Prevent stack from recompiling external dependencies

[callmeyesh]

I am relatively new to stack and I wasn't able to figure out if this feature already exists. Before I explain my question, let me explain our development setup. We use jenkins to build our repo. The haskell project will be a small subset of a larger python project. The haskell project is mainly used to generate artifacts.

The jenkins master does a git clean each time before building a git branch. My haskell project has some external dependency like argparser & aeson. Each time my build scripts execute a stack build, these external dependencies get compiled because they are deleted when jenkins executes the git clean command.

Is there anyway to tell stack to download the external deps to a global folder outside the project folder? Like the global-pkg-db path instead of the .stack-work folder? What is the best way to prevent stack from recompile the external dependencies?

This is my stack.yaml file:

# This file was automatically generated by stack init
# For more information, see: http://docs.haskellstack.org/en/stable/yaml_configuration/

# Specifies the GHC version and set of packages available (e.g., lts-3.5, nightly-2015-09-21, ghc-7.10.2)
resolver: lts-5.8

# Local packages, usually specified by relative directory name
packages:
- '.'
# Packages to be pulled from upstream that are not in the resolver (e.g., acme-missiles-0.3)
extra-deps:
- aeson-0.11.1.1
- argparser-0.3.4
- text-1.2.2.0

# Override default flag values for local packages and extra-deps
flags: {}

# Extra package databases containing global packages
extra-package-dbs: []

[mgsloan]

By having extra-deps versions of aeson and text, anything that depends on them (many packages) will be built and compiled to your local project directory. This may be resolved by #1265, which will hopefully happen soonish.

[callmeyesh]

Awesome, that will improve the compilation time. Is there anyway to specify the location where the extra-deps will get compiled?

[mgsloan]

You can change the work-dir location, but due to the intersection of various issues, it isn't as flexible as we'd like: #1731

Once extra-deps are compiled to something like a snapshot, those dependencies will be outside of your project dir.