BSD-3-Clause licensed by Matt Parsons
Maintained by [email protected]
This version can be pinned in stack with:persistent-discover-,3646

Module documentation for


build status

Supports automatic discovery of your persistent models.

As an executable

Let’s say you’ve got a ton of persistent database models, all defined in a module hierarchy like this:


If you’re using persistent to automatically generate migrations, you’ll want to have all the [EntityDef] in scope from each module. You can do that by importing each module that defines models and calling $(discoverEntities), introduced in persistent-2.13.

But you may forget to import a module.

This utility imports all the modules defined in the current directory and sub-directories, and then it calls $(discoverEntities) for you.

To use it, place the following command in a file, located in the same directory that your Haskell modules are in:

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

Let’s say we put that in src/Models/All.hs. This generates a module Models.All that exports a single item: allEntities, which is a [EntityDef] and can be used by migrateModels to properly perform migrations.

You’ll need to add persistent-discover to the build-tool-depends on your cabal file for this to work.


Changelog for persistent-discover

Unreleased changes

  • Support mtl-2.3 #9

  • Support GHC 9.4 #7

  • Fix a bug where TemplateHaskell pragma was not added. #6

  • Fix a bug where non-Haskell files would be picked up and imported in the generated file. #4

  • Remove embarrasing lib module.

  • Support GHC 9 #3

  • Fix behavior where uppercase directories (eg on Mac OS) would cause incorrect module names. #2

  • Initial Release