build.d: simplify isUpToDate

[marler8997]

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[MoonlightSentinel]

Some suggestions

[MoonlightSentinel]

Maybe start with the timestamp of thisBuildScript to avoid the chain + array literal?

[marler8997]

This function is supposed to be generic, not specific to this particular build.d.

[MoonlightSentinel]

Okay

[PetarKirov]

BTW, we really ought to start using a more robust mechanism for determining whether we need to rebuild (like comparing a hash digest of the sources with a previously recorded hash, if any), not just the timestamp. Do you think this would be easily doable (of course I'm not talking about doing it with this PR)?

[marler8997]

"Source hashing" does make the build more robust, but comes at the cost of performance. @CyberShadow and I had a discussion about doing this in rund (dragon-lang/rund#22). Right now my thought is that source hashing for rund (and probably for build.d as well) is that it's not really worth the performance cost and extra build logic.

Note that I'm assuming that source hashing would only help with "false positives" (rebuilding when you don't need to). If it also fixes "false negatives" (not rebuilding when you do need to) then I would give it more importance. If you know of "false negative" use cases it would fix then let me know.

I think my comment here would also apply to source hashing in build.d: dragon-lang/rund#22 (comment)

[thewilsonator]

@marler8997 please give this a force push as it seems the doc tester has failed due to network errors.

[thewilsonator]

Oh, there a merge conflict.

[marler8997]

Rebased, this one should be good to go.