Ulf Herrman <strin...@tilde.club> writes:
> [[PGP Signed Part:Undecided]] > #:deep? #t currently works by interposing a dummy build system that > lowers the package to a bag using the original build system, then > applies the supplied transformation to all of the bag's inputs, then > returns a new bag with the new inputs. > > The problem with this approach is that it doesn't affect the bag > arguments. This means that packages passed in as arguments may still > end up being used without being transformed. Worse still, packages > *not* passed in as arguments may end up being used *unless one is > explicitly passed in as an argument*, as is the case with > qt-build-system's #:qtbase argument. > > In short, the current approach of having the build-system lower > procedure leave the arguments mostly unchanged and letting the > bag->derivation procedure (the "bag builder") fill in lots of defaults > means that there are implicit inputs that cannot be touched at the > package level without adding special logic for every single build system > that does something like this. > > I propose that we have the build system lower procedure (that is, the > one that converts from package to bag) completely fill in the argument > list with all defaults, and we modify build-system-with-package-mapping > to transform all arguments that look like a package or a list of > packages (or maybe even a tree containing packages). > > Many large-scale package transformations have their purpose defeated if > even a single package slips through and has to be built or downloaded > separately (e.g. "I wanted to use a more minimal version of P, and now I > have both the original version of P *and* a more minimal version of P > *and* a duplicate copy of a large portion of the package graph..."). In > fact, in some situations, this could cause exponential growth of the > number of packages, e.g. a transformation is applied to qtbase and its > dependencies, but not to the implicit version and its dependencies, so > now all the dependencies of qtbase are duplicated, and if this happens > again at a higher level with something that depends on a package with > qt-build-system, now there are four duplicate subgraphs, and so on. > > What do you think? > > - Ulf > > [[End of PGP Signed Part]] Sounds like a good idea to me.
