hsenv
hsenv is a tool (inspired by Python's virtualenv) to create isolated Haskell environments.
It creates a sandboxed environment in a .hsenv/ sub-directory
of your project, which, when activated, allows you to use regular Haskell tools
(ghc, ghci, ghc-pkg, cabal) to manage your Haskell code and environment.
It's possible to create an environment, that uses different GHC version
than your currently installed. Very simple emacs integration mode is included.
Basic usage
First, choose a directory where you want to keep your
sandboxed Haskell environment, usually a good choice is a directory containing
your cabalized project (if you want to work on a few projects
(perhaps an app and its dependent library), just choose any of them,
it doesn't really matter). Enter that directory:
Next, create your new isolated Haskell environment
(this is a one time only (per environment) step):
Now, every time you want to use this environment, you have to activate it:
That's it! Now it's possible to use all regular Haskell tools like usual,
but it won't affect your global/system's Haskell environment, and also
your per-user environment (from ~.cabal and ~.ghc) will stay the same.
All cabal-installed packages will be private to this environment,
and also the external environments (global and user) will not affect it
(this environment will only inherit very basic packages,
mostly ghc and Cabal and their deps).
When you're done working with this environment, enter command deactivate_hsenv,
or just close the current shell (with exit).
Named vs Unnamed Environments
By default, hsenv creates an "unnamed" environment, but sometimes for
particular use cases you might want to create different environments under
the same directory. This is achievable creating a "named" environment. To
do that, just pass the flag "--name=ENVIRONMENT_NAME" to hsenv:
hsenv --name=ENVIRONMENT_NAME
This will make hsenv to generate a folder of the form ".hsenv_ENVIRONMENT_NAME".
Advanced usage.
The only advanced usage is using different GHC version. This can be useful to test your code
against different GHC version (even against nightly builds).
First, download binary distribution of GHC for your platform
(e.g. ghc-7.0.4-i386-unknown-linux.tar.bz2), then create a new environment using that GHC
Then, proceed (with [de]activation) as in basic case.
Fetching and downloading a remote version of GHC
Recent versions of hsenv include the possibility to automatically download
and install a GHC version directly from the GHC main repository. To do that,
as regards the example above, all you need to do is to pass the desired version
of GHC you want to install:
Or a valid URL pointing to a compressed GHC archive:
Misc
hsenv has been tested on i386 Linux and FreeBSD systems,
but it should work on any Posix platform. External (from tarball) GHC feature
requires binary GHC distribution compiled for your platform,
that can be extracted with tar and installed with
"./configure --prefix=PATH; make install".
For more info please consult "hsenv --help" or the attached README file.
