[Bug]: Impossible to delete metadata fields from variant, if there is more than 1 field

[ufoch]

Package.json file

{
  "name": "@dtc/backend",
  "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",
    "start": "medusa start",
    "dev": "medusa db:migrate && medusa develop",
    "lint": "medusa lint",
    "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=false --runInBand --forceExit",
    "test:unit": "TEST_TYPE=unit NODE_OPTIONS=--experimental-vm-modules jest --silent --runInBand --forceExit"
  },
  "dependencies": {
    "@medusajs/admin-sdk": "2.17.2",
    "@medusajs/admin-shared": "2.17.2",
    "@medusajs/caching": "2.17.2",
    "@medusajs/cli": "2.17.2",
    "@medusajs/dashboard": "2.17.2",
    "@medusajs/draft-order": "2.17.2",
    "@medusajs/framework": "2.17.2",
    "@medusajs/medusa": "2.17.2",
    "@medusajs/ui": "4.1.15",
    "@tanstack/react-query": "5.64.2",
    "react-i18next": "13.5.0",
    "react-router-dom": "6.30.3",
    "zod": "4.2.0"
  },
  "devDependencies": {
    "@medusajs/test-utils": "2.17.2",
    "@swc/core": "^1.7.28",
    "@swc/jest": "^0.2.36",
    "@types/jest": "^29.5.13",
    "@types/node": "^20.12.11",
    "@types/react": "^18.3.2",
    "@types/react-dom": "^18.2.25",
    "jest": "^29.7.0",
    "prop-types": "^15.8.1",
    "react": "^18.3.1",
    "react-dom": "^18.3.1",
    "ts-node": "^10.9.2",
    "typescript": "^5.6.2",
    "vite": "^5.4.14",
    "yalc": "^1.0.0-pre.53"
  },
  "engines": {
    "node": ">=20"
  },
  "packageManager": "npm@11.15.0"
}

Node.js version

v22.22.3

Database and its version

PostgreSQL 16.14 (Debian 16.14-1.pgdg13+1)

Operating system name and version

Ubuntu 24.04.4 LTS

Browser name

No response

What happended?

It's not possible to delete a variant.metadata property using the empty string method form the docs, if the field to delete is not the last metadata field (i. e. the total metadata field count is greater than 1). Deletion of the last variant.metadata field seems to be handled differently and works.

It works perfectly for product.metadata, customer.metadata and cart.items.metadata (all tested).

I would be very thankful for a fix.

Expected behavior

Deleting a variant.metadata field by assigning an empty string should remove the property as described in the docs (also if there is more than 1 variant.metadata field).

If the field to delete is the last variant.metadata field, the deletion works, so the bug is only reproducible with more than 1 field present.

Actual behavior

The property doesn't get deleted and instead variant.metadata contains the property with the empty string value, i. e. "propertyName": "".

Link to reproduction repo

The bug occurs in any fresh v2.17.2 project; just add two test properties to any variant metadata and try to delete one of them afterwards; the optimistic UI update works, but persistent deletion doesn't

[medusa-os-bot]

Thanks for reporting this! We've labeled it as a bug and will investigate.

Reporter identifies that deleting a product variant metadata field by setting it to an empty string (as documented) fails silently when the variant has more than one metadata key — the key is persisted with an empty string value instead of being removed. Bug is confirmed in the codebase: the variant update path calls upsertWithReplace in ProductModuleService.updateVariants_ (packages/modules/product/src/services/product-module-service.ts:704) without invoking mergeMetadata, which is the utility responsible for stripping empty-string keys. Product, customer, and cart item metadata updates all invoke mergeMetadata correctly (via ProductRepository.deepUpdate or MedusaInternalService.update), explaining why those work. Fix requires adding metadata merging to the variant update path before upsertWithReplace is called. Affects v2.17.2; report includes full reproduction steps.