Default GHC flags with Haskell Stack

Question

I wanted to set some custom compiler flags for all stack-compiled packages on my machine (more aggressive optimizations than the defaults), and following the stack guide , I added some ghc-options (applying to "$everything" ) to my ~/.stack/config.yaml . These flags were properly applied to stack invocations outside of any project directory.

Within project directories, however, the stack.yaml options don't just take precedence; everything in ~/.stack/config.yaml is completely ignored! I have no ghc-options specified in any project-local stack.yaml files, but those specified ~/.stack/config.yaml have no effect.

The stack documentation would seem to suggest that options should collapse, as I had expected them to:

stack has two layers of configuration: project and non-project. All of these are stored in stack.yaml files, but the former has extra fields (resolver, packages, extra-deps, and flags). The latter can be monoidally combined so that a system config file provides defaults, which a user can override with ~/.stack/config.yaml, and a project can further customize.

Unless I have a very different idea of what "customize" means, this isn't the behavior I'm observing. Is there something I'm doing incorrectly, or is the documentation misleading in this respect?

Answer 1

Yup, I consider this to be a bug. I have a PR that hasn't been merged yet that fixes it https://github.com/commercialhaskell/stack/pull/3781