Building Pre-release Versions

By default, fromager ignores pre-release versions (alpha, beta, release candidate) when resolving package dependencies. Versions with a, b, or rc components are only considered when explicitly requested.

This behavior follows Python packaging standards and ensures that stable versions are preferred unless pre-release versions are specifically needed.

Pre-release detection is handled on a package-by-package basis. This means you can mix stable and pre-release requirements in the same build - some packages can use stable versions while others use pre-release versions. This flexibility is useful when you need to test with a pre-release version of one specific package without affecting the rest of your dependency tree.

There are two ways to include pre-release versions in your builds:

Method 1: Include Pre-release in Requirements

You can specify pre-release versions directly in your requirement specification by including the pre-release version in the version specifier:

$ fromager bootstrap "mypackage>=1.0a1"

This tells fromager that pre-release versions are acceptable for this package, and it will consider alpha versions 1.0a1 and later.

Examples:

# Build a specific pre-release version
$ fromager bootstrap "django==4.2.0b1"

# Allow any pre-release version above a threshold
$ fromager bootstrap "numpy>=1.25.0rc1"

# Mix stable and pre-release requirements
$ fromager bootstrap "requests>=2.28.0" "django==4.2.0b1"

Method 2: Use Constraints File

Alternatively, you can enable pre-release versions through a constraints file.

Create a constraints file (e.g., constraints.txt) with the pre-release version:

mypackage==1.0rc3

Then run fromager with the constraints file:

$ fromager --constraints-file constraints.txt bootstrap mypackage

Example with conflicting stable requirement:

If you have a requirement that specifies a version range but want to use a pre-release within that range:

constraints.txt

flit-core==2.0rc3

$ fromager --constraints-file constraints.txt bootstrap "flit-core<2.0.1"

Even though the requirement flit-core<2.0.1 would normally resolve to the latest stable version (e.g., 2.0), the constraint forces the use of the pre-release version 2.0rc3.