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commit 2419027e35d64ea396d6d108deb8000ceeb0c62f
parent 0d03586eb1d530992a3871fb643b0e95215b922a
Author: Luís Ferreira <>
Date:   Mon, 31 Jan 2022 01:56:35 +0000

feat(content/posts): add post about lockfile in libraries

Signed-off-by: Luís Ferreira <>

Acontent/posts/ | 188+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 188 insertions(+), 0 deletions(-)

diff --git a/content/posts/ b/content/posts/ @@ -0,0 +1,188 @@ +--- +title: 'The controversy and misconception around package managers lockfile in +libraries' +date: '2022-01-31T00:48:00+01:00' +tags: ['lockfiles', 'package-managers', 'packaging', 'dependencies', +'reproducible-builds', 'reproducible', 'deterministic'] +description: "This post describes the common misconception and controversy +around package managers philosophy about the abomination of lockfiles in +packages, more specifically in libraries." +--- + +**NOTE:** I'm making this because I feel like this should be clarified. I had a +lot of discussions where people were biased by other opinions, mostly due to +spread misconceptions about these files. I can update this later with a more +fundamental reason if I see even more controversy on discussions I have in a +near future. + +A lot of package managers use a lockfile mechanism to reliably reproduce their +packages across different environments. This mechanism is used when other +environments build packages that do not use pinned dependency versions and end +up using a modified version compatible with the version expression specified in +the package manifest file. + +## But what is a lock file? + +A lockfile is normally a generated file by the package manager that contains +the information about the exact versions currently used to build a package +successfully the way is intended to be. Some lockfiles include other metadata +about the package used such as checksums to ensure integrity. + +### Advantages + +One of the biggest advantages is to make deterministic dependency resolution. +This way, package managers can more easily replicate the same builds on +different environments. With that, you can also build your own package more +consistently. Both help users and developers seeking problems and can decrease +test suite failures on development. + +### Security risk + +It is straightforward to understand the advantages of a lockfile but some +people don't understand the _" disadvantages"_ and intentionally skip lockfiles +review, which is a tremendously bad idea; let me explain to you why. + +For example, GitHub has a bad security issue related to detached references +that allow any user to create a fork of the repo and associate a commit to the +original repo. See the example of Linus Torvalds' `linux` mirror with +[this]( +commit. Because git obviously allows anyone to create commits with any email, +GitHub automatically associates it as the real Linus Torvalds. So a user can +easily create a security vulnerability, bump a patch version and change the +commit hash on the lockfile accordingly, making it a poisoned environment, +without being too obvious. + +Another problem related to other external services can rise. The problem here +is trusting the source and the underlying service, falling into accepting +changes that can't be easily verified by just looking at it. Should we trust +any commit coming from ``? Yes, but apparently not. + +This can be mitigated using GPG signatures. Linux releases, for example, are +all signed by a group of trusted keys. That way we can trust that release tag +by verifying the underlying signature. + +Therefore committing these files should be made and reviewed with caution and +in a trusted environment. + +## You might say, why not pin the versions, instead? + +Well, if [semantic versioning]( standard is strictly +followed by the package maintainers, breaking changes wouldn't be a big of a +deal, although, the package will always be different. In a real-world +situation, breaking changes happen all the time, even if the intention is only +a bug fix. Sometimes things get out of control and because of today's systems +complexity, regression bugs can easily happen. + +However, specifying a version range covering patches or minor versions is more +practically useful for a situation where the latest non-breakable version is +preferable. + +Also, just pinning versions doesn't solve integrity issues and lockfiles does. + +## Why reproducible builds are important? + +Quoting Reproducible Builds project: + +> The motivation behind the Reproducible Builds project is therefore to allow +> verification that no vulnerabilities or backdoors have been introduced during +> this compilation process. By promising identical results are always generated +> from a given source, this allows multiple third parties to come to a +> consensus on a “correct” result, highlighting any deviations as suspect and +> worthy of scrutiny. + +You can read more about the project and their motivation along with tools to +make your builds more reproducible, [here]( + +## The controversy and misconception part + +Here is where the rant starts. A lot of package managers and maintainers have, +behind them, a strong philosophy about not including lockfiles for libraries. +This is something I can't really understand, given the rationale. + +For example, the Rust package manager, Cargo, doesn't generate lockfiles by +default for libraries: + +> This property is most desirable from applications and packages which are at +> the very end of the dependency chain (binaries). As a result, it is +> recommended that all binaries check in their Cargo.lock. +> +> For libraries the situation is somewhat different. A library is not only used +> by the library developers, but also any downstream consumers of the library. +> Users dependent on the library will not inspect the library’s Cargo.lock +> (even if it exists). This is precisely because a library should not be +> deterministically recompiled for all users of the library. + +You can read more about this on "The Cargo Book", +[here]( + +The last sentence is just wrong. Libraries should indeed be deterministically +recompiled to ensure consistency. That might not be true for the end-user, but +this is essential for the library developers to detect if an introduced change +caused problems. Essentially, packages should test their environment against +their supported version ranges and their locked reproducible environment. +Testing only one of those is wrong, and that is probably the root of the +misconception. + +Many other package managers do claim the same thing and it seems they justify +themselves with each other claims. The worst part is the fact that some +maintainers decline including lockfiles in their projects and others create +pull requests/issues requesting to remove lockfiles, without thinking logically +about the problem and consequences, hence my frustration. + +Fortunately, there is some clarification articles out there, including +[yarn]( blog +post and [Shalvah's blog +post]( that you should +check out, although there is a lot of bold claims that don't make sense. + +From +[sindresorhus/ama/issues/479]( + +> The lockfile defeats the whole purpose of the caret ^ that is the default +> save behavior. And it prevents us from getting security patches immediately, +> which is insane. There are more good updates than bad updates, so it does +> more harm than good. The idea that it protects us from malicious code is +> silly because there's no way in hell that people are actually auditing the +> entire dependency graph when they do finally get around to updating the +> lockfile. It's a fallacy that leads to a false sense of security. + +Lockfiles are NOT there to prevent security issues, they are there to reproduce +environments. If you rely on lockfiles for security, you are doing it wrong. +Nothing prevents you from ignoring the lockfile as a user and you should patch +upstream if there is a security issue on some dependency. As a developer you +might want to proactively update that file, but also keep them to reproduce +your application/library. + +From [, When not to use +package-lock.json]( + +> The origin of this misuse is NPM documentation. It should instead explain +> that package-lock.json should only be committed to the source code version +> control when the project is not a dependency of other projects, i.e. +> package-lock.json should only by committed to source code version control for +> top-level projects (programs consumed by the end user, not other programs). +> +> [...] +> +> I would support a variation of package-lock.json if it could somehow only +> apply to devDependencies. I can see some (albeit small and with tradeoffs) +> benefit to wanting your development environment not break if there is a +> broken release among your dependencies. + +Testing only with lockfiles is wrong, as well as living in the bleeding edge +world by testing only with the latest version. You should test both or ideally, +all the versions your manifest file supports. Only covering `devDependencies` +is also a claim that makes zero sense. Normal `dependencies` may not be part of +the build process but of the execution/runtime part of your +application/library, and should indeed be reproducible. + +## Conclusion + +The conclusion is simple, please consider using a lockfile. Don't assume that +semantic versioning is followed strictly because that is utopic. Also, make +your testsuite deterministic and wide to your dependency requirements. Someone +from the outside will touch your library, possibly try to contribute and +complain about their testsuite failing due to an unknown +[Heisenbug](, +most likely a side effect caused by a dependency, conducting an effort to +discover a problem, just because you are against lockfiles.