[Nix-dev] Improving the Developer Experience in the Nix Community

[Michael Raskin]

>> Many webapps will need to specify that "a" database library is present, but may not care which one.
>Heh: if the web app is so "careless" to not specify which database to use,
>there's no reason why other system components should care about a busted web app.

The point is: sometimes it can use whatever is available without 
rebuild, so why not let user test various options faster?

>> > - There is a simple way to derive a version of package with dependency
>> > versions changed (for use with subsituters, mainly)
>> Can you expand on this here? How would such a feature help?
>> Should I have to recompile all my *.jar files just because I upgraded my runtime environment? I hope the answer is no! :)
>The answer  depends on whether your runtime environment upgrade just broke your jar files.

Oh, let me create a new path with substituted dependencies and check 
quickly!

And if it doesn't break, I still save time w.r.t. a full rebuild.

>> > - There is a way to replace subsituted package with a "better"
>> > substitution or native build
>> Continuing with a Java theme: the Java Advanced Imaging interfaces have a (default) pure java implementation as well as a native (accelerated) implementation.
>If two application choices  are equivalent, then there is no basis for choice and either suffices.
>Coin flipping is as logical as any other choosing: revisit the meaning of "equivalent" if you don't
>like what the coin sez.

Why not package easier-to-build way, check that a few applications build
against it and work, spend more effort building native faster library 
and be able to try out the same apps without a long rebuild?

You are not losing anything, after all.

Afterwards, you will be able to ask for a honest rebuild instead of 
substitution and after it turns out that this works OK, you will replace
substituted path with a natively built one.