Resolving NPM/Yarn Dependency Conflicts

Identifying Dependency Conflicts

Common signs of dependency conflicts:

• ERESOLVE errors during installation
• Cannot find module errors at runtime
• Multiple versions of same package in node_modules
• Unexpected behavior or missing features

Step-by-Step Solutions

1. Basic Conflict Resolution

For npm:

npm install --legacy-peer-deps  # Temporary workaround
npm dedupe                     # Attempt to reduce duplicates

For Yarn:

yarn install --flat            # Identify conflicts
yarn why <package-name>        # Check why a package is included

2. Force Clean Installation

# Remove existing installations
rm -rf node_modules package-lock.json yarn.lock

# Reinstall (pick one)
npm install
# OR
yarn install

3. Manual Version Resolution

Edit package.json to specify exact versions:

{
  "dependencies": {
    "react": "18.2.0",  // Exact version
    "lodash": "^4.17.21" // Caret range
  },
  "resolutions": {  // Yarn specific
    "react-dom": "18.2.0"
  }
}

4. Advanced Techniques

Using Yarn resolutions (for Yarn only):

{
  "resolutions": {
    "**/react": "18.2.0",
    "**/react-dom": "18.2.0"
  }
}

For npm (v8+):

npm install --package-lock-only
npm install --omit=peer

5. Check Dependency Tree

npm ls <package-name>  # Show dependency tree
# OR
yarn list --pattern <package-name>

Prevention Strategies

1. Use consistent version specifiers:

• ~1.2.3 = patch updates only
• ^1.2.3 = minor updates
• 1.2.3 = exact version

1. Regularly update dependencies:

   npm outdated
   # OR
   yarn outdated

3. Use lockfiles:

• Commit package-lock.json or yarn.lock
• Ensures reproducible installs

3. Consider monorepo tools:

• Lerna
• Nx
• Yarn Workspaces

Common Conflict Patterns

React Duplicates

# Often shows as multiple React versions
npm ls react
# Solution: Ensure all React packages use same version

Babel/Webpack Plugins

# Version mismatch between core and plugins
yarn why @babel/core
# Solution: Match major versions

Peer Dependencies

# Common with React libraries
npm install --legacy-peer-deps
# OR specify correct peer dependency versions