nab-provider

Apply Python packaging rules during dependency resolution. This package supplies candidate versions and their dependency constraints to nab-resolver, including environment markers and build, distribution, and VCS policies.

It performs no networking, file access, or subprocess calls.

Package listings and metadata arrive through nab_provider.fetch_port.FetchPort, an interface implemented by the application using the provider. That application is called the host; nab-project supplies it for the nab CLI. nab_provider.testing supplies an in-memory implementation for tests.

When to use it

Use nab-provider to embed nab's resolution in a host that already owns its networking and caching, keeping nab-index out of the import graph. Most users want nab instead.

The API is experimental. Pin an exact version when embedding it.

Wheel tags

wheel_tag_set(filename) caches repeated filename queries. parse_wheel_tag_set(filename) shares parsing by tag suffix for bulk listings.

Value records

Nab's record constructors declare their fields explicitly. nab_provider.value shares value comparison and copying across the provider, index and project layers. Fixed fields use Final annotations; assignment is not checked at runtime. replace() calls the concrete constructor, including validation and derived fields:

from nab_provider.tags import PlatformSpec
from nab_provider.value import replace

platform = PlatformSpec("linux_x86_64")
platform = replace(platform, runs_on_libc=(2, 28))