utils/ghc-pkg/Main.hs¶
Note [Recompute abi-depends]¶
Like most fields, ghc-pkg relies on who-ever is performing package registration to fill in fields; this includes the abi-depends field present for the package.
However, this was likely a mistake, and is not very robust; in certain cases, versions of Cabal may use bogus abi-depends fields for a package when doing builds. Why? Because package database information is aggressively cached; it is possible to work Cabal into a situation where it uses a cached version of abi-depends, rather than the one in the actual database after it has been recomputed.
However, there is an easy fix: ghc-pkg /already/ knows the abi-depends of a package, because they are the ABIs of the packages pointed at by the depends field. So it can simply look up the abi from the dependencies in the original database, and ignore whatever the system registering gave it.
So, instead, we do two things here:
- We throw away the information for a registered package’s abi-depends field.
- We recompute it: we simply look up the unit ID of the package in the original database, and use its abi-depends.
See #14381, and Cabal issue #4728.
Additionally, because we are throwing away the original (declared) ABI deps, we return a boolean that indicates whether any abi-depends were actually overridden.
