[Haskell-cafe] ANNOUNCE: module-management-0.9.3 - clean import lists, split and merge modules

[David Fox]

Thanks, great feedback, clearly I've been too close to this to see
what people need to know.  Let me give some answers, and they I will
integrate them into the documentation.

On Thu, Jun 27, 2013 at 6:06 PM, Marc Weber <marco-oweber at gmx.de> wrote:
> let me give you an example:
>
>   splitModule :: MonadClean m => ModuleName -> m ()
>
>   Split each of a module's declarations into a new module. Update the
>   imports of all the modules in the moduVerse to reflect the split.
>
> Why do I want that? What does it mean?

Split and merge were the simplest set of operations that would allow
you build more complex operations like move a symbol from one module
to another.  Directly implementing more complex for reasons that I
could discuss later.  It may be desirable to provide compound
operations like move symbol implemented in terms of split and merge.

>
> === start file ==
>   module Start where
>
>   a = 1
>   b = 2
>   c = 3
>
> will calling that function yield
>
>   module foobar where
>   a = 1
>
>   module baz.something.idont.know where
>   b =2
>
>   module 3rd where
>   c =3
>
> I want to say: I have no idea
>   - how the new modules will be named
>   - which paths the new modules will have

Yes, you will get three modules each containing the declarations of a
single symbol.  The modules are placed in a sub-directory of the
original module, and the names are constructed from the symbol names.
So you will get modules Start.A, Start.B and Start.C.  If there are
non-alphanumeric characters in the symbol they are removed, and the
first character is capitalized.  If more than one symbol maps to the
same module name a single module is created containing both.  If no
module name can be constructed the symbol goes into
Start.OtherSymbols.

Instances go into a module named Start.Instances.  Symbols that were
just imported and re-exported from Start go into Start.ReExported.
Symbols that were not exported from Start go into the subdirectory
Internal, so if 'a' was not exported it would go into
Start.Internal.A.

>
> Function's return type is m (), so doesn't help much.
>
> Consider improving that documentation.
>
> More questions: input/output.
>
>   findPaths "Language" >>= runMonadClean . mapM cleanImports . toList
>
> Whose task is it to write the "new cleaned up module" to disk again?
> does runMonadClean do it for me? Docs don't tell yet.
>
> Marc Weber

The cleanImports function is the one that computes the new file
contents and does the IO.  The runMonadClean function sets up the
environment for cleanImports to run, if you wanted to chain a series
of clean/split/merge operations together you would do it in a single
runMonadClean operation so that the set of modules that need to be
checked and updated can be tracked.

runCleanT would probably be a better name.