On 2016-02-18 at 13:32:59 +0100, Andrey Mokhov wrote: [...]
Interesting! In the new Shake-based build system we also need to automagically generate .hs files using Alex et al. My first implementation was slow but then I realised that it is possible to scan the source tree only once and remember where all .hs/.x/etc files are. This brought down the complexity from quadratic to linear in my case -- maybe this could be reused in cabal too?
This sounds very risky; are you suggesting to blindly traverse the hs-src-dirs *before* you even know what is searched for? If so, this will cause problems; we're already seeing problems with this in the cabal nix-local-branch, which currently (it's a bug) recursively traverses the project folder for computing a source-hash over content that would not even make it into the source-dist... There must be a better way to solve this...