Use more deterministic distdir path in haskell_cabal_* #1648
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thufschmitt
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Use a path for distdir in the `haskell_cabal_*` rules that is based on the package name and deterministic unless there is a collision with an already existing file or directory. The distdir path enters flags that are passed to GHC and thereby enters the 'flag hash' field of the generated interface files. If the distdir path is indeterministic, then the interface file will also be indeterministic.
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Addresses indeterministic interface generation as reported in #1600.
Use a path for distdir in the
haskell_cabal_*rules that is based on the package name and deterministic unless there is a collision with an already existing file or directory.The distdir path enters flags that are passed to GHC and thereby enters the 'flag hash' field of the generated interface files. If the distdir path is indeterministic, then the interface file will also be indeterministic.
With this PR a build of the
hspecCabal library and its dependencies has been found to be bit-reproducible by building it twice without caching and comparing the outputs.Notably, there is still an issue with non-deterministic builds if a
haskell_cabal_*target has a C library dependency that was built by Bazel. In that case the absolute path to the sandbox execroot, which can change between builds, enters the include and library search path flags. Cabal forces us to provide these paths as absolute paths, see haskell/cabal#1317 and haskell/cabal#694. Meaning, the generated interface files ofhaskell_cabal_librarytargets with Bazel built C library dependencies remain indeterministic.