📝§ Package management and versioning

Package managers are dependency injection mechanisms

Implicit interface

It is preferable to have a single version of each library

• Libraries should not pin specific versions of dependencies

• Libraries should communicate dependencies’ versions constraints

  • Dependencies’ version constraints require additional maintenance work

  • Packages only use a subset of other packages’ interfaces

Interface is second-class for package managers—developers code against library’s interface, but package managers operate on versions

• Version number communicates version of the interface and of its implementation

  • Version numbers version package interface as a whole

• Packages could declare their dependencies’ interface instead of version constraint—a thought experiment