Dependency handling with lockfiles

[svengreb]

The usage of dependency lockfiles like package-lock.json or yarn.lock has always been a controversial topic where opinions go in different directions. On one side many project maintainers tend to argue that it helps to achieve deterministic build results, but on the side it might also hide problems when any later versions of a used dependency, or its transitive dependencies, is not compatible with the own project anymore.

I‘ve investigated a lot of time into research again to finally find a solution that works for my projects. In short, the result is to go with the rule that is also used by many large-scale projects: Do not use lockfiles for multi-consumer projects like libraries but only for single-consumer projects like applications.

Therefore the currently committed yarn.lock file will be removed since this makes no sense for a repository template anyway. See the sections below for some more details about how to decide to use a lockfile or not.

When to use lockfiles

The clear advantage of lockfiles are reproducible builds and the persistence of a running project state. They ensure that a project artifact can be rebuild at anytime using the exact same dependencies, resulting in the exact same artifact, even when the project was not updated in years.
This applies to projects that are focused on building a end-to-end experience like applications and other end-user products.

These are the advantages listed in the official npm documentation about package-lock.json files:

• Describe a single representation of a dependency tree such that teammates, deployments, and continuous integration are guaranteed to install exactly the same dependencies.
• Provide a facility for users to "time-travel" to previous states of node_modules without having to commit the directory itself.
• Facilitate greater visibility of tree changes through readable source control diffs.
• Optimize the installation process by allowing npm to skip repeated metadata resolutions for previously-installed packages.
• As of npm v7, lockfiles include enough information to gain a complete picture of the package tree, reducing the need to read package.json files, and allowing for significant performance improvements.

Like mentioned, npm v7 comes with a lot of advantages and the team recommends to commit the file into project repositories:

• the lockfile has enough information to describe the precise package tree all by itself.
• the lockfile maps the packages to their information by their relative location to the root (instead of their name).
• the npm CLI uses yarn.lock lockfiles if available, as a source of package metadata and resolution guidance when there is missing information, knowing that the package-lock.json is the authoritative definition.
  • yarn.lock lockfiles cannot completely replace npm’s lockfile since the current implementation doesn’t have enough information needed for the complete npm functionality.
• the npm CLI uses a “hidden lockfile“ placed inside the node_module directory that helps to avoid repeated package tree reading.

Another points is that in end-user projects dependencies in package.json files are pinned often instead of using SemVer range selectors like ^ (latest minor-only) or ~ (latest patch only). In such cases a lockfile helps to keep control about transitive dependencies and persist projects states in time.

When to avoid lockfiles

Even though the Yarn team published a blog post in 2016 that states to always commit the yarn.lock file, regardless of the project type, this advice was not adopted by every project and some “real-world scenarios“ often showed that this decision was justified. There are blog posts that summarize when not to use a lockfile where even Yarn maintainers reply with comments that claim the opposite, but over the time more and more projects went away from using lockfiles.
One argument is that lockfiles are important to enure that library contributors in 10 years still know what was the last confirmed set of packages which worked as expected, but this can almost be ignored in a ecosystem like Node that changes almost every day.

Another important point is to mention that the usage of lockfiles were also a attack surface to inject malicious dependencies. Due to the large size of lockfiles, it is also often a challenge for project maintainers to review and validate a lockfile in pull requests are so they are often ignored and blindly trusted.

The community is still not of one opinion and I guess this will never change, but learning about the experience of well-known maintainers and popular projects is often a good way to find the own decision.

In conclusion, the usage of lockfiles in a non-end-user project can be well summarized with “just postponing the inevitable breakage“: