This preprocessor splices in imports to the file you define it in. Haskell source files are discovered according to a glob relative to the file the code is defined in. This utility is useful when metaprogramming with a group of related files, where you want to use TemplateHaskell or similar

By default, the glob is for all modules in the directory containing the source file. Imports are qualified with the full module name to avoid potential import conflicts. The pre-processor will splice in a top-level value _importedModules :: [String] which contains the fully qualified names of the modules that were imported.

You may want to disable warnings for redundant imports, if you are only using type class information. A future option to the library may only do empty import lists, to only get access to type class instances.

As an example, consider the <https://hackage.haskell.org/package/persistent-discover persistent-discover> utility, which is inspired by hspec-discover. That utility will perform the following transformation:

-- srcPersistentModelsAll.hs

{-# OPTIONS_GHC -F -pgmF persistent-discover #-}

Then it will translate to:

-- srcPersistentModelsAll.hs

module PersistentModels.All where

import PersistentModels.Foo ()
import PersistentModels.Bar ()
import PersistentModels.Baz ()

allEntityDefs :: [EntityDef]
allEntityDefs = $(discoverEntities)

With this package, we can generalize the overall pattern. The new source module will look like this:

-- srcPersistentModelsAll.hs

{-# OPTIONS_GHC -F -pgmF glob-imports #-}

module PersistentModels.All where

import Database.Persist.Sql
{- GLOB_IMPORTS_SPLICE -}

allEntityDefs :: [EntityDef]
allEntityDefs = $(discoverEntities)

This preprocessor will convert this into this form:

-- srcPersistentModelsAll.hs

module PersistentModels.All where

import Database.Persist.Sql
import qualified PersistentModels.Foo
import qualified PersistentModels.Bar
import qualified PersistentModels.Baz

allEntityDefs :: [EntityDef]
allEntityDefs = $(discoverEntities)

Note how the only difference is that imports have been spliced in. This allows you to more flexibly customize how the code works.

Since: 0.1.0.0