cdk-multiple-lock-file-bundling

name	cdk-multiple-lock-file-bundling
description	Fix AWS CDK bundling failures caused by multiple package lock files in the same project. Use when: (1) CDK synth/deploy fails with "ValidationError: Multiple package lock files found: pnpm-lock.yaml, package-lock.json", (2) NodejsFunction or other bundled Lambda fails during cdk synth, (3) CI pipeline fails on test stage with CDK bundling errors. Covers determining which lock file to keep based on project's actual package manager.
author	Claude Code
version	1.0.0
date	2026-01-27T00:00:00.000Z

CDK Multiple Lock File Bundling Error

Problem

AWS CDK's NodejsFunction bundling fails when multiple package manager lock files exist in the repository. The error message doesn't indicate which package manager the project actually uses, requiring investigation.

Context / Trigger Conditions

• Error: ValidationError: Multiple package lock files found: pnpm-lock.yaml, package-lock.json
• Occurs during cdk synth, cdk deploy, or test runs that synthesize CDK stacks
• CI pipeline fails on build/test stages with CDK bundling
• Recently merged code from another contributor who uses a different package manager

Solution

Step 1: Identify the Project's Package Manager

Check for these indicators (in order of reliability):

# 1. Check for packageManager field in root package.json
grep -o '"packageManager"[^,]*' package.json

# 2. Check which lock file is in .gitignore (the OTHER one should be used)
grep -E "package-lock|pnpm-lock|yarn.lock" .gitignore

# 3. Check CI configuration for which package manager is used
grep -E "npm |pnpm |yarn " .gitlab-ci.yml .github/workflows/*.yml 2>/dev/null

# 4. Check scripts in package.json for package manager hints
grep -E "npm run|pnpm |yarn " package.json

Step 2: Remove the Incorrect Lock File

# If project uses npm (has package-lock.json as source of truth):
git rm pnpm-lock.yaml  # or yarn.lock

# If project uses pnpm (has pnpm-lock.yaml as source of truth):
git rm package-lock.json

# If project uses yarn (has yarn.lock as source of truth):
git rm package-lock.json pnpm-lock.yaml

Step 3: Prevent Future Occurrences

Add the unwanted lock files to .gitignore:

# For npm projects, add:
echo "pnpm-lock.yaml" >> .gitignore
echo "yarn.lock" >> .gitignore

# For pnpm projects, add:
echo "package-lock.json" >> .gitignore
echo "yarn.lock" >> .gitignore

Step 4: Commit and Verify

git add -A
git commit -m "fix: remove incorrect lock file for CDK bundling"
# Run CDK synth to verify
npx cdk synth

Verification

After removing the incorrect lock file:

1. npx cdk synth completes without bundling errors
2. CI pipeline passes the test stage
3. Only one lock file exists in the repository

Example

Scenario: CI fails with this error after merging a PR:

ValidationError: Multiple package lock files found: pnpm-lock.yaml, package-lock.json.
Please ensure that only one of these files is present.

Investigation:

$ grep packageManager package.json
# No output - not defined

$ grep -E "npm|pnpm" .gitlab-ci.yml
  - npm ci
  - npm run build

$ ls *.lock* package-lock.json
package-lock.json  pnpm-lock.yaml

Resolution: Project uses npm (based on CI config). Remove pnpm-lock.yaml:

git rm pnpm-lock.yaml
git commit -m "fix: remove pnpm-lock.yaml from npm project"

Notes

• This commonly happens when contributors use different package managers locally
• pnpm automatically creates pnpm-lock.yaml when running any pnpm command
• Some IDEs auto-run package managers, creating unexpected lock files
• CDK's esbuild bundler is strict about having exactly one lock file
• The error occurs at synth time, not deployment time

Related

• See also: cdk-temp-folder-disk-bloat (another CDK bundling issue)