Possible to build test dependencies without running tests?

[dkubb]

I am using stack with CircleCI, and I'd like a way to build the test dependencies up-front without actually running the tests. With CircleCI I am caching the build output so that repeated runs are done more quickly. Here is what I am doing:

Setup:

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys C5705533DA4F78D8664B5DC0575159689BEFB442
echo 'deb http://download.fpcomplete.com/ubuntu/precise stable main' | sudo tee /etc/apt/sources.list.d/fpco.list
sudo apt-get update
sudo apt-get install stack -y

Build:

# A snapshot of .stack-work and ~/.stack is restored from a previous run (if any)

stack build --no-terminal --install-ghc --jobs 2
stack test --prefetch --dry-run

# A snapshot of .stack-work and ~/.stack is persisted

Test:

stack test

The problem is the stack test still goes through a lengthy build process. I would love to be able to do this in the build phase rather than when the tests run.

Also if there's anything else I could improve in my stack usage please let me know.

[DanBurton]

👍 great feature request, not sure if we have it yet.

[dkubb]

Originally my assumption was that stack build would just build all dependencies by default. I was surprised when it didn't.

In the meantime I hacked together something ugly that does compile all the test dependencies:

stack test --prefetch --dry-run \
  | sed -e '1,/^Would build:/d' -e '/^Would test:/,$d' \
  | cut -d":" -f1 \
  | xargs -I{} stack build {} --no-terminal --jobs 2

It seems to work, but is obviously brittle since it will break if the prefetch output changes even slightly.

[snoyberg]

That's what we added the --only-snapshot flag for. Check out #387 and #310

[snoyberg]

I'm going to close this as unnecessary based on the --only-snapshot flag. If there's some issue with this, let's discuss (probably in #387).