Cabal’s little helper provides access to build information gathered by
when configuring a project. Specifically we’re interested in retrieving enough
information to bring up a compiler session, using the GHC API, which is similar
cabal repl in a project.
While simple in principle this is complicated by the fact that the information Cabal writes to disk is in an unstable format and only really accessible through the Cabal API itself.
Since we do not want to bind the user of a development tool which utilises this library to a specific version of Cabal we compile the code which interfaces with the Cabal library’s API on the user’s machine, at runtime, against whichever version of Cabal was used to write the on disk information for a given project.
If this version of Cabal is not available on the users machine anymore, which is
fairly likely since cabal-install is usually linked statically, we have support
for compiling the Cabal library also. In this case the library is installed into
a private, isolated, package database in
$XDG_CACHE_HOME/cabal-helper so as to
not interfere with the user’s package database.
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