forked from lix-project/lix
37fca662b0
In https://github.com/NixOS/nix/pull/6311#discussion_r834863823, I realized since derivation goals' wanted outputs can "grow" due to overlapping dependencies (See `DerivationGoal::addWantedOutputs`, called by `Worker::makeDerivationGoalCommon`), the previous bug fix had an unfortunate side effect of causing more pointless rebuilds. In paticular, we have this situation: 1. Goal made from `DerivedPath::Built { foo, {a} }`. 2. Goal gives on on substituting, starts building. 3. Goal made from `DerivedPath::Built { foo, {b} }`, in fact is just modified original goal. 4. Though the goal had gotten as far as building, so all outputs were going to be produced, `addWantedOutputs` no longer knows that and so the goal is flagged to be restarted. This might sound far-fetched with input-addressed drvs, where we usually basically have all our goals "planned out" before we start doing anything, but with CA derivation goals and especially RFC 92, where *drv resolution* means goals are created after some building is completed, it is more likely to happen. So the first thing to do was restore the clearing of `wantedOutputs` we used to do, and then filter the outputs in `buildPathsWithResults` to only get the ones we care about. But fix also has its own side effect in that the `DerivedPath` in the `BuildResult` in `DerivationGoal` cannot be trusted; it is merely the *first* `DerivedPath` for which this goal was originally created. To remedy this, I made `BuildResult` be like it was before, and instead made `KeyedBuildResult` be a subclass wit the path. Only `buildPathsWithResults` returns `KeyedBuildResult`s, everything else just becomes like it was before, where the "key" is unambiguous from context. I think separating the "primary key" field(s) from the other fields is good practical in general anyways. (I would like to do the same thing for `ValidPathInfo`.) Among other things, it allows constructions like `std::map<Key, ThingWithKey>` where doesn't contain duplicate keys and just precludes the possibility of those duplicate keys being out of sync. We might leverage the above someday to overload `buildPathsWithResults` to take a *set* of return a *map* per the above. ----- Unfortunately, we need to avoid C++20 strictness on designated initializers. (BTW https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2021/p2287r1.html this offers some new syntax for this use-case. Hopefully this will be adopted and we can eventually use it.) No having that yet, maybe it would be better to not make `KeyedBuildResult` a subclass to just avoid this. Co-authored-by: Robert Hensing <roberth@users.noreply.github.com> |
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| .. | ||
| build-remote | ||
| libcmd | ||
| libexpr | ||
| libfetchers | ||
| libmain | ||
| libstore | ||
| libutil | ||
| nix | ||
| nix-build | ||
| nix-channel | ||
| nix-collect-garbage | ||
| nix-copy-closure | ||
| nix-env | ||
| nix-instantiate | ||
| nix-store | ||
| resolve-system-dependencies | ||
| toml11 | ||