Modify the GHC_ENVIRONMENT env var in Stack.Setup #4715
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This fixes #4706. Since GHC 8.0, GHC will now implicitly read in from a .ghc.environment.* file, which can cause commands like `stack exec ghci` to fail. Due to the use case of `stack exec`, it doesn't make sense to try to create our own environment file, but instead tell GHC to ignore it. Unfortunately, the ability to ignore environment files was only added in GHC 8.4.4. This patch: * Unsets any `GHC_ENVIRONMENT` variable already set outside of Stack * When using GHC 8.4.4 or later, sets the variable to `-` This will help work around situations where `cabal new-build` creates an environment file without the user's awareness. This may be somewhat superfluous in the future depending on changes to either GHC or cabal-install, but shouldn't present any harm for the foreseeable future (unless GHC changes its understanding of `GHC_ENVIRONMENT`).
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CC @phadej @tfausak
This fixes #4706. Since GHC 8.0, GHC will now implicitly read in from a
.ghc.environment.* file, which can cause commands like
stack exec ghcito fail. Due to the use case of
stack exec, it doesn't make sense totry to create our own environment file, but instead tell GHC to ignore
it. Unfortunately, the ability to ignore environment files was only
added in GHC 8.4.4. This patch:
GHC_ENVIRONMENTvariable already set outside of Stack-This will help work around situations where
cabal new-buildcreates anenvironment file without the user's awareness. This may be somewhat
superfluous in the future depending on changes to either GHC or
cabal-install, but shouldn't present any harm for the foreseeable future
(unless GHC changes its understanding of
GHC_ENVIRONMENT).Note: Documentation fixes for https://docs.haskellstack.org/en/stable/ should target the "stable" branch, not master.
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Please also shortly describe how you tested your change. Bonus points for added tests!