Nearly every popular programming language comes with one or more package managers. The software packages distributed by such package managers form large software ecosystems. These packaging ecosystems contain a large number of package releases that are updated regularly and that have many dependencies to other package releases. While packaging ecosystems are extremely useful for their respective communities of developers, they face challenges related to their scale, complexity, and rate of evolution. Typical problems are backward incompatible package updates, and the risk of (transitively) depending on packages that have become obsolete or inactive.This manuscript uses the libraries.io dataset to carry out a quantitative empirical analysis of the similarities and differences between the evolution of package dependency networks for seven packaging ecosystems of varying sizes and ages: Cargo for Rust, CPAN for Perl, CRAN for R, npm for JavaScript, NuGet for the .NET platform, Packagist for PHP, and RubyGems for Ruby.We propose novel metrics to capture the growth, changeability, resuability and fragility of these dependency networks, and use these metrics to analyse and compare their evolution. We observe that the dependency networks tend to grow over time, both in size and in number of package updates, while a minority of packages are responsible for most of the package updates. The majority of packages depend on other packages, but only a small proportion of packages accounts for most of the reverse dependencies. We observe a high proportion of "fragile" packages due to a high and increasing number of transitive dependencies. These findings are instrumental for assessing the quality of a package dependency network, and improving it through dependency management tools and imposed policies.
Security vulnerabilities are among the most pressing problems in open source software package libraries. It may take a long time to discover and fix vulnerabilities in packages. In addition, vulnerabilities may propagate to dependent packages, making them vulnerable too. This paper presents an empirical study of nearly 400 security reports over a 6-year period in the npm dependency network containing over 610k JavaScript packages. Taking into account the severity of vulnerabilities, we analyse how and when these vulnerabilities are discovered and fixed, and to which extent they affect other packages in the packaging ecosystem in presence of dependency constraints. We report our findings and provide guidelines for package maintainers and tool developers to improve the process of dealing with security issues.
KEYWORDSsoftware repository mining, software ecosystem, dependency network, security vulnerability, semantic versioning ACM Reference Format: Alexandre Decan, Tom Mens, and Eleni Constantinou. 2018. On the impact of security vulnerabilities in the npm package dependency network. In
The semantic versioning (semver) policy is commonly accepted by open source package management systems to inform whether new releases of software packages introduce possibly backward incompatible changes. Maintainers depending on such packages can use this information to avoid or reduce the risk of breaking changes in their own packages by specifying version constraints on their dependencies. Depending on the amount of control a package maintainer desires to have over her package dependencies, these constraints can range from very permissive to very restrictive. This article empirically compares semver compliance of four software packaging ecosystems (Cargo, npm, Packagist and Rubygems), and studies how this compliance evolves over time. We explore to what extent ecosystem-specific characteristics or policies influence the degree of compliance. We also propose an evaluation based on the "wisdom of the crowds" principle to help package maintainers decide which type of version constraints they should impose on their dependencies.
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