[Silhouette]

If you have some developer that wants to write something in a new (for your company) language, or even worse goes off and does so without asking, because he wants to try it out, you probably want to fire that guy. Either he doesn't understand the downsides or he does, but doesn't care.

What if it has the potential to be a much better tool for the job than the mainstream options, and your developer thinks it's worth trying it to find out?

I've seen this situation with adopting a relatively unusual language for a task that needed particularly high reliability. Yes, it was a concern that only one person currently working in the organisation knew much about it and that it might be harder to hire help if more developers were required later. On the other hand, that software was developed faster than the similar system it was due to supersede, and it had a much lower rate of reported bugs once deployed.

Of course you don't want to hire people who intend to pad their resumes with extra buzzwords on your dollar when it has no business benefit, but equally, if you never use tools that aren't chosen from among a small set of mainstream options, you'll never outperform what you can do with mainstream tools.

[pjmlp]

Software development is much more than just programming languages, I have seen teams outperform with lousy languages thanks to a great team spirit and understanding of customer needs.

[Silhouette]

For sure. A good craftsman will do good work with any reasonable set of tools.

They'll still achieve their best possible results and performance with high quality tools of their own choosing, though.

[bradleyjg]

I guess my answer would be that this is the kind of decision that requires being able to see the big picture. Is an individual developer in a position to weigh future recruitment challenges?

My remark about firing a person merely wanting to write something in a different language was off base and end up derailing the discussion. But the point I should have made, and stick by, is that this decision is properly made at either the company wide level, or for large companies at the level several rungs up the ladder. It isn't at all, like someone suggested above, equivalent to picking a personal IDE.

[Silhouette]

Is an individual developer in a position to weigh future recruitment challenges?

Maybe, particularly if it's a smaller organisation.

In any case, it's obviously a management decision at some point, as all things are. However, it seems quite reasonable for me for a developer to advocate using a more suitable tool even if it's not an existing choice/standard within the organisation, and if they make a good case, it seems quite reasonable to me that management might then back them despite the downsides if the upsides appear greater.