configureCompiler: separate compiler vs ProgramDb #10993
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sheaf
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Jun 17, 2025
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| -- Now, **outside** of the caching logic of 'rerunIfChanged', add on | ||
| -- auxiliary unconfigured programs to the ProgramDb (e.g. hc-pkg, haddock, ar, ld...). | ||
| -- | ||
| -- See Note [Caching the result of configuring the compiler] | ||
| finalProgDb <- liftIO $ Cabal.configCompilerProgDb verbosity hc hcProgDb hcPkg | ||
| return (hc, plat, finalProgDb) |
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This is the main change: we move out the logic for finding ar, ld etc outside of the recompilation logic. This is because they will typically remain as unconfigured programs until they are needed, which means they would be silently dropped when reloading from cache due to the lossiness of the Binary ProgramDb instance when unconfigured programs are involved.
mpickering
approved these changes
Jun 17, 2025
geekosaur
approved these changes
Jun 17, 2025
This commit splits up the logic in configureCompiler into two parts:
1. Configuring the compiler proper, e.g. finding the location
and version of GHC.
2. Creating a program database of attendant programs such as ghc-pkg,
haddock, and build tools such as ar, ld.
This is done using information about the compiler, such as its
location on the filesystem and toolchain information from its
settings file.
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I will not be providing a test for this change, as I think the prior hacky solution was "good enough" to solve the issue with recompilation-checking. I discussed the design with @mpickering and I think the new approach makes a lot more sense than what was there before. |
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This commit splits up the logic in configureCompiler into two parts:
ghc-pkg,haddock, and build tools such asar,ld. This is done using information about the compiler, such as its location on the filesystem and toolchain information from its settings file.The main goal is to avoid an issue in which we get the wrong program database from the cache we get from recompilation checking. However, it's not straightforward to trigger the bug, so I don't have a test at the moment. In practice, I expect this change to be invisible to users.
See Note [Caching the result of configuring the compiler] for an explanation of the problem and the design of the solution.
Template B: This PR does not modify behaviour or interface
E.g. the PR only touches documentation or tests, does refactorings, etc.
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