[Bug]: Can not check out with items from different stock locations even if they are stocked

[damianr13]

Package.json file

{
  "name": "medusa-starter-default",
  "version": "0.0.1",
  "description": "A starter for Medusa projects.",
  "author": "Medusa (https://medusajs.com)",
  "license": "MIT",
  "keywords": [
    "sqlite",
    "postgres",
    "typescript",
    "ecommerce",
    "headless",
    "medusa"
  ],
  "scripts": {
    "build": "medusa build",
    "seed": "medusa exec ./src/scripts/seed.ts",
    "start": "medusa start",
    "dev": "medusa develop",
    "test:integration:http": "TEST_TYPE=integration:http NODE_OPTIONS=--experimental-vm-modules jest --silent=false --runInBand --forceExit",
    "test:integration:modules": "TEST_TYPE=integration:modules NODE_OPTIONS=--experimental-vm-modules jest --silent --runInBand --forceExit",
    "test:unit": "TEST_TYPE=unit NODE_OPTIONS=--experimental-vm-modules jest --silent --runInBand --forceExit"
  },
  "dependencies": {
    "@medusajs/admin-sdk": "2.1.1",
    "@medusajs/cli": "2.1.1",
    "@medusajs/framework": "2.1.1",
    "@medusajs/medusa": "2.1.1",
    "@mikro-orm/core": "5.9.7",
    "@mikro-orm/knex": "5.9.7",
    "@mikro-orm/migrations": "5.9.7",
    "@mikro-orm/postgresql": "5.9.7",
    "awilix": "^8.0.1",
    "pg": "^8.13.0"
  },
  "devDependencies": {
    "@medusajs/test-utils": "2.1.1",
    "@mikro-orm/cli": "5.9.7",
    "@swc/core": "1.5.7",
    "@swc/jest": "^0.2.36",
    "@types/jest": "^29.5.13",
    "@types/node": "^20.0.0",
    "@types/react": "^18.3.2",
    "@types/react-dom": "^18.2.25",
    "jest": "^29.7.0",
    "prop-types": "^15.8.1",
    "react": "^18.2.0",
    "react-dom": "^18.2.0",
    "ts-node": "^10.9.2",
    "typescript": "^5.6.2",
    "vite": "^5.2.11"
  },
  "engines": {
    "node": ">=20"
  }
}

Node.js version

v22.11.0

Database and its version

PostgreSQL 16.2

Operating system name and version

MacOS Sonoma 14.6.1

Browser name

No response

What happended?

If I have different stock locations for my products, I can't check out 2 products that are stocked in different locations even when both locations are connected to the same sales channel.

I attached a public repository with a test that showcases the issue.

Expected behavior

Checking out items from different stock locations should work.

Actual behavior

The cart does not complete. I tracked it down to the following function:
https://github.com/medusajs/medusa/blob/v2.1.1/packages/core/core-flows/src/cart/utils/prepare-confirm-inventory-input.ts

In here all the stock locations are added to all the items even if each of the items are "contributing" different stock locations to the list.

Later this value is used here:
https://github.com/medusajs/medusa/blob/v2.1.1/packages/core/core-flows/src/cart/steps/reserve-inventory.ts

And we simply select the first location for all the items.

Link to reproduction repo

https://github.com/damianr13/medusa-cart-different-stock-locations