Disable benchmarks and tests for tools

[hamishmack]

By default haskell.nix cabalProject functions run cabal
configure with --enable-tests and --enable-benchmarks.
This is good when you are working on a project as
it means your tests and benchmarks are in the
package components.

The tools functions (and shellFor tools arg)
return components.exes.${toolName} and while
it is possible to access the other components
via the project and package properties of
tool component.

In some cases the benchmarks and tests can
have problematic constraints that cause
problems building other components.

Disabling the tests and benchmarks by default
when building tools should reduce the these
issues.

[michaelpj]

Makes sense to me.

A possible heuristic that occurs to me: what happens if you do cabal install foo to tell cabal to install an executable? Does it build it with benchmarks and tests enabled? Could we have the property that tool does ~= what cabal install does?

[hamishmack]

bors try

[iohk-bors]

try

Build succeeded:

• buildkite/haskell-dot-nix
• ci/hydra:Cardano:haskell-nix:required

[hamishmack]

cabal configure defaults to tests and benchmarks disabled. Having configureArgs default to "--enable-tests --enable-benchmarks" is something cabalProject does.

Switching from running cabal install and cabal test causes a new plan.json to be created (with or without the tests). If you try to cabal install a test you get an error like this:

[nix-shell:~/iohk/haskell-language-server]$ cabal install test:func-test
cabal: Cannot build the test suite 'func-test' because building test suites
has been explicitly disabled in the configuration. You can adjust this
configuration in the cabal.project{.local} file either for all packages in the
project or on a per-package basis. Note that if you do not explicitly disable
test suites then the solver will merely try to make a plan with them
available, so you may wish to explicitly enable them which will require the
solver to find a plan with them available or to fail with an explanation.