On 9/18/16 8:14 AM, Andrei Alexandrescu wrote:
> On 9/18/16 6:00 AM, Jonathan M Davis via Digitalmars-d wrote:
>> Yes. That's DIP 82:
>>
>> http://wiki.dlang.org/DIP82
>>
>> I need to go over it again and then introduce it into the new DIP
>> process.
>> But I really think that that's where we should go to fix this problem.
>
> Just a thought: things that we can't do have high priority. Things that
> we can do with a modest cost are much less attractive. Consider:
>
> struct Awesome(A, B, C)
> {
>     private enum ut = is(A == int) && is(B == int) && is(C == int);
>
>     static if (ut) unittest
>     {
>         ...
>     }
> }
>
> You're looking at an overhead with a small fixed cost plus a few
> characters ("if (ut)") per unittest.

This is exactly how I did RedBlackTree unit tests:

https://github.com/dlang/phobos/blob/master/std/container/rbtree.d#L748
https://github.com/dlang/phobos/blob/master/std/container/rbtree.d#L815

This is still less than ideal, and has caused some real problems over the years. e.g.:

https://issues.dlang.org/show_bug.cgi?id=12246
https://issues.dlang.org/show_bug.cgi?id=14082

The best solution IMO is not to run templated unit tests unless specifically requested. Perhaps only run them when instantiated inside a unittest block?

All that being said, running unit tests on EVERY integral type caught about 3 bugs in the compiler when I was creating dcollections, and found several corner-case bugs in my code as well. It was well worth the "overhead" IMO.

-Steve

On Sat, Sep 17, 2016 at 01:22:52PM -0400, Andrei Alexandrescu via Digitalmars-d wrote:
> Recall the discussion a few days ago about unittests inside templates being instantiated with the template. Often that's desirable, but sometimes not - for example when you want to generate nice ddoc unittests and avoid bloating. For those cases, here's a simple solution that I don't think has been mentioned:

I've already mentioned this exact idea recently in the d-learn forum. Nobody responded then.


> /** Awesome struct */
> struct Awesome(T)
> {
>     /** Awesome function. */
>     void awesome() {}
> 
>     ///
>     static if (is(T == int)) unittest
>     {
>         Awesome awesome;
>         awesome.awesome;
>     }
> }
> 
> The unittest documentation is nicely generated. The unittest code itself is only generated for one instantiation.
[...]

And you also have to make sure Awesome!int is actually instantiated, otherwise the unittest won't actually run!


T

-- 
In theory, there is no difference between theory and practice.

On Mon, Sep 19, 2016 at 09:02:05AM -0700, H. S. Teoh via Digitalmars-d wrote:
> On Sat, Sep 17, 2016 at 01:22:52PM -0400, Andrei Alexandrescu via Digitalmars-d wrote:
> > Recall the discussion a few days ago about unittests inside templates being instantiated with the template. Often that's desirable, but sometimes not - for example when you want to generate nice ddoc unittests and avoid bloating. For those cases, here's a simple solution that I don't think has been mentioned:
> 
> I've already mentioned this exact idea recently in the d-learn forum. Nobody responded then.
[...]

Correction: it was on this very same forum:

	http://forum.dlang.org/post/mailman.96.1472754654.2965.digitalmars-d@puremagic.com


T

-- 
May you live all the days of your life. -- Jonathan Swift

On Sunday, 18 September 2016 at 12:16:54 UTC, Andrei Alexandrescu wrote:
> I don't see that as much of a hurdle seeing as any template written has a few "obvious" types it'll work with. To encapsulate that if needed:
>
> struct Awesome(A, B, C)
> {
>     private enum ut = is(A == int) && is(B == int) && is(C == int);
>     unittest { alias Awe = Awesome!(int, int, int); }
>
>     static if (ut) unittest
>     {
>         ...
>     }
> }

I like how the non-static unittest ensures that any instantiation of Awesome triggers the static unittest. I've encapsulated this pattern into a template:

https://github.com/ntrel/stuff/blob/master/testinstanceflag.d#L34

Awesome would then just need one line instead of two before the 'static if' line:

private enum ut = testInstanceFlag!(Awesome, int, int, int);

(testInstanceFlag currently only works with one argument though). The nice thing is that people reading the source can look up the docs for testInstanceFlag to learn about it.