SPM - Package contains revisioned dependencies

Question

I am trying to install the MongoDB swift driver using the swift package driver. I followed their instructions and installed the mongo-c-driver using home-brew. I then created a new directory and within a new project using:

swift package init --type executable

I then added the dependencies to the Package.swift file.

When trying to run any command that summonsswift package resole in the directory, i get the following error:

error: the package PackageReference(identity: "mongo-swift-driver", name: nil, path: "https://github.com/mongodb/mongo-swift-driver.git", isLocal: false) @ 0.0.2 contains revisioned dependencies:

PackageReference(identity: "swift-bson", name: nil, path: "https://github.com/mongodb/swift-bson", isLocal: false) @ master

PackageReference(identity: "swift-mongoc", name: nil, path: "https://github.com/mongodb/swift-mongoc", isLocal: false) @ master

I made sure that everything is up to date and that the first line of the Package.swift is // swift-tools-version:4.0

I would like to know what these revisioned dependencies are, as i have not found anything useful. And how this error can be resolved.

Answer 1

The Swift Evolution proposal that introduced the ability to specify branches instead of revisions in SPM packages (SE-0150 says this:

While this feature [specifying branches] is useful during development, a package's dependencies should be updated to point at versions instead of branches before that package is tagged for release. This is because a released package should provide a stable specification of its dependencies, and not break when a branch changes over time. To enforce this, it is an error if a package referenced by a version-based dependency specifies a branch in any of its dependencies.

It looks like the version 0.0.2 of the parent package that you're using did not follow the rule to switch to specific versions for its dependencies and SPM doesn't allow this.

If possible, you should try to use a newer version of the parent package that fixes this issue. If a newer version doesn't exist, you may have to override the dependency and fix it yourself (I believe you can use swift package edit to do that — or fork the dependency and point to your own repo, of course.)