Certain module prefixes, e.g. `Data`, can only import outside your codebase

elm-package install choonkeat/only-import-outside 1.0.0



Enforces that certain module prefixes, e.g. Data, can only import modules from outside your codebase

Base scenario

Any module in our codebase can import from Data.* modules in your codebase

module Page exposing (Page)

import Data.Animal
import Data.Thing.Gadget

But ideally, code written in src/Data/**/*.elm and src/Data.elm cannot import from other modules in the codebase, including other Data.* modules (except if they are "parent-child" modules, e.g. Data.Animal and Data.Animal.Dog)

Quick trial

to check against your src/Data using this rule

npx elm-review --template choonkeat/only-import-outside/example/review

if you're happy with that (or you don't have a src/Data to try against), then proceed below to install and setup


First, setup elm-review if you haven't

npx elm-review init

Install this package inside ./review sub directory

cd review
elm install choonkeat/only-import-outside

add a OnlyImportOutside.rule to your config

module ReviewConfig exposing (config)

import OnlyImportOutside
import Review.Rule exposing (Rule)

config : List Rule
config =
    [ OnlyImportOutside.rule
        { constrainedModulePrefixes = [ "Data" ]
        , allowedModulePrefixes = [ "Extra" ] -- for illustration only; you can leave it `[]`

Acceptable module imports

module Data.Animal.Dog exposing (Dog)

import Data.Animal

Acceptable since it's importing parent module (in terms of directory hierarchy)

module Data.Thing exposing (Thing)

import Data.Thing.Gadget

Acceptable since it's importing child module (in terms of directory hierarchy)

module Data.Thing exposing (Thing)

import Extra.Time

Acceptable since Extra.Time is allowed through allowedModulePrefixes = [ "Extra" ]

Rejected module imports

module Data.Wrong exposing (Wrong)

import Data.Animal
import Data.Thing
import Page

will get rejected with these errors:

-- ELM-REVIEW ERROR ------------------------------------ src/Data/Wrong.elm:12:1

OnlyImportFromOutside: Cannot `import Data.Animal` from `module Data.Wrong`

12| import Data.Animal
13| import Data.Thing

──────────────────────────────────────────────────────── src/Data/Wrong.elm:13:1

OnlyImportFromOutside: Cannot `import Data.Thing` from `module Data.Wrong`

12| import Data.Animal
13| import Data.Thing
14| import Page

──────────────────────────────────────────────────────── src/Data/Wrong.elm:14:1

OnlyImportFromOutside: Cannot `import Page` from `module Data.Wrong`

13| import Data.Thing
14| import Page

I found 3 errors in 1 file.