How do you fix this circular dependency issue in node

Question

` I'm getting errors such as Type variable is undefined and getLastUnknownAlbumTrackNumber is not a function

I installed madge to check circular dependencies but I dont know how to resolve them

following is the output from madge

const madge = require('madge');

madge('./server.js').then((res) => {
    console.log(res.circular());
});

OUTPUT:
(node:6960) Warning: Accessing non-existent property 'getLastUnknownAlbumTrackNumber' of module exports inside circular dependency
(node:6960) Warning: Accessing non-existent property 'Type' of module exports inside circular dependency
[
[ 'jobs/index.js', 'models/index.js' ],
[ 'models/index.js', 'services/metadata.js' ]
]

The following are the related imports & exports

jobs/index.js

const { getMovieMetaData, getTVShowMetaData, getAlbumMetaData } = require('../models');
...
module.exports = { getAll, upsertAll, getLastUnknownAlbumTrackNumber }

services/metadata.js

const { Type } = require('../models');
...
module.exports = Metadata

models/index.js

const { getLastUnknownAlbumTrackNumber } = require('../jobs');
const metadataServiceConstructor = require('../services/metadata');
const metadataService = new metadataServiceConstructor()
...
module.exports = { Type, getMovieMetaData, getTVShowMetaData, getAlbumMetaData }

jobs includes models which includes jobs. That's your circular dependency. Can't do that in nodejs. Refactor to move the common stuff to a third module that both those modules can then include without including each other. It does you absolutely no good to use madge here. You know where your circular dependency is now - refactor to fix it. — jfriend00, Jul 07 '21 at 04:37
Oh, and models includes metadata which includes models too. Can't do that either. — jfriend00, Jul 07 '21 at 04:51

score 1 · Accepted Answer · answered Jul 07 '21 at 04:29

What do you expect to happen? An attempt to resolve a circular import would result in infinite recursion.

Even if you're using this tool to check for circular imports, it's not static analysis, so the code still needs to be run, hence you encounter the same issue.

As a side note, why are you using this tool at all? It's clear where the circular import lies. You need to refactor to avoid this.

score 0 · Answer 2 · answered Jan 11 '23 at 15:55

At first read, this answer may seem a bit cryptic
This is due to nature of cyclic dependency.

Once you understand it, it will be easy to fix your solution too

Issue:

1.js -> 2.js -> 3.js
                3.js -> 4.js -> 2.js ( `cycle` )

Solution that worked:

1.js -> 2.js `(remove connection)`
               3.js -> 4.js -> 2.js
1.js -> `200.js (add new)` -> 3.JS

How do you fix this circular dependency issue in node

2 Answers2