&#39;</div><div>}</div><div><br></div><div>Whereas if we h=
ad a closure version, a nice and idiomatic way would be to write:</div><div=
><br></div><div>configure {</div><div>=C2=A0 =C2=A0name =3D &#39;Bob&#39;</=
div><div>}</div><div><br></div><div>Note that in the `Action` version, we h=
ave to prefix everything with &quot;it.&quot;.</div><div><br></div><div>My =
wish is to make automatic closure coercion automatically set the delegate t=
o the first argument, if available, and the delegation strategy to delegate=
 first.</div><div><br></div><div>Basically, it is important to integrate wi=
th Java 8 style SAM types and still benefit from a nicer Groovy DSL _withou=
t_ having to change the source files. Typically, we don&#39;t have access t=
o the JDK sources, so we have to write:</div><div><br></div><div><div>def m=
ax =3D[&#39;Cedric&#39;,&#39;Jochen&#39;,&#39;Guillaume&#39;, &#39;Paul&#39=
;].stream()</div><div>=C2=A0 .mapToInt { it.length() }</div><div>=C2=A0 .ma=
x()</div><div>=C2=A0 .orElse(0)</div><div>=C2=A0=C2=A0</div></div><div>Wher=
e with this strategy we could use:</div><div><br></div><div><div>def max =
=3D[&#39;Cedric&#39;,&#39;Jochen&#39;,&#39;Guillaume&#39;, &#39;Paul&#39;].=
stream()</div><div>=C2=A0 .mapToInt { length() }</div><div>=C2=A0 .max()</d=
iv><div>=C2=A0 .orElse(0)</div><div>=C2=A0=C2=A0</div></div><div>Of course,=
 it may look a bit superficial but it is super important for nice DSLs like=
 in Gradle. Typically, Gradle has a lot of domain objects that use the `Act=
ion&lt;T&gt;` interface above. Those actions allow the user to configure th=
e domain objects typically from plugins written in Java (where you cannot u=
se a closure). Since the `Closure` equivalent methods are always the same a=
nd that it&#39;s super simple to forget to implement one, Gradle chose to _=
not_ implement the `Closure` versions. Instead, they are generated at runti=
me, so the objects are decorated with one `Closure` method for each `Action=
` one.</div><div><br></div><div>Unfortunately, this approach is defeated as=
 soon as you want to use static compilation: then, you have no choice but i=
mplementing the `Closure` versions. This might be an option for Gradle (eve=
n though it would be very tedious), but not for all cases (we could also do=
 this using extension methods, though, but really, you&#39;d be doing this =
for _all_ domain objects). I think I could write a code generator that take=
s all java classes and generates an extension class with closure versions f=
or all, also, but I&#39;d like to know first what you think of this idea...=
</div><div><br></div></div>
</blockquote></div><br><br clear=3D"all"><div><br></div>-- <br><div class=
=3D"gmail_signature"><div dir=3D"ltr"><div><div dir=3D"ltr"><div><div dir=
=3D"ltr"><div dir=3D"ltr"><div dir=3D"ltr">Guillaume Laforge<br>Apache Groo=
vy committer &amp; PMC Vice-President</div><div dir=3D"ltr">Product Ninja &=
amp; Advocate at <a href=3D"http://restlet.com" target=3D"_blank">Restlet</=
a><br><div><br></div><div>Blog:=C2=A0<a href=3D"http://glaforge.appspot.com=
/" target=3D"_blank">http://glaforge.appspot.com/</a><div><div>Social: <a h=
ref=3D"http://twitter.com/glaforge" target=3D"_blank">@glaforge</a>=C2=A0/ =
<a href=3D"https://plus.google.com/u/0/114130972232398734985/posts" target=
=3D"_blank">Google+</a></div></div></div></div></div></div></div></div></di=
v></div></div>
</div>

--001a114b82701572a60531dd3482--